The 46th Annual Meeting of the European Society for Blood and Marrow Transplantation: Physicians Poster Session (P001-P706) (2024)

¹Universitiy Medical Center Augsburg, Augsburg, Germany, ²EBMT Paris Study Office, Hôpital Sain-Antoine, Paris, France, ³INSERM UMR 938, Sorbonne University, Paris, France, ⁴Hospital Clinic, Barcelona, Spain, ⁵University Hospital Eppendorf, Hamburg, Germany, ⁶Erasmus MC Cancer Institute, University Medical Center, Rotterdam, Netherlands, ⁷Oslo University Hospital, Oslo, Norway, ⁸University Hospital Maastricht, Maastricht, Netherlands, ⁹University of Freiburg, Freiburg, Germany, ¹⁰Nijmegen Medical Centre, Nijmegen, Netherlands, ¹¹University Medical Center Utrecht, Utrecht, Netherlands, ¹²University Hospital Essen, Essen, Germany, ¹³Universitätsklinikum Ulm, Ulm, Germany, ¹⁴Chaim Sheba Medical Center, Tel Aviv University, Tel-Hashomer, Israel

Background: Acute myeloid leukemia with RUNX1 gene mutation (RUNX1+ AML) has been proposed as a provisional entity in the 2016 WHO classification. Inferior response rates and outcome after conventional chemotherapy have been detected in patients with RUNX1 gene mutation and accordingly, RUNX1+ AML is allocated in the unfavorable prognostic category of the 2017 European Leukemia Net classification. Following allogeneic stem cell transplantation (alloSCT), RUNX1 mutation was an unfavorable factor in one study in MDS/secondary AML, while data in de novo AML are scarce. In this retrospective study by the EBMT Acute Leukemia Working Party, we elucidate the prognostic value of RUNX1 mutation in patients undergoing alloSCT for AML in first complete remission (CR1).

Methods: Adults undergoing alloSCT for AML in CR1 from matched related or unrelated donors between 2013 and 2018 with complete information on conventional cytogenetics and RUNX1 mutational status were selected from the EBMT registry. Variables of interest were overall and leukemia-free survival (OS/LFS), GvHD/relapse free survival (GRFS), cumulative relapse incidence (RI), non-relapse mortality (NRM) and GvHD. Log rank test, Gray test and Cox regression models were used for statistical analysis.

Results: A total of 516 patients were included, 128 RUNX+ and 388 RUNX-, with >80% of both subgroups presenting as de novo AML. As expected, RUNX1+ patients rarely had co-mutations in NPM1 (6% vs. 26%, p=10^-3), and showed a positive correlation with ASXL1 mutations (50% vs. 16%, p=10^-4). Cytogenetic categories and other mutations (FLT3-ITD, CEBPA) were equally distributed between the two groups, as were age, donor and graft type, CMV, conditioning and T cell depletion (TCD).

Median follow-up was 16.4 (RUNX+) and 19.8 (RUNX-) months. 2y OS/LFS of the entire cohort were 64% [59-69]/57% [52-62], with no difference between RUNX1+ and RUNX1- patients either in univariate or multivariate analysis (2y OS: 67.9% [57.3-78.5] vs. 63.1%v[57.4-68.7]p=0.15; 2y LFS: 57.6% [46.4-68.7] vs. 57% [51.4-62.6], p=0.38]). RUNX1 mutation neither had any impact among patients with normal karyotype. Furthermore, no other outcome parameter was influenced by RUNX1 mutational status. Instead, multivariate analysis revealed age and donor type as risk factors for OS, LFS and NRM. Poor cytogenetic was associated with higher RI and inferior LFS/GRFS, in vivo TCD with a lower rate of aGvHD II-IV, cGvHD, and better GRFS. Among patients with available information, FLT3-ITD was an independent risk factor for relapse, LFS and GRFS. RUNX1 did not modify the role of FLT3-ITD.

Conclusions: Within the limits of a retrospective registry analysis, we could not find a negative influence of RUNX1 mutation on outcome after allogeneic SCT in CR1. Hence, transplantation in CR1 might overcome the unfavorable prognostic value of RUNX1 mutation and can be recommended as consolidation treatment in this entity.

Disclosure: Nothing to declare.

¹OPBG, Roma, Italy, ²EBMT ALWP Office, Saint Antoine Hospital, Paris, France, ³San Martino, Genova, Italy, ⁴Paoli-Calmettes Institute, Inserm CBT1409, Marseille, France, ⁵San Raffaele Hospital, Milano, Italy, ⁶BMT Unit, Antalya, Turkey, ⁷BMT Unit, Madrid, Spain, ⁸HUMANITAS Cancer Center, Milano, Italy, ⁹BMT Unit, Torino, Italy, ¹⁰BMT Unit, Anadolu, Turkey, ¹¹BMT Unit, Rome, Italy, ¹²Sheba University Hospital, Tel Aviv, Israel, ¹³Saint Antoine Hospital, Paris, France

Background: Graft failure (GF) is a life threatening complication following hematopoietic stem cell transplantation (HSCT). Its incidence depends on multiple parameters including type of donor, HLA disparity, stem cell source, graft composition and conditioning regimen. Incidence of GF in T-cell-depleted haploidentical-transplantations (Haplo-HSCT) can reach up to 10-20%. The use of Haplo-HSCT with post-transplant-cyclophosphamide (PTCy) as graft-versus-host-disease (GVHD) prophylaxis is a new standard in the treatment of hematological diseases. Paucity of data exists on GF in Haplo-HSCT with-PTCy.

Methods: To evaluate the incidence and risk factors of GF after Haplo-HSCT with-PT-Cy, we analyzed 1270 adults with acute myeloid leukemia (AML) reported to ALWP-EBMT who received a first Haplo-HSCT from 2010-2018. GF was defined as neutrophil count lower than 500 micro/L at day+45, competing risk was death without engraftment.

Results: Disease status was CR1 in 73% of patients and CR2 in the remaining. Secondary AML was reported in 13.7%. Median follow-up is 22 months and median age at Haplo-HSCT 54 years. Stem cell source was bone marrow (BM) in 41.4% and 44.6% of patents received a myeloablative conditioning regimen (MAC) with TBF(thiotepa, Bulsulfan and Fludarabine) in 59%. PT-Cy in association with calcineurin inhibitors and MMF was the most frequent GVHD-prophylaxis. Cumulative incidence of GF was 6.6 % (95%CI:5.3-8.1), median time to engraftment was 19(1-45) days. Nine patients engrafted after day+45(47-79), 43 patients experienced primary GF and 41 died before day+45 with no sign of donor engraftment. Of the 43 patients with GF, 7 subsequently engrafted after day+45, 29 patients were rescued with a second HSCT. Overall 18 patients are alive at last fu, 2y OS being 32%. CI of engraftment was lower in patients transplanted for secondary AML (91% vs 94%, p=0.003) and was 95% in MAC versus 92.6% in RIC, p< 0.001. CI of day-100 grade II-IV and grade III-IV aGVHD was 29.1 % (95% CI: 26.5 - 31.6) and 10.4 % (95% CI: 8.7 - 12.2), respectively, and 2 years chronic and extensive GVHD was 31.6 % (95% CI: 28.6 - 34.6) and 11.5 % (95% CI: 9.5 - 13.7). At 2 years GRFS, LFS, and OS were 47.1 % (95% CI: 43.9 - 50.2), 55.8 % (95% CI: 52.7-59) and 61 % (95% CI: 57.9-64.1), respectively. Two-year CI of relapse and NRM were 21.2 % (95% CI: 18.7-23.8) and 23 % (95% CI: 20.4-25.6). Disease recurrence was the most common cause of death, with infections and GVHD being the most frequent transplant related causes. In multivariate analysis, factors independently associated with the risk of GF were: secondary-AML (HR 1.28, p=0.007), use of RIC (HR 1.32, p< 0.001), and use of BM (HR 1.21, p=0.002). RIC and adverse cytogenetic risk were associated with relapse and age, performance status and cytogenetic risk with OS.

Conclusions: Incidence of GF after haplo-HSCT with PT-Cy is lower than in T-cell depleted Haplo. Optimization of conditioning regimen and graft source should be considered for reducing the risk GF in Haplo-HSCT recipients using PT-Cy. Comparison of GF in the different platforms of GVHD prevention (PT-Cy and ATG) is warranted.

Disclosure: Nothing to declare.

¹Hospital Puerta de Hierro Majadahonda, Majadahonda, Spain, ²Memorial Sloan Kettering Cancer Center, New York, NY, United States, ³Son Espases University Hospital, IdISBa, Palma de Mallorca, Spain, ⁴University of Milano-Bicocca, Milan, Italy, ⁵Hospital Vall d’Hebron, Barcelona, Spain, ⁶IDIVAL, Santander, Spain

Background: Several prognostic models to stratify allogeneic hematopoietic cell transplantation (allo-HCT) outcomes have been developed in recent years. Despite evidence that minimal residual disease (MRD) is an independent predictor of survival in patients with AML, MRD is excluded from most models. Two novel AML-specific disease scores that incorporate disease data, AML-specific disease risk group (AML-DRG) and AML-HCT-CR, have been shown to be predictive of survival in patients with AML who received an of unmodified HCT (Piyanuch et al. BBMT. 2019). T cell depletion (TCD) using ex vivo CD34 selection has been shown to decrease acute and chronic GVHD without increasing relapse in selected patients with AML, ALL and MDS, and results of a completed phase 3 trial are pending (NCT02345850). Our proposal is to validate both scoring systems in a cohort of patients who underwent ex vivo CD34 selected HCT.

Methods: We included 279 patients age > 18 years who underwent a first CD34+ selected allo-HCT for AML between 2008 and 2018 and calculated their AML-DRG and AML-HCT-CR scores. AML-DRG variables included: secondary AML, adverse European LeukemiaNet2017 genetic risk and MRD status. The AML-HCT-CR model also included HCT-CI score ≥ 3 and age ≥ 60 years. MRD was assessed pre HCT by flow cytometry and/or PCR or NGS as indicated. The primary outcome was survival (OS) and secondary outcomes were progression-free-survival (PFS), and incidences of non-relapsing mortality (NRM), and relapse.

Results: Median age was 55 years (range 19 to 73 years), 45.5% (n = 127) were females and median HTC-CI was 2. All patients received myeloablative conditioning. At time of HCT 20.8% patients had MRD+ status and 5.4% had active disease (Table 1). Median follow-up was 5.5 years (95% CI: 5.1-6.3). For the AML-DRG model, the 3-year OS in the low, intermediate, and high-risk groups were 65%, 52%, and 13%, respectively. PFS at 3 years were 63%, 43%, and 15% in the same groups. The OS predictive accuracy measured by c-statistic was 0.588. In the AML-HCT-CR model, patients in low, intermediate, high risk and very high risk had a 3 year OS of 72%, 58%, 39%, and 51%, respectively. The corresponding PFS at 3 years were 68%, 56%, 36% and 43%. The OS predictive accuracy measured by c-statistic was 0.615. Both scores significantly predicted relapse incidence (AML-DRG model p value= < 0.001; AML-HCT-CR model p value= 0.04), but AML-DRG model was not associated with NRM (p = 0.993).

Conclusions: The AML-DRG and AML-HCT-CR models are predictive of outcomes including OS, PFS, and relapse incidence in a large cohort of patients receiving TCD HCT with CD34+ selected allografts. These data should therefore lead to better patient selection for ex vivo CD34-selected allo-HCT. The predictive accuracy for both scoring systems is modest, however; and there remains a need for innovative models incorporating new clinical and genomic characteristics to achieve a scoring system with improved accuracy.

Disclosure:

Marta Garcia Recio, MD:

Janssen and Takeda Honorary

Ioannis Politikos, MD:

Funding from Angiocrine Bioscience, Inc.InvestigatorResearch: MerckInvestigatorResearch

Michael Scordo, MD:

Consultancy: McKinsey & CompanyConsultancy and Angiocrine Bioscience, Inc.Consultancy

Gunjan L. Shah, MD:

Funding JanssenInvestigatorResearch and AmgenInvestigatorResearch

Juliet N. Barker, M.B.B.S (Hons), FRACP Doctor:

Funding: Merck & CoInvestigatorResearch, AngiocrineInvestigatorResearch, MerckInvestigatorResearch, GamidaInvestigatorResearch,

Boglarka Gyurkocza, MD:

Actinium Pharmaceuticals Inc.nonemy institution receives research funding from Actinium Pharmaceuticals Inc.

Craig S. Sauter, MD:

Board, Honoraria and Research Funding: Spectrum PharmaceuticalsadvisorAdvisory, NovartisadvisorAdvisory, GenmabadvisorAdvisory, Precision Biosciencesadvisor and research fundsAdvisory

Board and Honoraria: Kite, a Gilead CompanyadvisorAdvisory, Gamida CelladvisorAdvisory, PfizeradvisorAdvisory, GSKadvisorAdvisory Board and Honoraria

Marcel R. M. van den Brink, MD, PhD:

Seres InvestigatorHonoraria, Intellectual Property Rights, Research Funding and Stocks

EveloHonorariaHonoraria

Honoraria: Jazz Pharmaceuticals, Therakos, AmgenHonoraria, Merck & Co. Inc, Magenta Therapeutics

Smart ImmuneInvestigatorStocks, JunoInvestigatorIntellectual Property Rights

DKMSChairmanAdvisory Board

Sergio A. Giralt, MD:

Consultancy: Amgen, Actinuum, Celgene, Johnson&Johnson, JAZZ pharmaceutical, Milteny, Takeda, Novartis, Kite and Spectrum Pharma.

Miguel Perales, MD:

Honoraria from Abbvie, Bellicum, Celgene, Bristol-Myers Squibb, Incyte, Merck, Novartis, Nektar Therapeutics, Omeros, and Takeda. He serves on DSMBs for Cidara Therapeutics, Servier and Medigene, and the scientific advisory boards of MolMed and NexImmune. He has received research support for clinical trials from Incyte, Kite/Gilead and Miltenyi Biotec. He serves in a volunteer capacity as a member of the Board of Directors of American Society for Transplantation and Cellular Therapy (ASTCT) and Be The Match (National Marrow Donor Program, NMDP), as well as on the CIBMTR Cellular Immunotherapy Data Resource (CIDR) Committee

¹University of Patras, Rio, Greece, ²G.Papanicolaou Hospital, Thessaloniki, Greece, ³Hellenic National Centre of Histocompatibility, G. Gennimatas Hospital, Athens, Greece, ⁴University Hospital of Ioannina, Ioannina, Greece

Background: Relapse following allo-HSCT in patients with acute leukaemia remains to date a challenge in clinical practice and is associated with ominous prognosis. Identifying the mechanism leading to relapse will morph our therapeutic armamentarium in accordance with the underlying pathophysiology. Amongst recent studies, HLA Class II downregulation has emerged as a major mechanism of immune evasion after allo-HSCT in patients with AML. However, relapses of patients with ALL after allo-HSCT have not yet been studied in an identical manner. Our goal was to identify the downregulation of HLA-DR in blasts of patients with acute leukaemia after allo-HSCT using flow cytometry.

Methods: For this study, we retrospectively selected patients with a diagnosis of AML, ALL or MPAL who relapsed following allo-HCT for which raw flow cytometry data were available both at a pre-transplantation active disease and at relapse. Blast cells were gated, then analyzed based on their HLA-DR expression and a Mean Fluorescence Intensity was calculated for both timepoints (preMFI & relMFI). Analysis was performed using the FlowJo software (Version 10.5.3, FlowJo LLC). Normalisation of the MFI values was performed using the median HLA-DR MFI of blasts from 31 newly diagnosed acute leukaemias calculated as MFI/median. We defined HLA-DR Downregulation as the reduction of the normalized value at the time of relapse by at least 50% (preMFI-n/relMFI-n < = 0.5). Statistical analysis was performed using Graph Prism.

Results: We analyzed 16 patients (9 male, 7 female) median age of 44 years old (range 32-65) who underwent allo-HSCT for AML (n=12), ALL (n=3) and MPAL (n=1). Four patients received graft from a compatible sibling, 2 from an haploidentical donor and 10 from unrelated donors (7 from 7/8 HLA match, 3 from 8/8 HLA match). At the time of transplantation, 5 patients achieved CR1, 7 achieved CR2 and 4 had refractory disease. The median day of relapse was day 147 (60-405). Median preMFI and preMFI-n values were 10.035 (range 81-14818) and 1.01 (0.008-6.5) respectively, median relMFI and relMFI-n were 7.919 (69-62055) and 0.8 (0.007-6.2). In 8 out 16 paired samples we observed a reduction of the HLA-DR MFI and MFI-n by at least 50% at the time of relapse (median relMFI/preMFI 0.37, range 0.001-0.5). Moreover, HLA-DR downregulation was observed in 2 out of the 3 patients with ALL. There was no correlation between donor-recipient HLA incompatibility and HLA-DR downregulation (p=ns).

Conclusions: HLA-DR Downregulation represents a common mechanism of immune escape in acute leukaemias relapsing after allo-HSCT that accounts to 50% of our patients. We first describe this mechanism to be present in cases of ALL. Identifying this phenomenon in patients using flow cytometry provides valuable information concerning their treatment choices as they will obviously not benefit from donor lymphocyte infusions.

Disclosure: no disclosures

¹University Hospitals Bristol NHS Foundation Trust, Bristol, United Kingdom, ²University of Birmingham, Birmingham, United Kingdom, ³University College London Hospitals NHS Foundation Trust, London, United Kingdom, ⁴King’s College Hospital NHS Foundation Trust, London, United Kingdom, ⁵Queen Elizabeth Hospital Birmingham, Birmingham, United Kingdom, ⁶Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom, ⁷University of Oxford, Oxford, United Kingdom, ⁸NIHR Birmingham Biomedical Research Centre, Birmingham, United Kingdom

Background: Stem cell transplantation (SCT) plays a central role in the management of haematological malignancies and is increasingly utilised in the management of non-malignant disorders. Treatment toxicity and disease relapse remain major causes of treatment failure after both autologous and allogeneic SCT. In contrast to other areas of haemato-oncology where clinical practice is informed by large prospective randomised trials, transplant practice is largely informed by retrospective registry studies and local practice. Very few patients undergoing stem cell transplantation enter prospective randomised trials aimed at improving transplant outcome. Reasoning that major barriers to transplant trial delivery was the twin absence of resource for trial development and research nurse capacity within a large networked population, a 4-year pilot was established in 2017 to create a national transplant trials network in the UK.

Methods: The IMPACT partnership was established in 2017 and £3.4 million was awarded for a 4-year pilot by NHSBT and the charities Anthony Nolan and Leukaemia UK. Funding was awarded with the aim of recruiting at least 500 patients to 9 prospective trials with embedded sequential collection of clinical samples. The IMPACT grant funded a central Hub within a well-established Clinical Trials Unit which was responsible for clinical trial design, set-up, management, and publication of trial results. The Hub was linked with a Trials Network consisting of 10 major transplant centres each staffed by a dedicated IMPACT research nurse chosen through an independent peer review process. 12 additional UK centres were awarded Affiliate status. This effectively created a funded trials network able to recruit to transplant trials in a cohesive manner across a 20 million patient population.

Results: In the 24 months since its establishment the IMPACT network has received 28 proposals for transplant trials - 12 of which have been developed with expert statistical and clinical input from the IMPACT team through national workshops. Rapid feasibility assessments were performed for 10 of these trials. To date 7 trials have been submitted for independent peer review and six have been approved. Key transplant questions addressed include defining the optimal conditioning regimen in acute myeloid leukaemia and acute lymphoblastic leukaemia, studying the role of post-transplant maintenance and donor lymphocyte infusion (DLI) and optimising graft-versus-host disease prophylaxis. 3 trials have been opened with a mean of 12 months to set-up (range 8-18). In its first two years, the IMPACT network has randomised 183 patients to 3 trials. Of note, one trial - Pro-DLI, a randomised trial of DLI administration post-transplant-has fully recruited within 24 months - 8 months ahead of its scheduled target.

Conclusions: Investment in the IMPACT trials hub and network has rapidly transformed set-up and recruitment to prospective randomised trials in SCT within the UK. Key to this success has been its ability to accelerate and coordinate both trials set up and recruitment across a 20 million population. Further investment in such accelerated trial models is required across Europe if patient outcomes after stem cell transplantation are to be improved.

Clinical Trial Registry: N/A

Disclosure: Nothing to declare.

¹Sapporo Hokuyu Hospital, Sapporo, Japan, ² Sapporo Hokuyu Hospital, Sapporo, Japan, ³Aiiku Hospital, Sapporo, Japan, ⁴Hokkaido University, Sapporo, Japan, ⁵Hakodate Municipal Hospital, Hakodate, Japan, ⁶Obihiro Kosei Hospital, Obihiro, Japan, ⁷Asahikawa City Hospital, Asahikawa, Japan, ⁸Sapporo City General Hospital, Sapporo, Japan, ⁹Asahikawa Red Cross Hospital, Asahikawa, Japan, ¹⁰Kushiro Rosai Hospital, Kushiro, Japan, ¹¹Tenshi Hospital, Sapporo, Japan, ¹²Hokkaido Medical Center for Child Health and Rehabilitation, Sapporo, Japan, ¹³Teine Keijinkai Hospital, Sapporo, Japan, ¹⁴Kin-ikyo Chuo Hospital, Sapporo, Japan, ¹⁵Steel Memorial Muroran Hospital, Muroran, Japan, ¹⁶Japanese Red Cross Kitami Hospital, Kitami, Japan, ¹⁷Asahikawa Kosei Hospital, Asahikawa, Japan, ¹⁸Oji General Hospital, Tomakomai, Japan, ¹⁹Tonan Hospital, Sapporo, Japan, ²⁰Higashi Sapporo Hospital, Sapporo, Japan, ²¹National Hospital Organization, Hokkaido Cancer Center, Sapporo, Japan

Background: Recently, the prognosis for patients with acute lymphoblastic leukemia (ALL) has been improved by the introduction of tyrosine kinase inhibitors for Philadelphia chromosome-positive (Ph+) ALL patients and pediatric-inspired protocol for adolescent/young-adult (AYA) patients, and the indication of allogeneic stem cell transplantation (allo-SCT) at first complete remission (CR1) needs to be reassessed. We therefore retrospectively analyzed the impact of allo-SCT for patients with ALL in the era of TKIs and pediatric-inspired protocol for AYA.

Methods: Clinical data for 512 patients who were diagnosed as having ALL between 2007 and 2017 were collected from 21 centers in Hokkaido, Japan.

Results: The median age of the patients was 55 years (range: 15-84 years). Ninety-two of the patients were pediatric (0-14 years), 86 were AYA (15-35 years), 195 were adult (36-65 years) and 148 were elderly patients (66- years). Cytogenetic (G-banding) results were available in 486 patients. Three hundred forty-seven patients had abnormal karyotypes (AK), and 139 patients had normal karyotype (NK). The BCR-ABL fusion gene, including masked Ph+, was positive in 193 patients, and 181 (93.8%) of them were more than 36 years. Abnormalities of complex karyotype were seen in 94 of the patients. After a first remission induction therapy, 418 of 467 (89.5%) evaluable patients achieved complete remission (CR), and BCR-ABL positive patients showed better CR rate than those without BCR-ABL (93.7% vs. 87.4%, P=0.04). At the median follow-up of 1180 days (9-4049 days), overall survival (OS) was superior in patients with NK than those with AK (P=0.01), and BCR-ABL positive patients showed poorer OS than those without BCR-ABL (P=0.01). One hundred fifty-three patients received allo-SCT at CR1. The median age of those patients was 44, and BCR-ABL was positive in 53.9% of those patients. Allo-SCT did not improve overall survival (OS) for patients aged below 35 years. However, allo-SCT significantly improved OS in patients aged over 36 years with or without BCR-ABL (p< 0.01and p=0.03). In BCR-ABL positive patients, allo-SCT improved OS even for patients who achieved molecular remission after first course of chemotherapy (P=0.006). By subgroup analyses of the age groups (pediatric, AYA, adult and elderly), there were no difference of OS between NK and AK. In adult and elderly patients, OS was not different between BCR-ABL positive and negative patients, though in patients over 70 years, BCR-ABL positivity was associated with superior OS (Hazard ratio, 3.2; 95% confidence intervals, 1.04-4.78, P=0.02). In adult or elderly BCR-ABL negative patients, OS of patients with complex karyotype was inferior to those without complex karyotype. Among those patients who achieved CR1 after a first induction therapy, allo-SCT at CR1 was associated with superior OS [HR, 0.40; 95%CI, 0.39- 0.96, P=0.03].

Conclusions: Allo-SCT improved OS for patients with ALL aged over 36 years regardless of BCR-ABL positivity in the era of TKI. Allo-SCT at CR1 should be considered for adult BCR-ABL negative ALL patients, especially in patients who have received non-AYA chemotherapy regimen.

Disclosure: Shuichi Ota received the honoraria of lecture fee from Novartis.

¹Rigshospitalet University Hospital, Copenhagen, Denmark, ²University of Copenhagen, Copenhagen, Denmark

Background: The curative effect of HCT for acute leukaemia is due in part to the donor T cell-mediated graft-versus-leukaemia reaction (GvL). Yet, post-HCT relapse remains a major cause of treatment failure. Donor regulatory T cells expressing the transcription factor Foxp3 (Tregs) have been found to reduce donor T cell-mediated GvHD without compromising GvL.

Methods: We have obtained contrasting results by assessment of the level of Foxp3 mRNA expression by qPCR in pre-harvest donor blood CD4+ T cells in a consecutive series of 45 children and adults, median age 16.7 years, with ALL in 1^st or 2^nd CR who received myeloablative HCT using T-replete bone marrow grafts and post-HCT cyclosporine GvHD prophylaxis. Donor was an HLA identical sibling (N = 11) or an alternative, unrelated (N = 33) or other family (N = 1) donor. Anti-thymocyte globulin (ATG) was given during the pre-HCT conditioning to 28 of 34 patients with an alternative donor.

Results: Post-HCT relapse, defined morphologically, occurred in 17 patients median 363 days post-HCT. By Cox multivariate proportional hazard regression, the effect of donor blood Foxp3 mRNA level on relapse did not meet the proportionality assumption. Proportionality was achieved after dichotomy at the median time of relapse. No effect of donor Foxp3 mRNA level was demonstrated within the first 363 days after HCT. However, after day 363 a higher donor Foxp3 mRNA level was associated with an increased risk of relapse. Thus, seven of eight late relapses occurred in recipients from donors with pre-harvest Foxp3 mRNA level above the median. In contrast, a higher pre-harvest donor CD4+ T cell concentration was associated with a reduced relapse risk. In the multivariate regression analysis, a significant interaction between the pre-harvest donor CD4 T cell concentration and the use of ATG in the conditioning regimen was observed, indicating that the effect associated with donor CD4 T cells was modified by ATG, compatible with the notion that the effect associated with donor CD4 T cell concentration was abrogated in recipients who received conditioning including ATG. However, due to the small sample size it is premature to draw definite conclusions regarding the effect of ATG. Cumulative relapse incidence curves supported the Cox univariate and multivariate regression analysis. Furthermore, we observed a reduction of the probability of surviving in continuous CR associated with higher pre-harvest donor Foxp3 mRNA level and decreased pre-harvest donor CD4 T cell concentration.

Conclusions: A higher Foxp3 mRNA level in CD4+ T cells isolated from pre-harvest donor blood was associated with an increased risk of late relapse in patients with ALL after myeloablative HCT with T-replete bone marrow graft, suggesting that donor Tregs may inhibit GvL. In contrast, a higher pre-transplant donor CD4+ T cell concentration was associated with a reduced relapse risk. The donor CD4 T cell effect was restricted to patients who did not receive ATG during pre-transplant conditioning.

Disclosure: Nothing to declare.

NJ and TF contributed equally to this work.

¹BCN Health Economics & Outcomes Research SL, Barcelona, Spain, ²Jazz Pharmaceuticals Iberia, Barcelona, Spain, ³Universitat de Barcelona, Barcelona, Spain

Background: To review epidemiology, management, use of resources, and costs of acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) via the evaluation of patient records.

Methods: Data were extracted from the Ministry of Health records via the Spanish claims database Minimum Basic Data Set. The database contains patient records compiled in 192 private and 313 public hospitals, covering all Spanish regions, between 1997 and 2015 for AML and between 2008 and 2015 for MDS, according to data availability. All records corresponding to AML and MDS were identified using the International Statistical Classification of Diseases and Related Health Problems version 9 (ICD9) codes: 205.00, 205.01, 205.02, 238.72, 238.73, 238.74, and 238.75. The costs of healthcare usage were calculated based on the mean costs of medical procedures as determined by the Spanish Ministry of Health, which exclude prescription medication.

Results: Overall, records of 39,568 patients with AML and 33,091 with MDS were analysed. In most cases, the AML type was not registered; 9% of the patients were registered as in remission and 1% in relapse at first entry within the study period. When MDS was specified, 18% of the patients were registered with low-grade MDS lesions, 8% with high-grade lesions, and 1% with 5q deletion. Mean age at AML diagnosis was 59 years (SD=21), whereas for MDS it was 78 years (SD=13). Patients were mostly between 70 and 89 years of age and predominantly male. In terms of disease management, of the 102,783 and 64,556 admissions registered for AML and MDS, respectively, 79% and 48% were attributed to haematology services and 58% and 83% of admissions were not scheduled; the median length of hospital stay was 17 days (IQR=26) for AML and 7 days (IQR=9) for MDS. Chemotherapy was the most common procedure performed in patients with AML (44%), followed by platelets transfusion (31%). Transfusion of packed cells (41%) and chest x-ray (20%) were the most common procedures in patients with MDS. There was an increase in bone marrow and hematopoietic stem cell transplants over time in Spain during the study period, from 171 in 1997 (1,494 patients) to 477 in 2015 (3,611 patients). Mean annual direct medical costs were measured throughout the study period and were €66,422,245 for AML and €42,635,313 for MDS; both displayed an increasing tendency over time, with the costs of AML increasing 3.7-fold between 1999 and 2011. Of these, €15,843,982 and €2,705,791 were directly linked to transplants. Mean annual costs per patient were €1,821and €1,288, respectively. In most admissions, (>96%) costs were financed by the Spanish social security system.

Conclusions: This retrospective study identifies patient characteristics, disease management, and health resource use related to AML and MDS treatment in Spain. AML and MDS represent a large burden for the National Spanish Healthcare System, with substantial costs incurred in secondary care settings. A large portion of these costs can be attributed to the increasing number of bone marrow and hematopoietic stem cell transplants.

Disclosure: Teresa Briones is an employee of and holds stock/stock options in Jazz Pharmaceuticals. The other authors have no conflicts of interest to declare.

¹Princess Margaret Cancer Centre, Toronto, Canada, ²University of Toronto, Toronto, Canada

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) can be curative for acute myeloid leukemia (AML). Novel therapies may render patients’ bone marrows profoundly hypocellular and be associated with prolonged post-therapy pancytopenia. In individual patients, bone marrow cellularity (BMC) at pre-transplant assessment (PTP) and post-treatment pancytopenia (leading to classification as CR-incomplete [CRi] as per ELN 2017 criteria) may be a manifestation of disease persistence, and this clinical response to chemotherapy is concerning for treating physicians.

Methods: In the present retrospective study, we examined the impact of BMC and post-treatment blood count recovery on a single-center cohort of 342 patients who underwent HSCT for AML in CR or CRi from January 2013 until December 2018. Data was updated as of November 2019. Median age was 57 years (range 18-73). Disease status at PTP was first complete remission (CR1) in 86% and CR2 or beyond in 56% of patients. Myeloablative conditioning was administered to 31% of patients while 69% received reduced-intensity conditioning. In vivo T-cell depletion was given to 75% of patients. Donors were matched-unrelated, matched-related and haplo-identical related (200, 108 and 34). The median follow-up of survivors was 31 months (10-81).

For BMC, patients were grouped as scoring aplastic (< 10%), hypocellular, normocellular and hypercellular for age (22, 89, 174 and 52 patients respectively; 5 patients had missing data); BMC was assessed by established pathology criteria. For ELN response (ELNr) at PTP, all patients had BM blasts fewer than 5%, and those having neutrophils ≥ 1 and platelets ≥ 100 at PTP were deemed as CR, otherwise CRi (190 and 152 patients respectively). MRC cytogenetic risk as per Grimwade, et al 2010 was favorable=21, intermediate=227, adverse=66 and unknown=28.

Cox proportional hazard model was used to analyze the effects of variables on overall survival (OS) and Fine and Gray’s competing risk regression model was used to examine the effect of variables on cumulative incidence of relapse (CIR).

Results: OS of the whole cohort at 2y was 56.08%, while CIR was 20.31%. CIR for BMC groupings was aplastic 17.28%, hypocellular 22.60%, normocellular 19.63%, hypercellular 21.89%, p not significant (ns), see Figure 1; and for ELNr, CR 18.41%, CRi 22.69%, p ns. OS for BMC was aplastic 63.64%, hypocellular 49.39%, normocellular 56.34%, hypercellular 60.42%, p ns, and for ELNr, CR 56.97%, CRi 55.06%, p ns.

The distribution of MRC cytogenetic risk by BMC was not significantly different (p=0.26) nor was primary induction failure (p=0.759), HCT-CI (p=0.495) or usage of myeloablative conditioning vs reduced-intensity (p=0.988). ELNr CRi was more likely in BMC aplastic and hypocellular, than CR (p< 2.62e-8).

Multivariate analysis confirmed that neither BMC nor attainment of ELNr CR vs CRi had an impact on OS or relapse. Other factors such as age at transplant (p< 0.0001) and chronic GvHD (p=0.0003) influenced OS, while MRC cytogenetic risk (p=0.0009) and chronic GvHD (p=0.0011) affected relapse.

Conclusions: Neither ELN response status (CR vs CRi) nor bone marrow cellularity at pre-transplant assessment influence relapse post-transplant or OS. Hypocellularity and CRi should not be considered negative prognostic factors for post-transplant outcomes of AML.

[Figure 1: Cumulative incidence of relapse of bone marrow cellularity groupings.]

Disclosure: Nothing to declare.

¹Goethe University Frankfurt, Frankfurt, Germany, ²EBMT Paris Study Office, Saint Antoine Hospital, INSERM UMR 938, Sorbonne University, Paris, France, ³American University of Beirut Medical Center, Beirut, Lebanon, ⁴Hopital Saint Antoine, Paris, France, ⁵Bristol Royal Hospital for Children, Bristol, United Kingdom, ⁶University of Milan and ASST Papa Giovanni XXIII, Bergamo, Italy, ⁷University College London Hospital, London, United Kingdom, ⁸Azienda Ospedaliera Universitaria Careggi, Firenze, Italy, ⁹University Hospital Eppendorf, Hamburg, Germany, ¹⁰Royal Marsden Hospital, London, United Kingdom, ¹¹CHU de Lille, LIRIC, INSERM U995, Université de Lille, Lille, France, ¹²Vilnius University Hospital Santaros Klinikos, Vilnius, Lithuania, ¹³Maria Sklodowska-Curie Institute, Gliwice, Poland, ¹⁴Chaim Sheba Medical Center, Tel Hashomer, Israel

Background: Blinatumomab (BLINA) and inotuzumab ozogamicin (INO) have been used for relapsed and refractory B precursor acute lymphoblastic leukemia (ALL) with or without prior allogeneic hematopoietic stem cell transplantation (HSCT). In an international phase II study of 64 patients relapsing after HSCT and treated with blinatumomab, 1-year OS was 36% (Stein AS et al., BBMT 2019), which compared favorably with historical cohorts treated with chemotherapy, donor lymphocyte infusions or a 2^nd HSCT (Spiridonidis A et al., Leukemia 2012). Our retrospective analysis evaluates (i) the impact of BLINA and INO as salvage therapy post-HSCT on OS in a larger patient cohort, (ii) the safety of additional DLI and (iii) the outcome of patients undergoing a 2^nd HSCT.

Methods: We identified 133 adult patients median age 36 (range, 18-68) years with Philadelphia-negative ALL who were treated with either BLINA (n=93, 70%), INO (n=34, 26%) or both (n=6, 4%) within 180 days after their first molecular or hematologic relapse following a first HSCT, performed 2012-2018. Patients were transplanted in CR1 (53%), CR2 (34%) or CR3 (13%) from a matched sibling (32%), matched unrelated donor (55%), other relative (11%) or umbilical cord blood (2%) using myeloablative or reduced-intensity conditioning (77% and 23%, resp.). OS was calculated by Kaplan-Meier analysis. In the multivariate Cox analysis, patient age, CR1 at HSCT, donor type as well as factors associated with a p value < 0.10 in the univariate analysis were included.

Results: Relapse occurred at a median of 7.1 (range, 0.8-80.6) months post-HSCT and immunotherapy was started a median of 15 (range, 0-172) days after relapse. With a median follow-up of 14.8 (range, 7.7-28.3) months after immunotherapy, 1-year OS in all patients was 30.9% (95% CI: 21.7-40.2). In patients treated with either INO or BLINA, probability of 1-year OS was 20.4% (95% CI: 3.6-37.2) and 36.4% (95% CI, 25.2-47.6), resp. (Figure 1, p=0.041). Immunotherapy was applied as monotherapy (n=81, 61%) or associated with chemotherapy (n=52, 39%). Additional cellular therapy included DLI prior to (n=6, 5%) or subsequent to immunotherapy (n=24, 18%) and probability of 2^nd HSCT within one year was 26% (95% CI: 18.8-33.8); these 39 patients had a 1-year OS of 42.4% (95% CI: 23.8-61.1) after 2^nd HSCT. However, neither additional chemotherapy nor DLI or 2^nd HSCT (as time-dependent variable) had a statistically significant effect on OS.

A total of 85 patients died, mostly from leukemia (n=53, 63%) or infection (n=20, 24%). Out of all 40 patients treated with INO, two were reported as dead due to SOS (both received a 2^nd HSCT). In multivariate analysis, female gender (HR 0.45, p=0.001), sibling vs other donors (HR 0.52, p=0.009) and longer time to relapse (HR 0.96, p=0.012) proved to be independently associated with better OS.

Conclusions: In patients relapsing after an allogeneic HSCT, BLINA or INO immunotherapy was associated with 1-year OS rates of 20-36%. Additional DLI or subsequent HSCT seemed to be safe, but did not improve outcome.

[Fig. 1: Overall survival for patients receiving either INO or BLINA after relapse.]

Disclosure:

Gesine Bug: Pfizer: advisory board

Sebastian Giebel: Amgen: honoraria, advisory boards, travel grants; Pfizer: honoraria, advisory baords.

Gazi University, Ankara, Turkey

Background: In 2005, Sorror et al introduced a new prognostic scale for the candidates of allogeneic

hematopoietic stem cell transplantation (allo-HSCT). Since then, several methods were developed to predict the risk of transplant related mortality. This retrospective study was designed to evaluate and compare the efficacy of the conventional and novel prognostic tools including hematopoeitic cell transplant (HCT)-comorbidity index (HCT-CI), HCT-CI/Age and HCT-composite risk (HCT-CR) indices.

Methods: A total of 215 acute leukemia (acute myeloid leukemia / acute lymphoblastic leukemia:

129/86) patients [median age: 37(18-71) years; M/F: 135/80] were included in this study. Medical records of the patients were retrospectively reviewed. Besides European Society for Blood and Marrow Transplantation (EBMT) score, Eastern Cooperative Oncology Group (ECOG) and Karnofsky scales; pre-transplant risk evaluation was performed using HCT-CI, HCT-CI/Age and HCT-CR, as previously described. Disease risk stratification was based on European Leukemia Net guidelines.

Results: Pre-transplant risk scales including EBMT [median score: 3(0-7)], HCT-CI [median score: 1(0-6)], HCT-CI/Age [median score: 1(0-7)] and HCT-CR [Low: 84(39.1%); Intermediate: 11(5.1%); High: 112(52.1%); Very high: 8(3.7%)] were evaluated as well as ECOG [median score: 1(0-4)] and Karnofsky scales [median score: 40(40-100)]. Pre-transplant disease status was first complete remission (CR1) in 150 patients (69.8%), CR2 in 29 patients (13.5%), >CR2 in 1 patient (0.4 %), partial remission in 10 patients (4.7%) and progressive disease in 25 patients (11.6%). A total of 162 HSCTs (75.3%) were related, 44(20.5%) were unrelated and 9(4.2%) were haploidentical transplants. Graft source was peripheral blood in 208 (96.7%) and bone marrow in 7 transplants (3.3%). Conditioning regimen was myeloablative in 158(73.5%) and reduced intensity in 57 patients (26.5%). Patients were divided into two subgroups based on HCT-CR. Group 1 represented low-risk patients, whereas Group 2 was composed of intermediate, high and very-high-risk patients. Sinusoidal obstruction syndrome was found to be more frequent in Group 2 (11.2% vs 2.8%; p=0.021). Prevalence of cytomegalovirus reactivation and acute/chronic graft versus host disease was similar in both groups. At a median 681(4-4774) days of follow-up, patients with low HCT-CR scores represented significantly higher probability of progression free survival (70% vs 53.5%; p=0.016) and overall survival (60% vs 41%;p=0.007) (Figure 1). In univariate analysis, HCT-CI (p=0.002), HCT-CI/Age (p=0.015), HCT-CR (p=0.009), EBMT (p=0.007), ECOG (p< 0.001), Karnofsky (p< 0.001) and C reactive protein levels had significant impact on survival. The significant impact of HCT-CI (p=0.018), HCT-CI/Age (p=0.008) and EBMT (p< 0.001) was confirmed in multivariate analysis.

Conclusions: To date, a variety of factors have been defined to determine allo-HSCT outcome. Both patient and disease related factors may have a role in predicting transplant related morbidity and mortality. This retrospective study underlines the importance of pre-transplant risk evaluation, although more experience is required to identify the better approach in order to improve our foresight in allo-HSCT setting.

[Figure 1. Impact of Risk Groups on Overall Survival]

Disclosure: Nothing to declare.

Mayo Clinic, Rochester, MN, United States

Background: Relapsed acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplant (alloHCT) has a dismal prognosis. The efficacy of venetoclax (VEN) in post alloHCT relapse is understudied. Here we analyze the efficacy and application of VEN in this setting.

Methods: After IRB approval, retrospective analysis was performed for patients with de-novo or secondary AML who received alloHCT, and experienced relapse and were salvaged with VEN+ hypomethylating agent (HMA)/Cytarabine

Results: We identified 12 pts (50% female); median age 57 years (range 30 - 70). Five pts had de-novo AML (ELN adverse risk cytogenetics=2, intermediate risk cytogenetics =3) & 7 pts had secondary AML (ELN adverse risk=5, intermediate risk =2). The donor source was matched unrelated donor (n=7), matched related donors (n=2), haploidentical (n=2) and 1 umbilical cord transplant. 8 pts were in CR1, 3 pts were in CR2, and 1 with persistent residual disease at the time of transplant. Time from transplant to relapse was 196 days (range 77-1142). Time from alloHCT to VEN initiation was 378 days (range 104-1153). Median # of VEN cycles was 2 (1-5). Overall response rate (PR+CR) was 33% (n=4). Median time to CR was 82 days (range 38-125) with median duration of CR of 91 days (1 pt continuing in CR). The Grade 3 or 4 toxicities were infection (n=3) and neutropenia (n=5). Two pts had flare of GVHD on VEN requiring treatment: liver GVHD (n=1); skin, ocular GVHD (n=1). Full molecular information was available for 10 pts at diagnosis and in relapse post-alloHCT: 3 pts acquired TP53 mutations at relapse. Figure 1 outlines evolution of molecular abnormalities in the rest of the cohort, associated venetoclax doses and best responses. None of the pts experienced graft failure after salvage therapy. Estimated median overall survival after VEN was 73 days (Range 2- 403). Nine pts progressed on VEN, 2 pts received subsequent therapy [DLI (n=1), gemtuzumab ozogamicin (n=1)]; 8 of the 9 pts died. Median time from progression on VEN to death was 13 days (IQR 2-43). The most common molecular mutation among responders was TP53. Among 5 pts with TP53 mutation in our cohort; 3 achieved CR. Responders had a better survival compared to non-responders with a median OS 403 days vs 43 days respectively (Log-Rank p=0.011). Responders were naïve to HMA.

Conclusions: VEN-based therapy achieved an ORR of 33% in AML pts with post-transplant relapse, and prolonged survival in responders despite the presence of TP53 mutations. Our observations provides evidence that even in the context of post-transplant relapse with adverse mutations and limited treatment options, VEN- based therapy may be effective in inducing CR and possibly improves survival in responding patients.

Disclosure: Mark Litzow: Astellas: Research Funding; Amgen: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Sanofi: Consultancy; NewLink Genetics: Consultancy; Actinium: Research Funding; Pluristem: Research Funding; Servier: Consultancy

Mrinal Patnaik: Stem Line Pharmaceuticals.: Membership on an entity´s Board of Directors or advisory committees.

First Pavlov State Medical University of St. Petersburg, Saint-Petersburg, Russian Federation

Background: In modern practice, a significant proportion of adult patients with acute lymphoblastic leukemia (ALL) undergo allogeneic bone marrow transplantation (allo- HSCT). The technology of allo- HSCT is improving, therefore it is necessary to evaluate the results and factors affecting the outcome of allo- HSCT in patients with ALL.

Methods: In the study included 191 patients with Ph-negative ALL with median age of 25 years (range, 18-61) who received allo-HSCT undergoing allo-HSCT from HLA-matched sibling (n=38), unrelated (n=123) or haploidentical (n=30) donor in R.M.Gorbacheva Memorial Institute between 2007 and 2019. Median follow-up time was 30 months (range, 2-148 months). By the time of allo-HSCT 41 (21,5%) of patients were in first remission, 80 (41,9%) in second remission, 26 (13,6%) in third or more remission, 44 (23%) in active disease. Reduced intensity conditioning (RIC) was performed in 90 patients (47,1%), myeloablative - in 101 patients (52,9%). Conventional calcineurin-based graft-versus-host disease (GVHD) prophylaxis was used in 90 patients (47,1%). Posttransplant cyclophosphamide(Cy) GVHD prophylaxis was used in 101 patients (52,9%).

Results: 5-years OS and EFS were 44,5% and 37,7%, accordingly, whereas 5-year incidence of relapse was 28,8%. Disease status was the main factor determining the results of transplantation in Ph-negative ALL patients. 5-years OS, EFS and relapse rate (RR) were 73,1%, 56,2%, 34,6%, 2,3% (HR=1,772, 95%Cl 1,46-2,151, p< 0,001) and 68,3%, 45%, 26,9%,2,3% (HR=1,764, 95%Cl 1,469-2,119, p< 0,001), 17,1%, 21,2%, 38,4%,47,7% (HR=2,528, 95%Cl 1,37-4,735, p< 0,001) in 1^st, 2^nd, 3^d and active disease, respectively. RIC was associated with worse survival and increased transplant-related mortality (TRM), 5-years OS, EFS and TRM were 35,3% vs 52% (HR=1,64, 95%Cl 1,113-2,417, p=0,01), 28,8% vs 45% (HR=1,538, 95%Cl 1,069-2,213, p=0,02), 43,4% vs 25% (HR=1,817, 95%Cl 1,073-3,129, p=0,01) for RIC and MAC, respectively. TRM was higher after haplo than after unrelated and HLA-matched sibling allo-HSCT (50% vs 32,5% vs 23,7%, p=0,04). Positive minimal residual disease (MRD) before allo-HSCT determined high RR: 57,1% vs 7,1% (HR=8.119, 95%Cl 2,809-23,21, p< 0,001) for MRD positive and MRD negative. GVHD prophylaxis with posttransplant Cy significantly improved relapse-free and GVHD-free survival (GFRS) and reduced TRM. GFRS in1^st, 2^nd remission was 45,9% vs 10,8% (p< 0,001) patients for Cy and standard GVHD prophylaxis, respectively.

Conclusions: Allo-HSCT in patients with Ph negative ALL is low efficacy. MAC and posttrsnsplant Cy can improve results of Allo-HSCT in patients with Ph negative ALL. Achievement of MRD-negative status is crucial for the outcome thus the studies of bridging strategies are warranted.

Disclosure: Nothing to declare.

Ankara University, Ankara, Turkey

Background: Allo-HSCT is a well-established postremission therapy in adults with AML with certain high-risk features. Two different techniques are currently available for posttransplantation surveillance of disease remission: characterization of posttransplantation chimerism and specific detection of MRD. In this retrospective single-center study, we have attempted to evaluate the impact of both chimerism and flow-cytometric MRD in relapse in a population of patients with AML who received an allo-HSCT.

Methods: A total of 65 patients with AML who achieved complete remission at day+100 after allo-HSCT were included. Chimerism and MRD analysis were performed routinely at 1, 3, 6, 9, 12 months after transplantation at our hematology laboratories. Flow cytometry analyses were done using the flow cytometry system FACSCalibur(BD Biosciences, San Jose, CA). Presence of donor chimerism was determined with microsatellite analysis of short tandem repeats(STR) by PCR(Qiagen Plex Plus Kit(100) PCR Assay, genemapper v3.2). We used our institutional database to evaluate details and characteristics of patients and transplant outcomes.

Results: A total of 194 consecutive patients with AML underwent allo-HSCT at our center between January 2010 and August 2019. For the present study, 65 patients (Female/male: 29/36; median age: 40.5 years(range: 18-67 years)) who had relapsed after Allo-HSCT were evaluated. Median follow up from allo-HSCT was 10.3 months(4-104 months). A total of 36(55.3%) patients underwent allo-HSCT from related donor while 29(44.7%) patients were transplanted from unrelated donors, respectively. The stem cell source was peripheral blood stem cells in 63 patients(96.9%). Fifty-patients received myeloablative conditioning, whereas 15 received a reduced intensity regimen. With regard to MRD status before transplantation, 37 of 65 patients were MRD-negative and 12 patients were MRD-positive and remaining 16 patients had active disease at the time of allo-SCT. After transplantation, 4 of the 37 patients who were initially MRD-negative changed to MRD-positive, whereas 9 of the 12 initially MRD-positive patients achieved at least temporary MRD negativity. Six of the patients with active disease achieved MRD negativity after Allo-HSCT. The relapse rate was 60% at 1 year and higher in the patients with mixed CD3 chimerism(n=20) compared with those with complete chimerism(n=45) at day+90. In addition, at time of relapse among study population only 33 patients had mixed CD3 chimerism. Patients with MRD positivity at day +28 after HCT had the highest incidence of relapse among all prognostic groups analyzed. The median time to hematologic relapse after detection of MRD relapse was median 62 days. Among all patients, 23 patients with MRD relapse and subsequent hematologic relapse also have been detected via a decrease in chimerism. Twenty-one patients had received DLI for MRD-positivity. During follow up 41 deaths were noted.

Conclusions: In light of recent advances in therapeutic options for post-transplantation relapse, improving our understanding of the available relapse prediction tools is becoming increasingly important. Our data presented here show the superiority of flow cytometric MRD over chimerism analysis to predict relapse after allogeneic stem cell transplantation. Therefore, further studies of larger randomized cohorts with high quality data management are required to clarify the role of post-transplantion MRD and chimerism in predicting relapsed in AML.

Disclosure: Nothing to declare.

¹IRCCS San Raffaele Scientific Institute, Milan, Italy, ²Vita-Salute San Raffaele University, Milan, Italy

Background: FLT3-mutated acute myeloid leukemia (AML) has high risk of relapse and still poor outcomes despite allogeneic stem cell transplantation (HSCT). Sorafenib is a multi-kinase inhibitor active in FLT3+ AML both in the pre- and post-HSCT setting.

Methods: from June 2017 to September 2019, 10 patients with advanced FLT3+ AML at transplantation received sorafenib as maintenance therapy after HSCT. Sorafenib was given off-label after provision of an informed signed consent and in the absence of alternative therapeutic options in all patients. Indications were both achievement of complete morphological remission (CR) and hematological engraftment. Exclusion criteria were active GvHD, infections and non-hematological toxicities. Sorafenib administration was prolonged until intolerance or disease progression.

Results: clinical-biological features at baseline and at sorafenib initiation are reported in Figure 1. Median time from HSCT to sorafenib initiation was 121 days (range 75-250). Nine out of 10 patients were still on GvHD prophylaxis. Sorafenib starting dosage ranged from 200 mg QD (6 patients) to 200 mg BID (4 patients) depending on clinical conditions and concomitant medications. Maximal dosage in our series was 200 mg BID in 6 patients and 200 mg QD in 4 patients.

Sorafenib was well tolerated: no hematological toxicity was observed. Most common grade I-IV adverse events (AE) were skin rash (20%), arterial hypertension (10%), sinus bradycardia (10%), diarrhea (10%), hyperbilirubinemia (10%) and peripheral neuropathy (10%). Most common grade III-IV AE was arterial hypertension (10%). Any patient died because of treatment. Four patients had dose reduction and 2 patients had temporary interruption of sorafenib because of AE.

Two patients developed acute GvHD grade 2 overall: no one had previous GvHD; one patient obtained complete remission with steroid treatment, the second completely resolved GvHD after second line therapy (infliximab). Three patients developed chronic GvHD: 2 classic and 1 overlap, maximal overall severity was moderate, 2/3 patients received ≥2 treatment lines.

After a median follow up of 15 months (range 6-36), all patients were alive. Nine patients were still on therapy while 1 patient finally stopped sorafenib after 4 days of administration due to a drug-related grade II sinus bradycardia.

Median duration of maintenance was 360 days (range 4-886). At last bone marrow evaluation, all patients were in CR and all evaluable patients (8/10) obtained MRD negativity.

Conclusions: post-transplantation maintenance with sorafenib proved feasible in FLT3+ AML: we did not reported major toxicity or adverse events. Sorafenib was effective both in preventing relapses and obtaining deep and durable remission.

Disclosure: Nothing to declare.

Pavlov First Saint Petersburg State Medical University, Saint-Petersburg, Russian Federation

Background: Despite advanced effective prophylaxes, PC occur in 40-60% of allo-HSCT recipients, accounting for considerable morbidity and mortality. Transplant procedure influence on development of PC, eg conditioning regimen, immunosuppresive therapy, status of diseases, but complex of these aspects didn’t analyzed in children underwent allo-HSCT. Primary end point:to determine effect of PC in children with AL after allo-HSCT on overall survival (OS). Secondary end points:to describe causes, incidences rates PC and risk factors of such complications following allo-HSCT.

Methods: We included children (n=173) with ALL (n=99) and AML (n=74), median age 11(0-18)y.o. Remission of disease (CR) at allo-HCST was in 108 pts (62%). Related compatible donor-in 16(9%) patients, 80(46%) haploidentical, and 77(45%) matched unrelated donor. Source of HSC was bone marrow (BM) n=138, peripheral blood stem cells (PBSC) n=35 cases. Myeloablative conditioning regimen (MAC) based on busulfan (Bu) (10-16 mg/b.w.) received 105(92%) patients on treosulfan-9(8%) pts., reduced intensity conditioning (RIC) based on melphalan-37(63%) pts, based on Bu(8 mg/b.w.)-22(37%) pts. GVHD prophylaxis was mono-PTCy in 25pts (15%), PTCy±CNI±m-TOR in 68 pts(39%), PTCy±CNI±MMF in 80 pts(46%). Clinical data were analyzed to determine whether the incidence of PC was correlated with risk factors such as age, sex, underlying disease type, transplant type, conditioning regimen, prophylaxis of GVHD using SPSS 23. Kaplan-Meier curves were used to estimate the probability of OS. A p value of < 0.05 was considered statistically significant.

Results: Among 173 pts 121(69%) had PC. Early pulmonary complications (EPC) (before D+100) occurred in 81% (n=98) of pts. Infections EPC observed in 97%(n=95): bacterial complications in 23pts(24%), fungi in 13pts(14%), viruses in 15pts (16%), combined infections: viruses+bacteria in 19pts (20%), viruses+fungi in 7(7%), bacteria+fungi in 11(11%), and combination of viruses, bacteria and fungi in 7(7%) cases. Non-infectious EPC occurred in 39%(n=38)pts: engraftment syndrome 40%(n=15), pulmonary edema 39%(n=15), pulmonary bleeding 3%(n=1), respiratory distress syndrome 13%(n=5). Late pulmonary complications (LPC) (after D+100) occurred in 66%(n=80) pts., infectious LPC observed in 30% (n=24), non-infectious LPC observed in 26%(n=21)pts. According to our data pulmonary changes were seen in 80 pts. In 24(30%) cases were focal, in 17(21%) infiltrative, in 26(33%) interstitial, and 10(13%) cases fibrotic. Three pts developed hydrothorax. 41 pts had no complications. Development of EPC in underlying diseases significantly affects overall survival (p=0.001). 5-OS in patients with early mild complications is 55%vs92.1% without complications. The OS of pts with LPC is 72,7% compared 61.5% of patients who had EPC and LPC (p=0.001). Incidence of PC in remission after МАС is 67,5%(n=77)vs72,9% (n=43) after RIC(p>0,05). Incidence of PC in pts with active underlying disease after MAC-70%(n=31) vs 95%(n=20) after RIC. Type of allo-HSCT, source of transplant, sex, age at the moment of allo-HSCT in CR pts didn’t affect on development of PC(p>0,05).

Conclusions: Incidence of PC was significantly lower in patients receiving allo-HSCT in CR. Intensity of conditioning regimen does not affect the incidence of PC in patients with CR. The use of RICs in relapse increases incidence of PC. Development of early PC in patients after allo-HSCT worsens the prognosis and reduces significantly OS.

Disclosure: Nothing to declare.

¹Peking University People’s Hospital & Peking University, Beijing, China, ²Affiliated Hospital of Soochow University, Soochow, China, ³Nanfang Hospital, Southern Medical University, Guangzhou, China, ⁴First Affiliated Hospital of Soochow University, Soochow, China

Background: Although the need for consolidation chemotherapy after successful remission induction therapy is well established in patients acute myeloid leukemia (AML) in first complete remission (CR1), the value of consolidation chemotherapy before HSCT remains controversial.

Methods: Our study retrospectively compared the effect of the number of pre-transplant consolidation on outcome after HLA-matched sibling stem cell transplantation (MSDT) for AML patients in CR1 in multicenters across China. In addition, our multicenter study also compared the effect of the consolidation therapy pre-transplant between MRD negative patients and MRD positive patients with AML in CR1 who received MSDT.

Results: In our study, we analyzed data of 373 patients with AML in CR1 from three centers across China. All of these 373 patients received MSDT in different centers. With a median follow-up of 969 days, those patients with ≧ 3 cycles of consolidation chemotherapy had higher incidences of LFS (85.6% vs. 67.0%, p< 0.001) and OS (89.2% vs. 78.5%, p=0.007), and better cumulative incidences of relapse rate (10.5% vs. 19.6%, p=0.020) and NRM (4.2% vs. 14.9%, p=0.001). For pre-MRD (minimal residual disease) negative AML patients in CR1 receiving MSDT with ≧ 3 cycles of consolidation chemotherapy had better LFS (85.9% vs. 67.7%, p=0.003) and lower cumulative probabilities of relapse (9.6% vs. 23.3%, p=0.013) than those with ≦ 2 cycles, but the two groups had comparable probabilities of OS (90.0% vs. 80.3%, p=0.051) and NRM (4.9% vs. 10.9%, p=0.127).

Conclusions: In conclusion, our results indicated that AML patients in CR1 who received MSDT might benefit from pre-transplant consolidation chemotherapy.

Disclosure: All authors declare. no competing financial interests.

¹Polish Academy of Sciences, Wroclaw, Poland, ²Lower Silesian Center for Cellular Transplantation with National Bone Marrow Donor Registry, Wroclaw, Poland

Background: Genetical description of AML cases belong now to the standard diagnostic procedure, however it includes mainly chromosome banding assay (CBA) or FISH. In the present study we added information from microarray CNV analysis.

Methods: 127 AML cases (age:21-84, median:59 yrs, 62F/65M) diagnosed in years 2008-2019 (FAB M0=11, M1=37, M2=25, M3=6, M4=27, M5=11, M6=2, secondary=20, primary=107), classified (ELN genetic guidelines) as favourable=17.3%, intermediate=51.2%, unfavourable=31.5%, received treatment according to the PALG guidelines. Genetic work in addition to the CBA, 83 cases or FISH analysis (33 cases) included the microarray analysis of copy number variations (CNV).

Results: 1. The observed survival pattern of the patients followed that seen in the ELN analysis on the dependence of CBA and FISH alterations with survival.

2. CNV number (Catalog Agilent Cancer CGH+SNP 180K (74 patients) or Roche-WG Catalog NimbleGene 12x270K (53 patients)) was worked out using the Partek program (segmentation algorithm with default settings). Numbers of CNVs deletions in the patients varied from 3-104 (median: 22), amplifications from 6-172 (median: 26). Only autosomes were analysed.

3. 197 CNVs> 5 Mbp found in 38 patients could be compared to the picture of CBA in 14 and that of FISH in 24 patients. It appeared that CNV detected were seen either in the CBA or in the FISH in 86 situations. 111 identified CNVs were missed in CBA or FISH among which in 73 instances because the FISH probes are not suited for detection of these particular CNV, the rest 38 CNV which might be seen either in CBA or FISH were missed likely due to the technical reasons. A majority of discrepant results between the FISH or CBA and microarray were likely due to difficulties in proper identification of a part of additional or deleted chromosome seen (6 patients). Altogether, the results of CNV and the standard techniques were the same in 25 cases.

4. In a univariate analysis of the survival risk factors, it was found that better overall survival enjoyed patients:

· under 48 years of age (39 vs 16%, p< 0.001),

· with primary AML (23% vs 15%, p=0.084) compared to secondary AML,

· lacking NPM1 gene mutation (25 vs 11%, p= 0.044),

· who received allogeneic hematopoietic stem cell transplantation (28 vs 19%, p< 0.001),

· having more CNV aberrations in the group with normal karyotype or FISH (50 vs 16%, p=0.008),

· having t(8:21) (RUNX1/RUNXT1, 67 vs 20%, p=0.004). 67% of patients with t(8:21) had an aberrant expression of CD19 (>22% in the blasts) compared to 5% incidence in the patients without translocation (p< 0.001). CNV amplification in the RUNX1 gene was associated with aberrant CD19 expression (40% vs 7%, p= 0.054). In opposite CNV amplifications in the KMT2A gene (9 cases), independently if seen in the FISH assay (3 cases) or not, inversely affected the survival (0 vs 43%, p= 0.032, at the 18 month time point).

Conclusions: CNV analysis offers some information which are clinically valid but missed by CBA or FISH due to the technical reasons.

Supported by RPDS.01.02.01-02-0177/17 “Stawreg” grant.

Clinical Trial Registry: no applicable

Disclosure: The authors declare. that they have no conflict ofinterest.

¹Princess Margaret Cancer Centre, Toronto, Canada, ²University of Toronto, Toronto, Canada

Background: Allogeneic hematopoietic cell transplantation (HCT) may provide cure for acute leukemia where indicated. However, its use is limited by transplant-related complications which lead to increased mortality. This has prompted the development of pre-transplant risk scores such as the Hematopoietic Cell Transplantation-Comorbidity Index (HCT-CI) and the modified European Group for Blood and Marrow Transplantation (mEBMT) score (that examines recipient age, remission status of leukemia, donor-recipient gender combination and donor match). In a large EBMT study Shouval et al (Journal of Clinical Oncology, 2015) developed a machine learning-based prediction model for mortality (EBMT-ADT) that can be used online.

Methods: In the present retrospective study, we examined the impact of the HCT-CI, mEBMT and EBMT-ADT on a single center cohort of 231 patients who underwent allogeneic HCT for acute leukemia from August 2014 until December 2017. Data was updated as of October 2019.

Results: Median age was 56 years (range 19-72). Acute myeloid leukemia (AML) was diagnosed in 200 patients, acute lymphoblastic leukemia (ALL) in 31 patients. Disease status at the time of HCT was first complete remission (CR1) in 81% and CR2 or beyond in 19% of patients. Myeloablative conditioning was administered to 31% of patients while 69% received reduced intensity conditioning. In vivo T-cell depletion was given to 76% of patients. Donors were HLA matched related in 33%, 10/10 matched unrelated in 44%, 9/10 unrelated in 12% and haploidentical in 11% of patients. The median follow up of survivors was 37 months (15-62 months).

For the HCT-CI, patients were grouped as score 0-1, 2-3 and >3 (116, 75 and 40 patients respectively). For the mEBMT score, patients were grouped as 0-2, 3 and 4-5 (76, 121 and 34 patients respectively), while for the EBMT-ADT the respective 100-day mortality was calculated for each patient (excluding haploidentical) and grouped as ≤4.1%, 4.1-11.5% and >11.5%. Patients with higher HCI-CI score demonstrated lower probability for OS (p=0.038, c-statistic 0.57), while neither mEBMT nor EBMT-ADT significantly stratified patients into prognostic groups (p= 0.09, c-statistic 0.54 and p=0.28, c-statistic 0.53 respectively). Multivariable analysis for OS demonstrated that leukemia type (HR 1.82 for ALL, 95% CI 1.16-2.85, p=0.01), HLA matching (HR 0.61 for all fully matched donors, 95% CI 0.41-0.90, p=0.01) and HCT-CI (HR 0.50 for 0-1, 95% CI 0.31-0.81, p=0.004) had significant impact. Based on the HR, a new weighted score was developed for this cohort including leukemia type (AML=0, ALL=1), HLA matching (fully matched=0, mismatch unrelated or haploidentical=1) and HCT-CI (0-1=0, 2-3=1 and ≥4=2). The new score demonstrated improved prognostic capability compared to the other scores (p=0.0004, c-statistic 0.60) (Figure 1).

Conclusions: The mEBMT score and the EBMT-ADT do not adequately prognosticate OS in our cohort of acute leukemia patients undergoing allogeneic HCT. The HCT-CI performs better, however is not a powerful predictor. New approaches are required to develop a pre-transplant risk calculation tool that can be widely applicable to patients from various centers characterized by heterogeneous practices.

[Figure 1: stratification of OS by score based on leukemia subtype, mismatch and HCT-CI”]

Disclosure: Nothing to declare.

¹Pavlov First State Medical University of St. Petersburg, St. Petersburg, Russian Federation, ²Leningrad Regional Clinical Hospital, St. Petersburg, Russian Federation, ³City Hospital No.15, St. Petersburg, Russian Federation, ⁴City Clinical Hospital No.52, Moscow, Russian Federation

Background: The patients (pts) with refractory or relapsed AML (r/rAML) have poor outcomes with 3-year overall survival (OS) no more than 10%. The main goal of therapy in pts with r/rAML is to achieve remission followed by allogeneic hematopoietic stem cell transplantation (alloHSCT). Introduction of targeted drugs is the most promising strategy in the modern therapy of hematological malignancies. Gemtuzumab ozogamicin (GO) is a recombinant, humanized anti-CD33 monoclonal antibody covalently attached to the cytotoxic antitumor antibiotic calicheamicin, which effectiveness depends on more than 75% expression of CD33-glycoprotein on leukemic blasts.

Methods: The study included 39 pts with median age 34 (18-61) years, 12/39, 31% pts were with primary refractory AML (RefAML), 27/39, 69% pts were with relapsed AML (RelAML). The first relapse (Rel1) had 19/27, 70% pts and two or more relapses (Rel>2) - 8/27, 30%. The early relapse (eRel) was observed in 23/27, 85% and late relapse (lRel) were in 4/27, 15% of cases. Based on the ELN 2017 classification, the prognosis was favorable for 10 pts (26%), intermediate for 8 pts (20%), and adverse for 21 pts (54%). All pts treated by the combination of fractionated GO with regiment FLAG (GO-FLAG).

Results: The follow-up period was 27 month. The overall response rate (OR) was 69% (95% CI 54-81): complete remission was achieved in 63%, remission with incomplete hematologic recovery - 37%. The high OR was in pts with extramedullary disease - 85% (95% CI 58-96). AlloHSCT was performed after GO-FLAG in 17 (44%) pts (4- related, 4 - unrelated, 9 - haplo). In two cases alloHSCT was done in active disease. The median time from OR after GO-FLAG to HSCT was 61 (36-148) days. Overall survival and disease-free survival at 1 years (OS1 and DFS1) was 64% (95% CI 48-77) and 63% (95% CI 44-78), respectively. In the allogeneic group the median OS1 was 6 months and in the group without alloHSCT - 2 months. The median DFS1 in pts with and without alloHSCT after GO-FLAG was 4 and 3 months, respectively. The predictive factors associated with a higher response rate were: favorable ELN genetic group (favorable-90% vs intermediate-75% vs adverse-57%, p=0,05); RelAML (RefAML-42% vs RelAML-81%, р=0,02); blast level less than 60% (< 60% level -83% vs >60% level -50%, р=0,03). In all cases we observed neutropenia of 4 gr. and thrombocytopenia 4 gr. Severe hemorrhagic complications (subdural hematoma) was in 1 pts (2,6%). Sepsis was in 13% (95% CI 19-46); fungal infections were in 10% (95% CI 4-24). Hepatotoxicity was presented as a transient increase in ALT level (< 10ULN) in 10% (95% CI 4-24). Sinusoidal obstruction syndrome did not occur in any of the patients. Early mortality was 10% (95% CI 4-24), 4/39 pts. Causes of death were leukemia progression (1 pt), infectious complications (3 pts). No direct association with the GO and death was observed.

Conclusions: GO-FLAG demonstrated the efficacy and acceptable toxicity in pts with r/rAML and can be used as a bridge to alloHSCT.

Disclosure: Nothing to declare.

¹University of Toronto, Toronto, Canada, ²Princess Margaret Cancer Center, Toronto, Canada

Background: Acute Myeloid Leukemia (AML) and Myelodysplastic Syndrome (MDS) with chromosome 3 abnormalities are associated with adverse outcomes. The benefit of allogeneic stem cell transplantation (AlloHCT) in this setting is controversial. This study aims to assess outcomes in this group of patients undergoing AlloHCT.

Methods: This is a single-center retrospective study including 52 patients with AML and MDS with chromosome 3 abnormalities by conventional karyotyping, who received Allo-HCT from October 2000 to August 2019.

Results: The median age of patients was 50 years old (range 19-72). There were 38 patients with AML and 14 patients with MDS. Concurrent presence of monosomy 7 and complex cytogenetics was found in 15 (29%) and 36 (69%) patients respectively. Majority of patients with AML were in first complete remission (CR1) at the time of AlloHCT. Patients with MDS were Intermediate-2 (13%) or High risk (12%) by the International Prognostic Score System (IPSS). Patient and transplant characteristics are summarized in Table 1.

With a median follow up of 4 years, 2-year relapse free survival (RFS) was 33.65% (95% CI, 20.75-47.03), overall survival (OS) was 32.46% (95% CI, 19.63-45.95), cumulative incidence of relapse (CIR) was 48.08% (95% CI, 35.39-65.31), non-relapse mortality (NRM) was 17.57% (95% CI, 10.18-30.33) and graft vs host disease relapse free survival (GFRS) was 22.94% (95% CI 12.17-35.75). Compared to other chromosome 3 abnormalities, patients with monosomy 3 showed the highest risk of relapse and death with 2 year RFS 11.53% (95% CI, 0.86% - 37.51%) and OS 10.26% (95% CI, 0.67% - 35.53%).

On univariate analysis, age greater than 50, monosomy 3, the presence of monosomy 7 and Allo-HCT in AML in CR2 or not in remission, were associated with increased risk of relapse and death. On multivariate analysis, AML in CR1 showed a trend towards improved RFS and OS, however, this was not statistically significant (HR 0.45 (0.20 - 1.04), P= 0.06 and HR 0.45 (0.20 - 1.02), P=0.056 respectively). The presence of monosomy 7 also showed a trend towards increased risk of relapse, however, this was also not statistically significant (HR 2.13 (0.96 - 4.7), p=0.06) (Table 2).

Conclusions: AlloHCT may improve outcomes in select patients with AML/MDS with chromosome 3 abnormalities. Further studies with a larger sample size and the inclusion of molecular mutations are recommended.

Disclosure: Nothing to declare.

King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia

Background: Acute myeloid leukemia (AML) represents 15%-20% of childhood leukemia. Despite substantial progress in the treatment of pediatric AML, approximately 40% of patients die from disease recurrence or treatment-related toxicities. Cytogenetic aberrations and response to the treatment are important prognostic factors in AML. MLL gene rearrangements in AML patients result in unique clinical and molecular genetic characteristics and generally indicate a poorer prognosis. At King Faisal Specialist Hospital and Research Centre (KFSH&RC), Riyadh, we examined the incidence and treatment outcome of MLL-rearranged AML pediatric patients.

Methods: We retrospectively reviewed the clinical data of pediatric patients (age at presentation ≤ 14 years) who were diagnosed and managed at KFSH&RC from January 2005 to December 2016. A total of 201 de novo AML patients´ profiles were reviewed, MLL-rearranged AML patients were identified based on the cytogenetic results. The median follow-up was 104±37.4 Months (95% CI: 30.5-177.6) Months.

Results: A total of 21 out of 201 (10.4%) AML patients found to have MLL gene rearrangements, 52%(11) were female, with a median age at diagnosis of 3.83 years (0.54-13.56). French-American-British (FAB) classification was M5 in17 patients(81%), M4 in 2(9.5%), M7 in 1(4.8%), and M1 in 1(4.8%). The commonest identified partner was t(9,11) in 8 patients(44.4%), followed by t(1,11) and t(11,19) in 4 patients (22.2%) each, t(11,18) and t(6,11) in 1 patient (5.6%) each. Three patients died early within 1 month from diagnosis. 14 out of 18 (77.8%) patients achieved complete remission 1 (CR1) after AML induction chemotherapy with cytarabine/daunorubicin/etoposide (ADE 10+3+5) and cytarabine/daunorubicin/etoposide (ADE 8+3+5).

Three out of 18 (16.6%) required second-line chemotherapy to achieve CR1. One patient failed to achieve CR despite second-line chemotherapy.

The 5-year Overall Survival (OS) for all MLL-rearranged AML patients was 42.9±10.8%. A total of 10 patients treated with chemotherapy alone without hematopoietic cell transplantation HSCT in complete CR1, 5 out of 10 patients have died with progressive disease (PD) /early relapse within an average of 6 months (1-9 months) from CR. 8 patients underwent HSCT in CR1, 4 died with relapse within an average of 13 months (6-18 months), 3 of them failed induction and got second-line chemotherapy before HSCT. All relapsed patients failed to achieve CR2 and died with PD.

Conclusions: Incidence of MLL gene rearrangements in our Centre was 10.4% and associated with poor outcomes. MLL-rearranged AML patients associated with increased risk of early relapse and re-induction failure. CR1 after first-line chemotherapy is an independent prognostic factor.

Disclosure: nothing to declare.

Pavlov First Saint Petersburg State Medical University, Saint-Petersburg, Russian Federation

Background: Results of allogeneic stem cell transplantation (SCT) in primary or secondary refractory leukemia patients remain unfavorable despite the studies of new conditioning regimens. Preclinical studies by Stokes et al. (2016) indicate that substitution of posttransplantation cyclophosphamide with bendamustine (PTbenda) can possibly augment graft-versus-leukemia (GVL) effect in active leukemia mouse model. We conducted a study to evaluate the potential of PTbenda to prevent graft-versus-host disease (GVHD) and potentiate GVL.

Methods: The prospective (NCT02799147) Phase I de-escalation study evaluated 140-100-70 mg/m2 of PTbenda administered on days +3,+4 with or without additional immunosuppressive agents. All patients received myeloablative conditioning with fludarabine and busulfan. Inclusion criteria were diagnosis of acute lymphoblastic (ALL) or acute myeloblastic leukemia (AML), failure of at least to previous induction courses of chemotherapy or immunotherapy, more than 5% of clonal blasts in the bone marrow and good somatic status. The study enrolled 26 patients (pts), enrollment to the 140 mg/m2 group was halted due to stopping rules. Five pts had ALL and 21 - AML. Median blast count was 19% (6-97%). Four pts had matched sibling donor, 15 - matched unrelated donor and 7 - haploidentical, 10 pts had primary refractory and 16 secondary refractory disease. Half of patients received systemic antimicrobial therapy at the time of enrollment. Median age was 27 years (20-56).

Results: All patients but two with ALL disease progression engrafted and 89% had complete remission (CR) after engraftment, while 62% were MRD-negative. The evidence of augmented GVL was supported by the presence of cytokine-release syndrome in 73% of patients: 3 pts had grade 5 CRC, 5 pts - grade 4, 7 - patients grade 3 and 4 pts - grade 1-2. The pattern of CRC was distinct from BiTe and CAR-T one, with fever in all patients, skin vasculitis in 50%, liver function test elevation in 50%, polyserositis in 15% and neurotoxicity in 15%. CRC was associated with significant elevation of serum ferritin (mean 20188 vs 4915 ng/ml, p=0.005). 1-year overall survival was 29%, 40% and 70% in 140, 100 and 70 mg/m2 groups, respectively, but event-free-survival was 29%, 40% and 27% (Figure 1). None of ALL patients had long-lasting CR (0% vs 45%, р< 0.001). In the whole group relapse incidence was 19% and non-relapse mortality (NRM) - 43%. Grade III-IV acute GVHD was observed in 43%, 30% and 33% pts, with significantly higher incidence after haploidentical transplantation (75% vs 22%, p=0.046). Seventy percent of long-term survivors had chronic GVHD with higher incidence after single-agent PTbenda (100% vs 40%, р=0.038).

Conclusions: PTbenda is a promising strategy for refractory AML, but elucidation of the optimal immunosuppressive agent combination is required to control GVHD, CRC and reduce NRM.

[Figure 1. Event-free survival]

Clinical Trial Registry: NCT02799147, clinicaltrials.gov

Disclosure: The authors declare. no conflicts of interest.

¹Paracelsus Medizinische Privatuniversität, Nürnberg, Germany, ²Universitätsklinikum Dresden, Dresden, Germany

Background: NPM1-mutations can be identified in about 30% of adult AML patients (pts). According to ELN 2017 classification they are characterized as favorable or intermediate risk depending on the coexistence of FLT3 mutations. For pts with a favorable risk profile an allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission (CR) is not recommended, but can be an option for the intermediate risk group, depending on risk factors like comorbidity. Approximately 30% of NPM1-mutated AML pts will relapse after chemotherapy. Because NPM1 mutations are stable, and persisting or increasing levels are a strong predictor of relapse, monitoring of minimal residual disease (MRD) by quantitative PCR (qPCR) is recommended. With this strategy relapse can be detected earlier with lower leukemia burden. HSCT in molecular relapse could avoid possible complications of reinduction chemotherapy, but there are no data for this strategy. In 2014 we decided to start donor search immediately after molecular relapse and proceed to HSCT without reinduction chemotherapy. Here we report our experience with the first 6 pts treated with this strategy.

Methods: Between January 2014 and December 2018 28 patients under the age of 70 years, who were fit for intensive chemotherapy were diagnosed with NPM1-mutated AML. All pts received induction with DA 3+7 followed by consolidation with high-dose AraC in 15 pts. In 10 pts HSCT as consolidation treatment was performed. 3 pts had induction failure. MRD was monitored at least every 3 months (mos) after end of consolidation therapy by qPCR in bone marrow or peripheral blood in all pts in hematological CR. Relapse was defined as an increase of MRD over a cut-off of 1% NPM1/ABL1. The conditioning regimen consisted of Treosulfan (Treo, 30g/m²) and Fludarabin (Flu, 120mg/m²). In pts with hematological relapse at the time of HSCT Melphalan (Mel, 100mg/m²) before Treo/Flu was added to induce aplasia. Immunosuppression consisted of ATG and Ciclosporin in combination with MTX or MMF.

Results: 25/28 pts achieved hematological CR after induction therapy, 24/25 pts showed molecular CR after the end of consolidation treatment. 10 pts (40%) relapsed. 4/10 pts developed an overt hematological relapse and are not part of this analysis. In 6 pts molecular relapse was detected. 5/6 pts relapsed after complete molecular remission, 1 pt relapsed after MRD positive remission. The median time to molecular relapse was 8 (7-42) mos after diagnosis. Median time from first positive MRD to HSCT was 2 (2-4) mo. 3/6 pts received conditioning with Treo/Flu only. 3/6 pts had hematological relapse at time of HSCT and received Treo/Flu after induction of aplasia with Mel. All pts reached complete hematological and molecular remission after HSCT. After a median follow-up of 15 (8-47) mos all pts are in ongoing CR. In all but one pt the remission free survival is longer than after primary treatment.

Conclusions: Although the number of pts is small and the follow-up short, this analysis shows the efficacy and feasibility of early allogeneic HSCT in molecular relapse for NPM positive AML pts and should be confirmed in a greater number of pts.

Disclosure: No disclosure

IRCCS San Raffaele Scientific Institute, Milan, Italy

Background: consolidation of complete remission (CR) with autologous stem cell transplantation (ASCT) is an option for patients (pts) with acute myeloid leukemia (AML), in particular for those with a favourable genetic risk (ELN 2017). Most conditioning regimens for ASCT contain at least one alkylating agent, usually busulfan, cyclophosphamide or melphalan. Up to now, no regimen has proved preferable in terms of toxicities and improvement of event free survival (EFS). Treosulfan is an alkylating agent which demonstrated to achieve maximum disease control with minimal toxicity in combination with fludarabine prior to allogeneic SCT. We designed and tested a new treosulfan-based conditioning regimen (FLAT) prior to ASCT in AML pts in first complete remissione (CR1). Preliminary data on the feasibility and efficacy of the FLAT regimen are here presented.

Methods: period 7/2006-7/2019, 30 pts with AML in CR1, median age 68 y (18-76), 14 pts £ 65 y (group A: median 49 y, 19-65), 16 pts > 65 y (group B: median 73 y, 68-77). Cytogenetics: favourable 1, intermediate 26 (normal karytotype 25), complex 1, not evaluable 2. Molecular (21 pts): CBFB-MYH11 1, RUNX1-RUNX1T1 1, NPM1mut alone 5, CEBPAmut alone 4, FLT3ITD/NPM1mut 5 (FLT3ITD low ratio 3, unknown ratio 2), negative 5. Prognostic risk (ELN 2017): favourable 14, intermediate 7, adverse 1, not evaluable 8. At ASCT all pts were in CR1 after a median number of 2 chemo cycles (2-4). FLAT regimen: treosulfan 10 gr/sqm for 3 days, fludarabine 30 mg/sqm for 5 days, cytarabine 2 gr/sqm for 5 days, PEG filgrastim 1 vial s.c. after autoSCT (27 pts). Graft: PBSC, median CD34+ 5x10⁶/kg of BW (3.3-8.5). Time from CR1 to autoSCT: median 99 days (44-266).

Results: at day +100 after ASCT 29 pts were alive, 24 in CR, 5 relapsed. One 75-yo patient died for invasive fungal infection at day +31 (she was still in G4 pancytopenia). Median time to hematopoietic recovery: neutrophils (> 500/mcl) day +11 (8-38), platelets (> 20.000/mcl) day +20 (13-103). Neutrophils recovery in 3 pts who did not receive any growth factor was slower (day +26, 33, 38). Extra-hematologic toxicities (CTCAE v4.0): median grade 1 (0-4). Median EFS from ASCT was 1123 days (31-4808), for group A 1123 days (84-4808), for group B 653 days (31-4789); projected 3y EFS from ASCT was 51.2%, for group A 57.1%, and group B 47.8% (p=ns). At last update 15 pts (50%) are alive, 13 in CR1, 2 in second CR, with a median follow up of 1561 days (146-4810). Overall non-relapse mortality was 3%.

Conclusions: consolidation of AML in CR1 with the new myeloablative FLAT regimen and ASCT was feasibile and well tolerated, even in patients above 65 years of age. Around 50% of pts, regardless of age, mostly with favourable or intermediate genetic risk, obtained prolonged survival without relapse.

[EFS from ASCT]

Disclosure: nothihg to declare.

¹National Taiwan University, Taipei City, Taiwan, Republic of China, ²National Taiwan University Hospital, Taipei City, Taiwan, Republic of China, ³Hualien Tzu Chi Hospital, Hualien City, Taiwan, Republic of China, ⁴National Taiwan University Cancer Center, Taipei City, Taiwan, Republic of China

Background: Introduction of tyrosine kinase inhibitor (TKI) for the treatment of Philadelphia chromosome‐positive acute lymphoblastic leukemia (Ph+ ALL) has dramatically improved the survival outcomes. However, TKI therapy for Ph+ ALL has yielded controversial results evaluating the efficacy of post-hematopoietic stem cell transplantation (HSCT). The CIBMTR analyzed 197 patients with Ph+ ALL undergoing allo-HCT in first complete remission, 43 of whom received post-transplant therapy with TKIs. There was no difference in the 3-year cumulative incidence of relapse. In contrast, an EBMT study of 473 patients showed that post-transplant TKI was associated with a lower relapse rate and better overall survival. Recently, Akahoshi et al reported that TKI prophylaxis was not associated with a decreased risk of relapse or superior overall survival in the whole cohort. Therefore, we conducted a retrospective study of Ph+ ALL patients at our hospital to evaluate whether TKI prophylaxis after allogenic HSCT would reduce relapse and improve overall survival.

Methods: The Institutional Research Board approved the retrospective study. We identified 68 patients over 14 years of age with Ph+ ALL who received allo-HSCT from 1993 to 2001 (n=3) and from 2002 to 2019 (n=65) at National Taiwan University Hospital. Univariate and multivariate analysis was performed using Cox proportional hazard regression model.

Results: Before allo-HSCT, 8 of 68 patients (12%) didn’t receive any TKI treatments, whereas the remaining 60 patients received imatinib (24%), dasatinib (54%), nilotinib (6%), and ponatinib (4%). After allo-HSCT, 28 patients (41%) didn’t receive TKI treatments, and 40 patients (59%) received TKI treatment, including 2 patients (3%) with flank relapse, 17 patients (25%) with TKI prophylaxis and 21 patients (31%) with pre-emptive treatment because of positive-minimal residual disease (MRD) detected by quantitative PCR. The median time from HSCT to TKI treatment was 52 days (range, 21-542 days). Imatinib (15%), dasatinib (38%), nilotinib (4%), and ponatinib (2%) were given as TKI treatment. The median duration of TKI treatment of the patients was 453 days (range, 7-1775 days). Multivariate analysis identified advanced disease status before HSCT (primary induction failure, active disease) to be a risk factor for overall survival (OS) (HR=7.156; P=0.0002), disease-free survival (DFS) (HR=4.829; P=0.0113), and cumulative incidence of relapse (CIR) (HR=5.3; P=0.0188). Importantly, in the post-transplant period, the multivariate analysis identified TKI administration to be a significant factor for OS (HR=0.30; P=0.0014), DFS (HR=0.25; P<0.001), and CIR (HR=0.343; P=0.0039). Molecular relapse detected by quantitative PCR after HSCT was correlated with increased risk of hematological relapse (CIR, HR=8.158; P=0.005), but not associated with a worse DFS (HR=1.042; P=0.8827). This result could be explained by the fact that 21 of the 32 patients with molecular relapse received TKI treatment and 9 of them returned to negative MRD in a later follow-up assessment.

Conclusions: Despite the limitation of small sample size and the potential bias of patient selection by the physician, our study showed TKI treatment after allogeneic HSCT would reduce relapse and improve overall survival, indicating the potential benefit of TKI treatment in the post-transplant setting.

Disclosure: Nothing to declare.

Yonsei University, Seoul, Korea, Republic of

Background: Acute myeloid leukemia (AML) has been recognized as a clinically and genetically heterogeneous disease entity. Cytogenetic abnormalities that are associated with the prognosis of AML have been identified. However, as there are limitations for patients in the cytogenetic intermediate-risk group, more precise risk stratification systems based on genetic status have been proposed especially in nest-generation sequencing (NGS) era. In this study, we evaluated the usefulness of the European Leukemia Network (ELN) 2017 risk stratification system and transplant outcomes in the cytogenetic intermediate-risk group.

Methods: We performed a retrospective analysis of a total of 143 patients who diagnosed with cytogenetic intermediate-risk AML and received intensive standard ‘7+3’ chemotherapy for remission induction from 2012 to 2018 at Yonsei university Severance hospital in Korea.

Results: According to the ELN 2017 risk stratification system, 30 (21.0%), 80 (55.9%), and 33 (23.1%) patients were allocated to the molecular favorable, intermediate, and adverse risk group. The 5-year overall survival (OS) rate was 78.5% in molecular favorable group, 51.2% in molecular intermediate group, and 33.1% in molecular adverse group (P = 0.010) The 3-year progression free survival (PFS) rate in molecular favorable group were also significantly higher than those in intermediate and adverse group (85.3% vs 56.0% and 49.1%, P = 0.021). The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) was evaluated in 124 patients who achieved complete remission. Among them, 71 (57.3%) patients received allogeneic HSCT as post-remission therapy, and the remaining 53 (42.7%) patients received consolidation chemotherapies only. Despite the higher proportion of patients receiving more than 2 cycle of induction chemotherapy (21.1% vs 5.7%, P = 0.016), the 3-year PFS was significantly higher in the transplant group than non-transplant group (71.2% vs 50.3%, P = 0.013). In molecular risk subgroup analysis, molecular favorable-risk subgroup showed about 80% PFS in both groups and transplantation did not show superiority (P = 0.853). In molecular intermediate-risk group, allogeneic HSCT resulted a longer PFS (P = 0.003) than chemotherapy as a post-remission treatment. For patients with molecular adverse-risk, poor prognosis could not be overcome neither chemotherapy nor transplantation (P = 0.198).

Conclusions: The molecular risk stratification of the ELN 2017 successfully distinguished long term prognosis in cytogenetic intermediate-risk AML patients and validated in our center. Because molecular evaluation using NGS technique recently became one of standard pre-treatment evaluation for AML patients in Korea, clinical benefit of HSCT should be carefully and precisely evaluated for cytogenetic intermediate-risk patients according to the molecular risk stratification. Furthermore, more effective post-remission treatment strategy should be determined especially for cytogenetic intermediate- and molecular poor-risk AML patients.

Clinical Trial Registry: This study was approved by the institutional review board of Severance Hospital (4-2010-0669, NCT 02344953).

Disclosure: There is no funding to declare.

Institute of Haematology and Blood Transfusion, Prague, Czech Republic

Background: The aim was to confirm our previous experience with prognostic relevance of WT1-MRD status before allo-SCT in AML patients in complete remission. Another aspect was to assess the significance of WT1-MRD monitoring in these patients after allo-SCT.

Methods: The expression of WT1 gene was measured by real-time polymerase chain reaction in peripheral blood according the European Leukemia Net recommendations. Between 2005-2019, we have analyzed 147 consecutive AML pts with high WT1 expression at diagnosis, transplanted in CR1 or CR2. Median age was 46 years (range; 21-66), 76 men, 21 good risk, intermediate risk 91, high risk 35. A total of 116 pts were transplanted in CR1 and 31 pts in CR2. In 128 pts PBPC were used, in 19 pts bone marrow. The donors were identical siblings in 30 pts, 9 haploidentical, matched unrelated donors in 73 pts and mismatched UDs in 35 pts. Conditioning was myeloablative in 117 pts, RIC in 30 pts. At the time of allo-SCT 107 pts were WT1-negative (WT1< 50 copies) and 40 pts were WT1-positive.

Results: Median follow-up was 21 months. Estimated 5-years OS and EFS was signifcantly better in WT1 neg cohort (65% and 57% vs 37% and 25% resp, p= 0,0003 and < 0,0001), as well as 5-years RI was significantly lower in WT1 neg group (25% vs 60%, p< 0,0001). 5-years NRM was not significantly different (24% and 27%). Multivariate analysis revealed WT1-MRD positivity and aGVHD grade 3-4 as a significantly negative prognostic factors for OS. Overall 50 pts developed WT1-MRD positivity in post-transplant period, in forty cases the therapeutical intervention was done. Haematological relapse occurred in 42 pts, in all relapsed patients where WT1-MRD was monitored (38 pts) we detected the positivity, in median of 28 days (0-485) before haematological relapse. 3-years OS in pts with molecular relapse only (12 pts) was 56% vs 74% in non-relapsed group (p=ns).

Conclusions: The results of the analysis confirmed our previous experience that WT1 status before allo-SCT is a strong prognostic factor for both OS and relapse risk. Our experience suggests that this marker is also useful for monitoring MRD after allo-SCT. Well-defined clinical studies will be needed to assess the importance of therapeutic intervention based on WT1-MRD positivity.

Disclosure: nothing to declare.

First Pavlov State Medical University of St. Petersburg, Saint-Petersburg, Russian Federation

Background: Widespread use of targeted therapy with tyrosine kinase inhibitors (TKIs) in combination with allogeneic hematopoietic stem cell transplantation (allo-HSCT) has dramatically improved therapy results in the majority of Ph-positive acute lymphoblastic leukemia (ALL) patients, so nowadays their survival may be comparable with Ph-negative ALL patients in most cases. Nevertheless, relapses remain a major cause of treatment failure even after allo-HSCT that lead to dismal prognosis. One of the possible strategies to prevent relapse includes posttransplant TKIs maintenance, but the data about its application regimens is still controversial. The aim of our study was posttransplant TKIs impact evaluation on outcomes of alloHSCT in Ph-positive ALL recipients.

Methods: This study analyses the data in retrospective cohort of 96 Ph-positive ALL patients with median age of 30 years (range, 18-57) undergoing allo-HSCT from HLA-matched sibling (n=24), haploidentical (n=12) or unrelated donor (n=60) in R.M.Gorbacheva Memorial Institute between 2007 and 2019. Median follow-up time was 24,8 months (range, 1-98 months). At the time of allo-HSCT 54 (56%) of patients were in first remission, 16 (10%) in second remission, 10 (16%) in third or subsequent remission, 16 (10%) in active disease (relapse/resistance/progression). 88 (92%) patients received 1^st, 2^nd or 3^rd generation TKI prior to allo-HSCT. 36 (38%) patients were MRD-negative before allo-HSCT, while 39 (40%) had MRD-positive status, measured by PCR analysis. In posttransplant period 60 (63%) patients received TKIs (imatinib or dasatinib). The goal of posttransplant TKIs administration was prophylactic in 43 (72%) patients, preemptive in 8 (13%) and relapse treatment in 9 (15%). Median time of TKIs administration was 60 (range 30-125) days after allo-HSCT. Landmark analysis was used for comparison with patients without TKIs. Non-engrafted patients were excluded from analysis.

Results: 5-year OS and EFS were 59,4% and 45,8%, accordingly, whereas 5-year incidence of relapse was 35,4%. Comparing patients, who received posttransplant TKIs as prophylaxis with those, who did not receive prophylactic TKIs, we observed that 5-year EFS in 1^st group was 63,3% vs 29% in 2^nd (p< 0,001). 5-year incidence of relapse in 1^st and 2^nd groups were 51,6% vs.28,6%, accordingly (p< 0,001). We also estimated, that TKIs generation after allo-HSCT did not influence the results.

Conclusions: In our study 5-year EFS was twice better in patients, who received TKIs after allo-HSCT as prophylaxis, regardless the generation. Moreover, 5-year incidence of relapse was more than 20% lower in this group of patients. Thus, we can suggest that in order to reduce risk of relapse, it is preferable to prescribe TKIs no later than 60 days after allo-HSCT, before measurable residual disease appear, if there are no other factors that limit TKIs administration (toxicity of TKIs, poor graft function, etc.).

Disclosure: Nothing to declare.

Ankara University, Ankara, Turkey

Background: Anti-thymocyte globulin(ATG) is a very effective form of in vivo T-cell depletion and has been extensively used for GVHD prevention. However, ATG can potentially eliminate alloreactive donor T cells and reduce the graft-versus-leukemia(GVL) effect and increased disease relapse and reduced overall survival(OS). Herein, we aimed to investigate the impact of ATG on the outcomes of patients with AML stratified by flow cytometric MRD status who underwent Allo-HSCT from unrelated donor (UD).

Methods: This was a retrospective single center analysis using the data set of our institutional database. Eligibility criteria for this analysis included 75 adult patients with AML who underwent allo‐HSCT from either a HLA 10/10matched(n=34) or 9/10mismatched(n=41) UD, between October2012 and June2019. All recipients received peripheral blood stem cells grafts. Recipients of UD Allo-HSCT were routinely given rabbit Jurkat cell line-reactive ATG(ATG Fresenius®) in doses of 10mg/kg/day IV on days -3, -2, -1. Flow cytometry analyses were done using the flow cytometry system FACSCalibur(BD Biosciences, San Jose, CA) and sensitivity theresholds was 10^-6. All analyses were done separately in patients achieving or not MRD negativity before transplant.

Results: A total of 75 consecutive patients with AML who underwent allo-HSCT from an UD were evaluated. Median age was 48 years(range:19-71) and 40(53.3%) were females. Median follow up from allo-HSCT was 9.8 months(4-80.9 months). There were 43 MRD^-and 11 MRD⁺patients and 21 patients who were transplanted in the setting of active disease also included in this analysis. Fifty-five(73.3%) patients received myeloablative conditioning(MAC) and 20(26.7%) reduced-intensity conditioning(RIC) regimens. The most common MAC and RIC regimens were busulfan/cyclophosphamide(BuCy,60%) and busulfan/fludarabine(BuFlu,25.3%), respectively. The common GVHD prophylaxis were cylosporinA(CSA) and methotrexate(Mtx) in 64(85.3%) of the patients. Eight patients out of 21 patients with active disease underwent to allo-HSCT after FLAMSA-based high-dose sequential conditioning regimen. The use of ATG was associated with a lower incidence of chronic GVHD(18.7%). We investigated the influence of ATG on transplant outcomes separately in MRD^-, MRD⁺and active disease cohorts. As expected, lowest incidence of relapse was observed in MRD^- groups(MRD^-; 23.3%(10/43) vs MRD⁺; 45.5%(5/11); p=0.168). MRD status at the time of allo-HSCT impact the leukemia free survival(LFS) significantly; MRD^-(not reached) or MRD⁺(median 34.8(95% CI, 14.4-55.1)) or active disease(median 8.9 months(95% CI, 5.5-12.3))(p=0.021). In the group of MRD⁺patients, the OS was 21.6 months(95 % CI, 0.60-31.5) with 1- and 3- year OS rates of 72.7 ± 0.8 % and 31.2 ± 1.7 %, respectively(p=0.117). For the MRD^-group, median OS after allo-HSCT was not reached versus 8 months in the active disease group(p=0.053). No outcome differences were found between MAC and RIC regimens. In addition, we did not find any association between type of HLA matched, relapse or GVHD incidences. Infection was the most common cause of death in the both groups.

Conclusions: Based on this single center study, the use of ATG was associated with a lower incidence of chronic GVHD. Most importantly, ATG could increase the risk of disease relapse or mortality in patients with pre-transplant MRD⁺and active diseases. However, further prospective, randomized studies on a large number of patients are warranted to clarify these findings.

Disclosure: Nothing to declare.

Hebei Yanda Lu Daopei Hospital, Sanhe, China

Background: Acute leukemia with MLL-AF6 fusion gene positive is the adverse factor of prognosis. The purpose of this study is to evaluate the outcome of allo-HSCT in the treatment of MLL-AF6 fusion gene positive acute leukemia.

Methods: The clinical characteristics and prognosis of 32patients with MLL-AF6 fusion gene positive acute leukemia from May 2012 to September 2019 were retrospectively analyzed. Twenty four patients received allogeneic hematopoietic stem cell transplantation, including 21patients with AML and 3 patients with T-ALL. 13 were males and 11 were females. Median age was 22(4-48) years old. The disease status before transplantation was CR1 (n = 10) CR2 (n = 2), NR (n = 12). The median time from diagnosis to HSCT was 24(4-352) months.

Patients underwent matched sibling donors HSCT (MSD-HSCT)(n=4), haploidentical HSCT (Haplo-HSCT)(n=20). The conditioning regimens are based on BU/Cy (n=20) and TBI/Cy (n=4). GVHD prophylaxis consisted of ATG, CSA, MMF and MTX.

Results: The number of mononuclear, CD34+ and CD3+ cells was (9.3±1.42)×10⁸/kg, (4.1±1.1)×10⁶/kg, and (1.6±0.5)×10⁸/kg, respectively. White blood cells were successfully engraftment in 22 patients and the median time of ANC≥0.5×10⁹/L was day 12(9-16). One patient failed to engraftment and one patient was not engraftment. Median time of platelet≥20×10⁹/L was day 13(9-30) except 2 case. One patient failed to engraftment and one patient was not engraftment. DLI infusion was used to prevent recurrence in most patients after transplantation. The cumulative incidence of grade II - IV aGVHD was 41%, and the incidence of cGVHD was19%. Five-year overall survival(OS) rate and disease free survival(DFS) were 52.2% and 52% respectively. The five-year OS of allogeneic hematopoietic stem cell transplantation in CR1-2 and NR was 83.3% and 25%, respectively (P = 0.001). The mortality rate was 17% within 100 days. Transplant related mortality: 37%. Ten patients died, the causes of death were infection (n=2), IV aGVHD(n=3), and relapse(n=5). Eight patients received chemotherapy, all of them were AML patients, 5 males and 3 females, the median age was 26.5 (3-52) years old; eight AML patients were not relieved after the first chemotherapy, 3 patients only achieved remission after 2-4 chemotherapy, 5 patients were not relieved after multiple chemotherapy, 6 patients died, the cause of death: the primary disease was not relieved or relapsed; the overall survival was 2 cases. The OS rate was 52.2% in the transplantation group and 25% in the chemotherapy group (P = 0.237).

Conclusions: This study shows that MLL-AF6 acute leukemia has poor response to conventional chemotherapy and poorprognosis, so it is necessary to carry out allogeneic hematopoietic stem cell transplantation in remission state as early as possible.

Disclosure: Nothing to declare.

¹Dong-A University, Busan, Korea, Republic of, ²Sunkyunkwan University, Seoul, Korea, Republic of, ³University of Ulsan, Seoul, Korea, Republic of, ⁴Seoul National University, Seoul, Korea, Republic of, ⁵Seoul National University Hospital, Seoul, Korea, Republic of, ⁶National Cancer Center of Korea, Goyang, Korea, Republic of, ⁷Soonchunhyang University, Soonchunhyang University Hospital,, Seoul, Korea, Republic of, ⁸Kosin University Gospel Hospital, Busan, Korea, Republic of, ⁹Chonnam National University, Hwasun, Korea, Republic of, ¹⁰Chonbuk National University, Jeonju, Korea, Republic of, ¹¹Seoul National University Bundang Hospital, Seoul, Korea, Republic of, ¹²Ulsan University Hospital, Ulsan, Korea, Republic of

Background: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare aggressive hematologic neoplasm which originates from the professional type I interferon-producing cells or plasmacytoid monocytes. The prerequisite for its diagnosis is the CD4+ and CD 56+ co-expression without common lymphoid or myeloid lineage markers. Recently, targeted therapy with Tagraxofusp (SL-401), an IL-3 fusion protein which binds to CD123, has proved its efficacy with an overall response rate (ORR) of 90% in 32 untreated and 67% in 15 previously treated BPDCN patients. Although several retrospective and small case series has been published so far, there is few population-based study on BPDCN classified after 2008 WHO classification in Asian populati.

Methods: Data of 35 patients who were diagnosed with BPDCN from April, 2002 to February 2019 in 11 centers of South Korea were retrospectively collected and analyzed. Pathologic slides were reviewed in the central lab by the 2 pathologic experts and were finally confirmed for diagnosis. Overall survival was defined by the period from the date of the initial diagnosis to death by any cause or follow-up loss.

Results: The median age of the patients was 54.5 years (range, 17 - 84 years) with a male preponderance of 71.4% (25 of 35). 5 patients were preceded with hematologic malignancies. The most common initial presenting site was skin followed by lymph nodes, bone marrow, spleen, and liver. 32 of the included patients proceed to treatment with acute lymphoblastic leukemia (ALL)-like regimen (19 patients), acute myeloid leukemia (AML)-like regimen (5 patients) and lymphoma-like regimen (8 patients). Baseline characteristics of age ≥ 65 years, liver involvement and induction chemotherapy with lymphoma-like regimens expected worse prognosis in both univariate and multivariate analysis. Among the 32 patients who received induction chemotherapy, 11 cases proceeded to allogenic stem cell transplantation (SCT) and 3 received autologous SCT. With a median follow-up of 16.60 months (range, 0.53-79.73 months), patients who had been treated with leukemia-like induction regimen compared with lymphoma-like induction regimen (39.30 vs. 6.33 months, P=0.005) and allogeneic SCT compared with autologous SCT (54.13 vs. 7.70 months, P=0.015) showed markedly prolonged overall survival.

Conclusions: Induction treatment with leukemia-like regimen and proceeding to allogeneic stem cell transplantation can prolong overall survival in Asian patients with BPDCN.

Disclosure: There is nothing to declare.

Yonsei University, Wonju, Korea, Republic of

Background: Anti-apoptotic proteins like Bcl-2, Bcl-Xl, or Mcl-1 play an important role in tumor cell survival and has been considered attractive drug targets. Especially, Bcl-2 selective inhibitor, venetoclax, has been showing significant effects on hematologic malignancies, but lower sensitivity and resistance gain have to be overcome to achieve durable response in acute myeloid leukemia (AML). Because intracellular pH is one of important modulators for Bcl-2 or Bax via deamidation process, in this study, we examined whether the cotreatment of Na/H exchanger 1 (NHE1) inhibitor, HMA [5-(N, N-hexamethylene)-amiloride] can overcome the resistance to venetoclax in AML cell lines.

Methods: Based on the preliminary experiments, venetoclax were treated to both venetoclax sensitive cell lines (MOLM13, MV4-11, and RS4-11) and venetoclax resistant THP1 cell line (THP1 and U937) with various concentration, and HMA was co-treated with 10 uM. Apoptotic cells were measured after 24 hr treated with each agent or combination. Apoptosis was analyzed using Annexin-V assay.

Results: As expected, venetoclax monotherapy induced concentration-dependent apoptosis in venetoclax sensitive MOLM13, MV4-11, and RS4-11 cells. For these cell lines, cotreatment of HMA to venetoclax synergistically potentiated apoptosis, and relatively lower concentrations of both drugs could induce almost complete apoptosis. For venetoclax resistant THP-1 and U937 cells, venetoclax could not induce sufficient apoptosis even with higher concentration. However, the combination treatment of HMA overcome venetoclax resistance, and induced apoptosis with 80% of THP-1 cells and 90% of U937 cells.

Conclusions: Our study suggests that co-targeting of Bcl-2 and NHE1 pathways not only sensitized the AML cells to venetoclax but also suggests that it could be one way to overcome venetoclax resistance in AML.

Disclosure: Nothing to declare.

Hannover Medical School, Hannover, Germany

Background: Outcome of allogeneic hematopoietic stem cell transplantation (alloHSCT) for acute leukemia (AL) is superior when performed in complete remission. Therefore, in refractory or relapsed patients not in remission after induction, consolidation or re-induction treatment, salvage strategies are being employed to reach at least marrow aplasia without residual blast morphology. Gemtuzumab-ozogamicin (GO), a humanized anti CD33 monoclonal antibody linked to calicheamicin, with a twisted drug history of early approval, withdrawal from the market, and renewed licensing for AML induction, has been an interesting candidate for such a strategy of “bridging to transplant” in CD33 positive AL patients.

Methods: We retrospectively evaluated overall (OS) and disease-free survival (DFS) of all adult refractory/relapsed AL patients having received GO for bridging to transplant at Hannover Medical School between 10/2004 and 12/2018. They were compared to a matched cohort of AL patients not reaching complete remission, but transplanted without bridging, since off-label GO could not be obtained for all refractory/relapsed patients.

Results: 232 refractory/relapsed AL patients underwent alloHSCT between 10/2004 and 12/2018 at our institution. 133 patients among them were CD33 positive. GO could be obtained for bridging to transplant in 32 patients, whereas 101 patients had to be transplanted without bridging. Both cohorts of CD33 positive patients were comparable for age, gender, disease subgroups, donor source, HLA matching, and conditioning intensity. GO salvage successfully induced marrow aplasia without residual blasts in 63% of evaluable patients. However, survival of CD33 positive AL patients after GO bridging (OS 29% at 5 and 10 years; DFS 27% at 5 years, 21% at 10 years) was not different from CD33 positive AL patients without GO bridging (OS 38% at 5 years, 28% at 10 years; DFS 32% at 5 years, 24% at 10 years). Of the total cohort of 232 refractory AL patients, 39% survived for 5 years and 32% for 10 years.

Conclusions: In our single center retrospective analysis of CD33 positive AL patients, bridging to transplant with GO seemed to have limited impact on long-term OS and DFS. However, even in refractory/relapsed AL, alloHSCT was able to rescue about one third of patients.

Disclosure: No conflicts of interest.

IRCCS San Raffaele Scientific Institute, Milan, Italy

Background: azacytidine (AZA) alone or with donor lymphocytes infusions (DLI) is an option for the treatment of acute myeloid leukemia (AML) relapsing after allogeneic stem cell transplantation (HSCT).

Methods: according to institutional policy, from 2012 to 2019 we treated 40 patients with AML relapsed after HSCT with AZA +/- DLI. Indications were either minimal residual disease positivity (MRD+) (evaluated by qPCR, flow cytometry or cytogenetical analysis) or morphological relapse not eligible for intensive chemotherapy. AZA dosage ranged from 32 mg/mq G1-5 to 75 mg/mq G1-7 q28 days. DLI was given every 2 cycles of AZA at escalating dose as per institutional guidelines. Indication to DLI relied upon clinical-biological features of patient, disease and HSCT (active GvHD and HLA loss were contraindications).

Results: clinical-biological features at baseline and at relapse are reported in Figure 1. Median time from HSCT to relapse was 10 months (range 1-55). Fourteen patients had MRD+ (group 1) and 26 patients had morphological relapse (group 2). Nine patients (23%) received AZA 32 mg/mq while 31 patients (77%) received AZA 75 mg/mq. Median number of AZA cycles was 4 (range 1-28). Sixteen patients (40%) received AZA+DLI, median number of DLI was 2 (range 1-4), median amount of CD3+ cells/Kg per patient was 3,8 x10^6 (range 0,1-76).

Overall response rate was 55% (22 pts): 57% (8 pts) in group 1 vs 54% (14 pts) in group 2 (p=0.87). Complete response rate was 33% (13 pts): 43% (6 pts) in group 1 and 27% (7 pts) in group 2 (p=0.43).

Progression free survival (PFS) at 1-year was 32%: 57% in group 1 vs 19% in group 2. At 2-years PFS was 23%: 57% in group 1 vs 7% in group 2 (p=0.01). In group 1, 7 patients maintained CR (4/7 received DLI) after a median follow up of 22 months (range 11-64). In group 2, 1-year PFS in patients with < 20% blast at relapse was 22% vs 12% in patients with ≥20% (p=0.24).

Overall survival (OS) at 1 year was 60%, respectively 85% in group 1 vs 46% in group 2. At 2-years OS was 41%: 77% in group 1 vs 22% in group 2 (p=0.01).

Most common grade 3-4 adverse events were neutropenia (80%), thrombocytopenia (55%), anemia (45%) and febrile neutropenia (35%). Acute GvHD developed in 3 patients (no one had previous GvHD, 1 received DLI) while 5 patients had chronic GvHD (2 had previous acute GvHD, 2 had previous chronic GvHD, 1 received DLI). No patient died because of treatment.

Conclusions: AZA +/- DLI is a feasible salvage therapy in relapsed AML after HSCT. AZA +/- DLI was rarely curative in morphological relapse - independently by blast counts - while long-term remissions were achieved in patients treated for MRD+ after transplant.

Disclosure: Nothing to declare.

Institute of Hematology and Blood Transfusion, Praha, Czech Republic

Background: Although allogeneic transplantation brings a substantial survival benefit in AML, post-transplant relapse remains one of the major events leading to treatment failure. Together with non-existing definite approach guidelines it causes difficulties in further treatment decision.

Methods: A retrospective survival evaluation of relapsed AML (n=148) patients after allogeneic transplantation between the years 1990 and 2019 was done. The decision of relapse treatment was performed individually with the respect to biological parameters of the disease, patient´s physical status and will. For the evaluation purpose the whole cohort was divided to 3 groups -1) no chemotherapy treatment except of immunosuppression tapering and DLI administration (n=44), 2) “low intensity “ treatment including low dose ARA-C, 5-azacytidine with immunosuppression modification and with or without DLI administration (n=36) and 3) “high intensity” treatment including intensive regimens with high dose ARA-C and anthracyclines preferentially with DLI or second transplant (n=68).

Results: The overall survival in 1, 2 and 5 years was 32%, 20% and 16%. There was an expected significant difference between not treated group (2%, 1%, and 1%) and treated group with no significant further difference between low intensity and high intensity groups (48%, 29% and 16% in high intensity group and 31%, 21% and 16% in low intensity group). Patients who relapsed earlier from transplant did worse in the first two years, but the difference disappeared in surviving patients after 24 months of relapse treatment. Not surprisingly patients who had achieved complete remission had significant OS advantage (71% vs 6% in 1 year and 52% vs 1% in 2 years). There was no survival advantage in treated patients without remission achievement to untreated patients at all, though among untreated patients there was one (1/36) fully responding to immunosuppression tapering. 34% of patients with remission achievement relapsed again. Treatment toxicity related death was in 21%. Another major contributor to death was GVHD.

Conclusions: The outcome of AML patients relapsing after allogeneic transplantation is very poor despite various treatment approaches. The survival benefit was seen in patients who achieved further remission, though the subsequent relapses were frequent. Treatment toxicity was rather high in this group of patients. The emphasis on prophylactic and preemptive treatment together with tight minimal residual disease monitoring should be carried out, and the introduction novel drugs (e.g. venetoclax, gilteritinib etc.) should be evaluated.

Disclosure: Nothing to declare.

CHU de Grenoble, La Tronche, France

Background: Approximately 60-70% of adult patients with newly diagnosed acute myeloid leukemia (AML) will achieve a complete remission after induction regimen. However resistant disease or relapse (R/R) remain a significant cause of treatment failure and a major unfavorable prognostic factor. Role and timing of allogeneic hematopoietic stem cell transplantation (HSCT) remains a matter of debate for these patients with R/R AML, as well as their transplant outcome. For these reasons, we have retrospectively analyzed the outcome of adult patients who underwent HSCT for R/R AML in our center at Grenoble University Hospital from 2007 to 2017.

Methods: Adults who had received HSCT in our center between 01/01/2007 and 12/31/2017 for R/R AML, at time of transplantation, were included. Progression-free survival (PFS) was the primary end point, while secondary endpoints assessed overall survival (OS), graft-versus-host disease (GVHD) relapse-free survival (GRFS), and cumulative incidences of GVHD, relapse and non-relapse mortality (NRM).

Results: This retrospective study reports data from 56 patients receiving HSCT for de novo or secondary R/R AML. The median age at transplantation was 56 years (range, 20-69 years). Median of marrow blasts was 13% (range, 5,5-78%). Half of the cohort underwent a myeloablative conditioning regimen, while 29% of the patients received a sequential regimen approach. Median follow-up was 52 months for surviving patients (range, 24-132 months), and the PFS at 1 year was 21,4% (95% Confidence Interval [CI], 11,9-32,9%), with a median of 98 days (95% CI, 64-149 days). Overall survival was 25% (95% CI, 14,6-36,8%) at 1 year, GRFS was 10,7% at 1 year (95% CI, 4,4-20,4%). Cumulative incidence of acute GVHD II-IV reached 47,8% including 13,6% of grade III-IV at 1 year, while 28,6% of patients were reported for chronic GVHD. Twenty four per cent of patients had a refractory disease at first assessment after HSCT. Relapse incidence was 62,7% (95% CI, 49,1-76,3%) at 1 year and progression of the disease was responsible for 53% of the whole cohort mortality. 88,5% of relapses occurred within the 6 first months following HSCT, and none appeared after the 8th month. NRM at 1 year was 32% (95% CI, 9,9-51,5%).

Conclusions: This study confirms the role of HSCT in R/R AML patients as the best curative approach available today, with similar outcome rates than previously published. No specific subgroup of patients was identified in terms of better outcome. However, the high incidence of early post-transplantation relapse reveals the persistent need to improve the procedure. The key points reported in larger trials are early donor identification, easier with the availability of haplo-donors, use of sequential conditioning regimen, early tapering of immunosuppression and post-transplantation maintenance, such as targeted therapies, hypomethylating agents, donor lymphocytes infusions or other forms of immunotherapies.

In conclusion allogeneic HSCT remains feasible in this poor prognosis subgroup of AML and a multicentric program is underway in Auvergne-Rhone-Alpes region, France, based on the harmonization of HSCT practices in this very high-risk AML patients.

Disclosure: No disclosure to declare.

First Pavlov State Medical University of St. Petersburg

Background: AML is the most common indication for alloHSCT. The EBMT manuscripts estimate the intermediate-risk ELN2017 patients as candidates for alloHSCT in CR1 from MSD. AlloHSCT from MUD is still a clinical option for this prognostic group. However, the outcome of relapsed AML remains poor, both due to low incidence of achieving a CR2 and higher NRM.

Methods: The study included 298pts for the period 2005-18, median(m) age was 36(18-70)years. The m follow-up was 24(13-168)months. Disease status: CR1 - 234(78%)pts, CR2 - 64(22%)pts. The favorable risk group(fav) included 50(17%)pts, the intermediate(int) - 200(67%)pts, and the unfavorable(unfav) - 48(16%)pts. AlloHSCT underwent 242pts, 178(74%)pts in CR1, according to ELN2017 fav - 21(12%)pts, int - 121(68%)pts and unfav - 36(20%)pts; in CR2 - 64(26%)pts, which were fav - 16(25%)pts, int - 36(56%)pts and unfav - 12(19%)pts. In int group alloHSCT was performed from MSD in 36pts and from MUD - 85pts. Chemotherapy (CT) received 56pts in the CR1 - 13(23%)pts in fav and 43(77%)pts in int ELN2017. Since 2013 PTCy has been used for the prevention of GVHD in alloHSCT and, since 2016 MAC consisted of fludarabine and busulfan14mg/kg.

Results: OS and RFS in fav were: after CT - 78%(95%CI57-99) and 72%(95%CI53-99), after allotHSCT in CR1 - 76%(95%CI59-95) and 71%(95%CI51-91), in CR2 - 86%(95%CI73-99) and 71%(95%CI48-94), p=.7 and p=.9. Relapse rate(RR) and NRM were 28%(95%CI6-56) and 10%(95%CI1-39), 24%(95%CI8-44) and 5%(95%CI1-20), 22%(95%CI5-48) and 13%(95%CI2-35), p =.6.

In int OS and RFS were: after CT - 42%(95%CI17-67) and 34%(95%CI15-53), after alloHSCT in CR1 - 77%(95%CI70-84) and 72%(95%CI65-79), in CR2 - 46%(95%CI27-65) and 45%(95%CI31-59), p=.02 and p=.03. RR and NRM - 60%(95%CI38-77) and 6%(95%CI6-19), 16%(95%CI10-25) and 12%(95%CI7-18), 26%(95%CI11-43) and 29%(95%CI15-45), p=.09 and p=.06.

After alloHSCT in unfav OS and RFS in CR1 were 43%(95%CI26-60) and 34%(95%CI17-51), in CR2 - 31%(95%CI4-58) and 30%(95%CI3-57), p=.4. RR and NRM were 60%(95%CI40-75) and 6%(95%CI1-17), 52%(95%CI18-77) and 18%(95%CI2-47), p=.8 and p=.2.

In int the year of alloHSCT was evaluated 2005-12 vs 2013-18. In CR1 the OS, RFS, RR and NRM were 64%(95%CI51-77) vs 85%(95%CI78-92), p=.01, 62%(95%CI48-76) vs 76%(95%CI64-88), p=.05, 20%(95%CI10-33) vs 16%(95%CI7-29) and 18%(95%CI8-30) vs 8%(95%CI3-16). In CR2 OS, RFS, RR and NRM were 30%(95%CI8-52) vs 65%(95%CI44-86), p=.3, 29%(95%CI7-51) vs 64%(95%CI42-86), p=.2, 34%(95%CI13-57) vs 12%(95%CI2-32) and 33%(95%CI13-55) vs 23%(95%CI7-45). In case of MSD 2005-12 vs 2013-18 in CR1 OS, RFS, RR and NRM were 58%(95%CI32-83) vs 78%(95%CI60-96), p=.2, 54%(95%CI29-79) vs 59%(95%CI34-84), p=.5, 32%(95%CI11-55) vs 36%(95%CI12-61) and 14% (95%CI2-36) vs 5% (95%CI1-21). After MUD alloHSCT 2005-12 vs 2013-18 in CR1 OS, RFS, RR and NRM were 67%(95%CI51-83) vs 87%(95%CI79-95), p=.07, 67%(95%CI50-84) vs 81%(95%CI67-95), p=.07, 13%(95%CI4-28) vs 10%(95%CI2-26) and 20%(95%CI8-36) vs 9%(95%CI3-18).

Conclusions: AlloHSCT should be delayed to CR2 for patients in the favorable risk group. In the unfavorable group, alloHSCT is indicated in CR1. Given the improvement of transplantation methods for patients of the intermediate group, alloHSCT is recommended in CR1. The outcome of alloHSCT from matched unrelated donor comparable with matched sibling donor. Patients with intermediate ELN risk AML should perform alloHSCT in CR1 despite of donor type (MSD or MUD).

Disclosure: Nothing to declare.

Jaslok Hospital and Research Center, Mumbai, India

Background: Post remission therapy in patients with acute myeloid leukemia (AML) consist of giving maintenance chemotherapy or allogeneic hematopoietic stem cell transplantation (AlloHSCT) in high risk patients as a curative therapeutic option. Conflicting results have been reported on the impact of ABO mismatch on various transplant outcomes such as neutrophil and platelet engraftment, acute and chronic graft versus host disease (GvHD), non-relapse mortality and overall survival.

Methods: We analyzed data of 58 AML (Acute Myeloid Leukemia) patients who had undergone Allo HSCT, between 2005 to 2019, at our Centre. In this study, we evaluated the demographic and clinical characteristics of patients, the effect of ABO mismatch and graft source on HSCT outcomes, such as engraftment and graft versus host disease (GvHD)

Results: Out of 58 patients, 30 (51%) were males, 28 patients were female. The median age was 31 years (range 3- 60) years. PBSC was the major source of graft, and matched sibling were the predominant donor type (97.1%). There were 26 patients with gender mismatch (44.8%). Among the recipients, ABO group mismatch was seen in 15 patients (25.8%), of which 12 cases were major blood group mismatch. Majority of patients received Bu-Cy as conditioning regimen (65.5%). The mean time to neutrophil engraftment was 14.6 days (SD 3.08) and platelet engraftment was 15.8 days (SD 4.69), which were similar in all patients irrespective of ABO match/mismatch status. (p=0.04 and p=0.05 respectively). 75.5% patients developed febrile neutropenia, of which 15% had documented infection with an identifiable microorganism. 13 cases (22.4%) developed acute GvHD, while 4 cases had VOD. 3 patients had transplant related mortality. Patients with fully matched sibling donor had statistical significant association with improved survival outcome (p 0.017). Both major and minor blood group mismatch were associated with increased mortality (p=0.05). On comparing different variables in terms of standard deviation using unpaired t test, age at transplant was the only variable with significant association with survival outcome (p.0.003).

Conclusions: Our experience with ABO mismatch is encouraging with good tolerability and disease control even in the advanced stage heavily pre-treated patients. More aggressive strategies including second transplants and novel agents are needed in these patients on relapse.

[overall survival]

Disclosure: No conflict of interest. This study was not funded

Royal Marsden Hospital, London, United Kingdom

Background: Outcomes in elderly AML remain poor due to high risk of relapse, higher incidence of adverse cytogenetics and of chemotherapy resistance. The advent of reduced intensity conditioning (RIC) regimens has led to increasing use of allogeneic transplant in patients over the age of 60. This can lead to durable disease free survival in this age group and improved outcomes compared to that achieved with chemotherapy alone

Methods: This retrospective study analysed outcomes of 100 consecutive patients over the age of 60 years old undergoing RIC SCT for AML between June 2006 and June 2018. Patients were conditioned with Fludarabine/Melphalan/Alemtuzumab (n=94) or Fludarabine/Cyclophosphamide/2GyTBI (n=6). Data was collected from Electronic patient records. Probability of Overall Survival (OS), Progression Free Survival (PFS) were calculated by Kaplan Meier method and log rank test performed. Cumulative Incidence (CI) of relapse risk (RR), non-relapse mortality (NRM) and GVHD was calculated using competing risk analysis

Results: 100 patients were included in the study with a median age of 65 years (range 60-1 - 71.8). 77% had De Novo AML, 13% had a preceding diagnosis of MDS or MPD, 10% had therapy related AML. 79% of the patients were transplanted in CR1 and 21% were transplanted in CR2. 34 patients relapsed at a median of 0.96 years post transplant (range 0.11-5.37). 53% of patients had a matched Unrelated Donor (MUD) SCT, 23% sibling donor, 18% Mismatched unrelated donor (MMUD) and 6% umbilical cord blood (UCB) donor. 39% of patients had adverse prognostic markers at diagnosis as per ELN 2017 guidelines.

2 year OS was 41% and 2 year PFS was 36%. RR at 2 years was 25% and 2 year NRM was 38%. CI of Grade 2-4 acute GVHD at Day 100 was 15% (9-23) and 2 year CI of chronic GVHD was 30%. 2 year OS for patients with sibling, MUD, MMUD and cord donors was 61%, 40%, 67% and 22% respectively and 2 year PFS for patients with sibling, MUD, MMUD and cord donors was 56%, 35%, 67% and 17% respectively. OS was significantly reduced in those with MMUD donors compared to sibling (p=0.009%) and MUD donors (p=0.04%) due to higher NRM. Age at transplant (< 65 years versus >/=65 years), transplant in CR1 versus CR2 and adverse versus non adverse risk group had no significant impact on OS or PFS.

Conclusions: T cell depleted RIC allogeneic HSCT can lead to durable disease free remissions in older patients with AML including patients with adverse risk disease or therapy related or secondary AML. Patients with MMUD had inferior OS and PFS compared to those with a sibling or MUD donor in this age group and the decision to perform a mismatched unrelated donor transplant in this age group should be carefully assessed. Whilst numbers of UCB were small, the of use of alternative donors rather than MMUD in this age group should be considered and warrants further evaluation in randomised setting

Disclosure: Nothing to declare.

¹Universitätsklinikum Jena, Jena, Germany, ²Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany

Background: Myeloid sarcoma (MS) as a solid extra-medullary manifestation of acute myeloid leukemia (AML) is a rare presentation of relapse after allogeneic hematopoietic stem cell transplantation (HSCT). It may occur as an isolated extra-medullary relapse, multilocular or in association with a medullary relapse.

Methods: All patients aged 18 years or older who have received HSCT for AML at our center since 2002 (n = 327) were screened for onset of MS after HSCT. Of those, 12 patients (3.7%) suffered from MS as extra-medullary relapse after HSCT and were included in this study.

Results: We identified 12 patients (median age 53 years) with MS. They all received reduced intensity conditioning (RIC). 58.3% (7/12) received HSCT from a matched-unrelated, 33.3% (4/12) from a matched-related and 8.3% (1/12) from a mismatched-related donor. The median onset of MS was 490.5 days after HSCT (range: 134 and 1276 days). The regions and organs affected varied from very typical tissues such as skin, bone or lymph node up to extremely rare presentations of MS affecting the pituitary gland, breast tissue, the thoracic wall or the paranasal sinuses. Eight (66.7%) patients developed MS despite a history of graft-versus host-disease (GvHD).

Concerning the treatment, various therapy options were considered. The most frequently applied treatment options were intrathecal triple therapy, cytarabine and azacytidine. None of the patients received another HSCT. Irradiation was implemented where possible. Although MS is associated with a poor prognosis, three patients (3/12) survived more than two years and one more than 11 years after diagnosis of MS. The median overall survival since diagnosis of MS was 255.5 days (Kaplan-Meier).

Conclusions: These observations demonstrate the limitations of graft-versus-tumor effects after HSCT, since extra-medullary relapse did occur in the presence of GvHD. The results may also indicate that reduced intensity conditioning protocols are associated with a higher rate of extra-medullary relapse.

Single isolated manifestations are more frequently treated successfully compared to multilocular manifestations of MS. This is in part due to fewer issues regarding accessibility by local therapies such as irradiation or intrathecal therapy (in cases of involvement of the central nervous system). Altogether occurrence of MS after HSCT is associated with a poor prognosis as curative concepts including intensive chemotherapy and another HSCT are often not viable.

Disclosure: The authors do not declare. any conflicts of interest.

¹Charles University Prague, Hradec Kralove, Czech Republic, ²University of Defence, Hradec Kralove, Czech Republic

Background: Allogeneic stem cell transplant remains the best consolidation therapy in intermediate and high-risk AML patients with a suitable donor. We conducted a retrospective analysis to identify those who may benefit from further intensification of therapy.

Methods: Eighty patients, aged 53.5 ± 12.6 years, diagnosed in period 2010-2016 were studied. All were treated with a curative approach with “3+7” induction therapy, followed by consolidation only of allogeneic stem cell transplantation. All living patients have been observed for at least two years. The FLT3 inhibitors were not used in this cohort.

Results: 55 patients (69%) achieved complete remission (CR) by induction therapy. 57 patients (71%) were allografted. Hematologic relapse (P < 0.001), high-risk cytogenetics (P = 0.001) and age (P = 0.033) influenced overall survival (OS). Patients relapse-free for at least two years (irrespective of consolidation by chemotherapy only or allografted) had low risk of relapse and longer OS (P < 0.001). Allografted patients were younger (P = 0.009) and had improved OS (P = 0.010). Patients aged ≥ 65 years had lower probability of prolonged remission and inferior outcome. Primary induction failure (PIF) in low- and intermediate risk AML (n = 8/47, 17%) was not associated with inferior OS. In high-risk AML and PIF (n = 14/33, 42%) the median OS was 6.7 months in the whole cohort, respectively 12 months in 8 allografted individuals.

Conclusions: In patients with low- and intermediate risk AML and PIF the allogeneic stem cell transplant may overcome the resistance to induction therapy. A substantial proportion of PIF patients have high-risk AML. The efficacy of allogeneic stem cell transplant is limited in this cohort and the overall survival is poor. These patients may most benefit from innovative treatment approaches.

The work was supported by program PROGRES Q40/08, and by DZRO 1011 (FMHS).

[PIF in high-risk AML]

Clinical Trial Registry: Not applicable.

Disclosure: Nothing to declare.

¹Unità di Terapia Intensiva Ematologica per il Trapianto Emopoietico, Ospedale Civile, Pescara, Italy, ²Laboratorio Genetica Molecolare Onco-Ematologica, Ospedale Civile, Pescara, Italy

Background: Patients with acute myeloid leukemia (AML) who did not achieve remission after first induction chemotherapy have a dismal prognosis. Prior reports have shown that these patients could be rescued with allogeneic hematopoietic cell transplantation (HCT). The aim of this retrospective study was to determine the clinical outcome of 34 AML patients who failed first induction chemotherapy and were treated with HCT (n=40) in our center between June 1995 and April 2019.

Methods: 34 patients with AML who did not achieve complete remission (CR) after first induction chemotherapy with “7+3” regimen (cytarabine associated to either daunorubicin or idarubicin) were enrolled in this study. As second induction chemotherapy, most patients received high dose cytarabine-based regimen. The median number of chemotherapy lines before transplantation was 2 (range, 2-3). The median time from diagnosis to first CR was 106 days (range, 63-225). At time of HCT, 30 patients were in CR1, 2 in CR2 and 2 in partial remission (marrow blasts 6-10%). Table 1 shows some characteristics of patient population at time of first transplant.

Results: Full engraftment of donor cells was evident in 31 evaluable patients (91%). 2 patients died before engraftment and 1 patient showed primary graft failure. The median time to reach >0.5 x10⁹/L neutrophils was 23 days (range, 13-35). The CI of either acute (grade II-IV) or chronic (limited + extensive) GvHD was 32% and 21% respectively. Leukemia relapse occurred in 13 patients at a median of 411 days (range, 67-1824) after transplant for a CI of 42%. Of them, 5 died for leukemia, 6 underwent a second transplant after achieving second CR, 1 is waiting for second HCT and 1 is leukemia-free after sorafenib therapy. Among 6 patients who received a second transplant, 2 are living and cured, 2 died for infections, 1 died for VOD and 1 died for leukemia relapse. Nine patients died for transplant-related causes at a median of 53 days (range, 8-740) after transplant. Causes of death were infection in 5, acute GvHD in 2, and heart failure in 2. The 3-year-CI of transplant-related mortality was 27%. As of November 2019, 16 patients are living and doing well after a median follow-up of 116 months (range, 7-264). Of them, 15 (44%) are cured and 1 is waiting for second transplant. The 5-yr Kaplan-Meyer overall survival and disease-free survival were 47% and 29% respectively.

Conclusions: This study demonstrates that allogeneic HCT may produce durable remission and cure in patients with AML who failed first induction chemotherapy.

[Table 1]

Disclosure: Nothing to declare.

Aplastic anaemia

¹Shanghai Children’s Medical Center, National Children’s Medical Center, Shanghai, China, ²The Sixth Medical Center of PLA General Hospital, Beijing, China, ³West China Second University Hospital/West China Women and Children’s Hospital, Chengdu, China, ⁴BaYi Children’s Hospital, The Seventh Medical Center of PLA General Hospital, Beijing, China, ⁵Fujian Medical University Union Hospital, Fuzhou, China, ⁶Anhui Provincial Hospital, University of Science and Technology of China, Hefei, China, ⁷Children’s Hospital of Soochow University, Soochow, China, ⁸BeiJing JingDu Children’s Hospital, Beijing, China, ⁹Guangzhou First People’s Hospital, Guangzhou, China, ¹⁰Changhai Hospital, Naval Medical University, Shanghai, China, ¹¹Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ¹²Ruijin Hospital, Shanghai Jiao Tong University, Shanghai, China, ¹³Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China

Background: It is generally recognized that allogeneic hematopoietic stem cell transplantation (allo-HSCT) should not be managed to patients with active infection. However, in patients with severe aplastic anemia (SAA) especially very severe aplastic anemia (VSAA), it is usually difficult to control the infection without neutrophil. Rapid recovery of neutrophil by allo-HSCT might be a salvage treatment to control infection and rescue the patients. To evaluate the efficacy of allo-HSCT for SAA patients with refractory active infection, we designed this multicenter prospective clinical study in China.

Methods: Refractory active infection was defined as persistent fever without response to broad-spectrum antibacterial and antifungal treatment for more than three weeks with or without a definite infected site, or there was a definite infected site with fever less than 3 weeks. The probabilities of overall survival (OS) were calculated using the Kaplan-Meier estimator and compared between two groups using the log-rank test. The cumulative incidences were calculated using competing-risk models and analyzed by the Grey test between groups.

Results: Totally 75 patients were enrolled in this study from April 2014 to July 2018. All patients had persistent fever, including 52 (69.3%) with pneumonia (13 also accompanied with other site infection), 16 (21.3%) with other site infection and another 7 (9.3%) without a definite infected site. 51 (68.0%) patients received HSCT from a haploidentical family donor, 15 (20.0%) from an unrelated donor and only 9 (12.0%) from a sibling donor. For the prompt engraftment, peripheral blood stem cells (PBSCs) were given to all of our patients. Meanwhile, bone marrow was co-transplanted with PBSCs in 40 (53.3%) patients. The median age was 6.3 years (range, 1.0-38 years). Seven (9.3%) patients died of infection before engraftment. Two (2.7%) patients got primary mixed chimerism at day 28, and one developed secondary graft failure. The other patients sustained complete donor chimerism after HSCT. The median time for myeloid engraftment was 13 days (range, 9 to 32). The cumulative incidences (CI) of II-IV acute GVHD and chronic GVHD were 18.7±4.5% and 24.0±5.0% respectively. With a median follow-up of 730 days (range, 2 to 1568), the probability of OS was 77.2±4.9%. Because 68% of patients underwent haploindetical transplant, we compare the outcomes of patients receiving haploindetical transplant with active infection (n=51) to that of patients receiving haploindetical transplant without active infection (n=73) during the same period. There were no statistic differences in the CI of II-IV acute GVHD (17.6±5.4% vs 19.2±4.6%, p=0.771), CI of chronic GVHD (25.5±6.2% vs 20.5±4.8%, p=0.371), and the probability of OS (78.3±5.8% vs 89.0 ±3.7%, P=0.096) between the two groups. Compare to the other donor, the FFS II-IV, aGVHD and chronic GVHD with haploidental donor HSCT is simila to other donors.

Conclusions: Allo-HSCT is a feasible therapeutic option for SAA patients with refractory active infection. Haploidentical family donor is a good donor if without matched sibling donor. Peripheral blood stem cell may be the better graft source for this salvage HSCT owing to the rapidly engraftment.

Clinical Trial Registry: Clinical Trail registry number: ChiCTR-OCH-14005190

http://www.chictr.org.cn

Disclosure: Nothing to declare.

¹University Hospital Donostia, Donostia, Spain, ²Hospital Virgen de la Victoria, Málaga, Spain, ³ICO-Hospital Germans Trias i Pujol, Badalona, Spain, ⁴Hospital General de Alicante, Alicante, Spain, ⁵Hospital Álvaro Cunqueiro, Vigo, Spain, ⁶Hospital Clínico San Carlos, Madrid, Spain, ⁷Hospital La Fe, Valencia, Spain

Background: Aplastic anemia (AA) is a rare, and life-threatening hematological disease. It is known that its incidence and prevalence might vary substantially among different geographic regions, and its presentation has been sometimes linked to environmental exposures. Montané et al reported an incidence of 2.34 per million inhabitants per year in the metropolitan area of Barcelona (Haematologica 2008). In the north of Spain, our group found 2.49 new cases/year (EBMT 2016). In Sweden, an incidence of 2.35 new cases/year has been recently reported (Vaht, Haematologica 2017). Our aim was to know the incidence and epidemiology of AA in a well-defined population.

Methods: In an ambispective study (IMAS), 7 general hospitals from 7 provinces situated in different geographical regions, that take care of a population of around 3.91 million inhabitants, participated in this study. All the patients diagnosed with AA were included. Data bases of the Hematology, Pathology, and Pharmacy Departments were used as a source of information.

Results: During the period 01/01/201031/07/2019, 103 new cases were identified (3-14 cases/year). The incidence of AA was 2.75 per million inhabitants per year. The median age at diagnosis was 56 years old (11-85), and gender was distributed almost equally between females and males. More than half of the cases were severe or very severe, and 9 out of 10 of the patients had transfusion needs. The most frequently employed approach at first line was immunosuppressive therapy with ATG/cyclosporine A (CsA). HSCT was a very infrequent 1st line therapy. At 1 year, two-thirds of the patients were in response (partial or complete). With a median follow-up of 6 years, threequarters of the patients were alive. See table.

[Table. Description of the series]

Conclusions: 1) Worldwide, there are few studies focus on the epidemiology and management of AA patients. Particularly, this is the first national study of these characteristics ever performed in Spain; 2) We found an incidence of AA of 2.75 new cases/year; 3) No differences in gender were found; 4) ATG/CsA was the most frequently employed first-line therapy; 5) Long term response rate we found are similar to those shown in previous international reports of AA patients, and clearly show that there is an important room for improvement with new therapeutic approaches.

Disclosure: Nothing to declare.

Nagoya University, Nagoya, Japan

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for children with severe aplastic anemia (AA). With the improvement in HLA typing resolution and advancement of supportive care for graft-versus-host disease (GVHD), various donor options are available for patients without HLA-matched sibling donors, such as unrelated donors, HLA-mismatched family (haploidentical) donors, and cord blood (CB). This retrospective study aimed to evaluate the HSCT outcomes from these donors.

Methods: Treatment outcomes of 65 children with AA (aged < 20 years) who underwent HSCT between 1991 and 2018 in our institute were analyzed. Unrelated donors were matched to patients at the allele level of HLA-A, HLA-B, HLA-C, and DRB1. Patients were divided into three groups: serologically matched or one-locus mismatched related donors (MRD/1MMRD, n = 37), 8/8-matched unrelated donors (MUD, n = 9), and alternative donors (AD, n = 19). AD was further divided into 7/8-matched unrelated donors (7/8MMUD, n = 9), serologically 2-3 mismatched related donors (Haplo, n = 6), and CB (n = 4). Treatment failure was defined as death from all causes, graft failure, and second malignancy.

Results: The median age at HSCT was 11.2 (range, 1.3-18.8) years. The median follow-up period was 69 (range, 1-196) months. Differences were found in the median follow-up according to the donor source, which was longer in MRD/1MMRD and AD, 93 and 45 months, respectively, and shorter in MUD, 18 months (P < 0.001). The median time from diagnosis to HSCT was 9 (range, 0-135), 11 (2-78), and 11 (0-69) months for MRD/1MMRD, MUD, and AD groups, respectively (P = 0.627). Neutrophil engraftment was achieved after HSCT in all patients. The median day of neutrophil recovery was day+18 (range, +11 to +36). Two patients experienced second graft failure, and all of them were in the AD group (Haplo, n = 1; 7/8MMUD, n = 1). Cumulative incidences of grade II-IV acute GVHD were 5% (95% confidence interval [CI], 0%-12%), 0%, and 21% (95% CI, 0%-37%) for MRD/1MMRD, MUD, and AD, respectively (P = 0.092). The 3-year cumulative incidences of chronic GVHD were 8% (95% CI, 0%-17%), 30% (95% CI, 0%-58%), and 16% (95% CI, 0%-32%) for MRD/1MMRD, MUD, and AD, respectively (P = 0.241). The 5-year overall survival was not significantly different among the three groups (MRD/1MMRD, 97% [95% CI, 82%-100%]; MUD, 88% [95% CI, 39%-98%]; AD, 100%; P = 0.266). The cause of death was infections without graft failure in two patients (MRD/1MMRD, n = 1; MUD, n = 1). Failure-free survival (FFS) was tended to be lower in the AD group (MRD/1MMRD, 97% [95% CI, 82%-100%]; MUD, 88% [95% CI, 39%-98%]; AD, 79% [95% CI, 53%-92%]; P = 0.082).

Conclusions: The overall survival rate of HSCT from both MUD and AD in children with AA is comparable to those from MRD/1MMRD. However, the algorithm for donor selection should be considered according to FFS. Further study with a larger number of patients is needed to determine the preferable AD.

Disclosure: The authors declare. no conflict of interest.

King Faisal Specialist Hospital & Research Center, Jeddah, Saudi Arabia

Background: Severe Aplastic Anemia (SAA) is a rare hematological disease characterized by pancytopenia and a hypo cellular bone marrow in the absence of abnormal infiltrates. Allogeneic hematopoietic stem cell transplantation (HSCT) is the current available curative treatment, however for patients who lack matched sibling donor (MSDs), immunosuppressive therapy (IST) is widely accepted as an alternative first-line treatment. Outcome data of children with acquired aplastic anemia (AA) are lacking from our region.

Methods: Laboratory and clinical information of all children < 18 years of age with acquired SAA diagnosed between January 2005 and December 2015 at KFSH&RC were retrospectively collected. Relevant details about treatment given i.e. IST and HSCT, treatment outcome, overall survival (OS) and event free survival (EFS) were also recoded. An events were defined as death, treatment failure, or rejection.

Results: Thirty children were included in the study. Fifteen (50.0%) patients were female and 18 (60.0%) patients underwent matched family donor (MFD) HSCT while the remaining patients received upfront IST. Three-year OS and EFS for children undergoing upfront MFD HSCT was 100%. Out of twelve children treated with IST, three were evaluable for response. Two children died before receiving a rescue transplant. Seven of the patients failed upfront IST and received rescue transplants, of these two children died with infection and rejection. The OS of the patients who received rescue after failed IST was 70% and there EFS was 71%. The overall response to IST was seen in three out of twelve (25%) patients with two patients achieving complete response while one patient had a partial response. The 3-year estimated OS and EFS for children treated with IST was 66.6% and 15% respectively.

Conclusions: We observed an inferior outcome in patients who received immunotherapy in our study comparison to published international literature. This could be explained by higher prevalence of consanguineous marriages in the Saudi population and their genetic background. Alternative transplant modalities should be considered for those who lack matched family donor.

Disclosure: no conflict of interest

University Hospital Essen, Essen, Germany

Background: Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is still the standard treatment for acquired severe aplastic anemia (SAA) in patients younger than 40 years with sibling donors. Sufficient and durable reconstitution of haematopoietic donor stem cells is important for successful allo-HSCT. Poor graft function (PGF) after allo-HSCT is characterized by persistent pancytopenia, immunodeficiency and dependence on blood transfusions, despite of a complete donor chimerism. The probability of developing PGF seems to be increased in the absence of a regulatory bone marrow stromal microenvironment, even in cases where bone marrow is used as a source of stem cells.

Aim: To evaluate in a single-center retrospective analysis the long-term transplant outcome considering haematological recovery and overall survival (OS) in patients (pts) with SAA after allo-HSCT requiring CD34⁺-selected stem cell boosts.

Methods: The analysis comprises data of 35 pts with aplastic anemia after allo-HSCT from HLA-matched sibling (n=14) or unrelated (n= 21) donors, who underwent allo-HSCT between 2006 and 2018. The median age of the 26 male and 9 female pts was 28 years (range, 17 to 66). A myeloablative conditioning regimen was used in 6 pts, while 29 pts were treated with a reduced intensity immunosuppressive conditioning regimen. Bone marrow (n=20) or peripheral blood stem cells (n=15) with a median of 3.89 x 10⁶ CD34⁺ cells/kg bodyweight (BW) (range, 1.4 to 14.6) were transplanted. PGF was diagnosed in 16 pts with a median of 46 days (range, 40 to 106) after allo-HSCT by bone marrow biopsy. The stem cell boost was performed using immunomagnetically selected CD34⁺ stem cells from original donors. The boost stem cell dose was 6.1 x 10⁶ CD34⁺ cells/kg BW (range, 0.95 to 13.25). Statistical analysis was performed on with SAS 9.4 using the method of Fine and Gray for competing risk cumulative incidences and Kaplan Meier estimates for overall survival.

Results: The rate of complete hematological engraftment was 94% (33 of 35 pts), including 16 pts with CD34⁺-selected stem cell boosts infusion for poor graft function performed. The median time to recovery was 34 days (range, 16-100) for neutrophils and 62 days (range, 11-175) for platelets. The current 10-year survival rate is 80%. (without boost - 89.5%, with boost - 68,7%, p=0.03). No relapse of SAA developed. Seven (20%) pts died as a result of infectious complications (n=6), hemolytic uremic syndrome (n=1).

Hematological reconstitution in patients with or without CD34+ stem cell boosts - is presented in table 1.

Conclusions: The use of CD34+-selected peripheral blood stem cell boosts from the original donor allows a complete, albeit delayed regeneration of haematopoiesis in the majority of aplastic anemia patients with PGF after allo-HSCT. The leading causes of deaths were severe infectious complications due to prolonged cytopenia after allo-HSCT in this patient subset.

[Table 1. Hematological reconstitution after allo-HSCT in patients with SAA]

Disclosure: Bogdanov: Neovii Biotech, Jazz Pharmaceuticals, MSD.: Other: Travel subsidies. Beelen: Medac GmbH Wedel Germany: Consultancy, Honoraria. Turki: Jazz Pharmaceuticals, CSL Behring, MSD.: Consultancy; Neovii Biotech, all outside the submitted work: Other: Travel subsidies.

Ampang Hospital, Ampang, Malaysia

Background: Hematopoietic stem cell transplant (HSCT) provides curative therapy in almost 90% of patients with severe aplastic anemia (SAA). Older age, long duration of disease with consequent heavy exposures to transfusion and active infection at the time of HSCT have a negative influence on outcome, favouring graft failure (GF) and graft versus host disease (GVHD). This study aimed to evaluate outcome of all SAA patient who received hematopoietic stem cell transplantation at a tertiary centre in Malaysia.

Methods: Data was obtained from transplant database and patients’ medical record at Ampang Hospital, Malaysia. Patients with acquired SAA who underwent HSCT between January 1999 until November 2019 were included. Demographics, clinical characteristics and treatment outcomes were collected and analyzed using descriptive statistics.

Results: A total of 84 cases were identified for this study with mean age of 23.7 ± 10.0 years. Fifty-eight percent of the cases were male (n=49). Malay ethnicity were the highest (51.8%) followed by Chinese (24.1%) and Native Sabah (14.4%). Majority were transplanted within 6 months of diagnosis (n=58, 69%) and out of this number, 20% received transplantation within six weeks. Forty-five cases (53.6%) used peripheral blood as stem cell source, 36 cases (42.%) used bone marrow and three cases (3.5%) used both. Most of the patients (60.7%) received non-Fludarabine based, Cy (cyclophosphamide)-ATG (anti thymocyte globulin) as their conditioning regime. Mean engraftment for neutrophil was 14.9 (range 6 - 29) days and 15.1 (range 8 - 35) days for platelet. Patients who underwent peripheral blood stem cell transplant had significant early engraftment for neutrophil (p < 0.01) in comparison to bone marrow. However, this finding is not observed with platelet engraftment. Twenty-nine cases (34.5%) died within 100 days of transplant from treatment-related complications (n=23), disease progression (n=4) and others (n=2). Four of the transplanted patients required second allogeneic transplant due to secondary graft failure, however only one survived.

Conclusions: This study shows that only small percentage of cases were transplanted less than six weeks from diagnosis. Early transplant strategy is necessary to improve outcome among patients with SAA. Further study is required to look into the factors leading to delay in diagnosis and treatment among them.

Disclosure: Nothing to declare.

Mazumdar Shaw Medical Center, Narayana Health City, Bengaluru, India

Background: Hematopoetic stem cell transplant (HSCT) is the only curative option for progressive marrow failure in Fanconi Anemia (FA). There is paucity of data on HSCT for FA from India, especially using haploidentical donors. We report our experience of allogeneic transplants for FA.

Methods: We retrospectively analyzed the records of 13 children who underwent 15 HSCTs from 2014 to 2019.

Results: A total of 13 children underwent 15 HSCTs. The median age was 92 months (27-235). The donors were: Haploidentical donor (n=6), HLA matched siblings (n=5) and HLA matched related donor (n=2). Graft source: Bone Marrow (n=7); PBSC (Peripheral blood stem cells) (n=-8). Among haploidentical transplants, the graft source was T-cell depleted (TCD) PBSC in five and T-Cell replete (TCR) in one. The depletion method was TCR alpha/beta with CD19 + cell depletion using CliniMacs system. Conditioning regimen: Fludarabine/Cyclophosphamide (total dose of 40 mg/kg) and ATG in 14 (along with TBI in one), Treosulphan-Flu-Cy-ATG in one and Fludarabine-Busulfan-ATG in one. GvHD prophylaxis: Cyclosporine & Mycophenolate Mofetil in MSD/MRD HSCTs, Sirolimus in Haploidentical HSCTs with TCD grafts and Post-transplant cyclophosphamide (25mg per kg for 2 days), CSA and MMF in Haploidentical HSCT with TCR graft. The median infused CD34+ cell count was 7.8 × 10⁶/kg (range 3.42-21.5× 10⁶/kg). Of the 13 patients who underwent transplant, 10 engrafted with a median neutrophil and platelet engraftment at day 11 and 12 respectively. Three did not engraft (2-Haplo with TCD PBSC, 1-MRD with Marrow) -of which two engrafted after second transplant, one child had donor specific antibodies and expired secondary to infection. All the four who had acute GvHD received TCR stem cells (3-marrow, 1-TCR PBSC from haploidentical donor). Four patients had chronic GvHD (all were matched sibling/related, 3-Marrow, 1-PBSC) of whom one expired from severe bronchiolitis obliterans and the rest are alive with moderate skin GvHD. Interestingly, none of the patients who received TCD PBSC developed either acute/chronic GvHD. All alive patients developed full donor chimerism and are disease free. One achieved full donor chimerism after donor lymphocyte infusions for mixed chimerism. Day 100 survival rate was 76.9%. (10/13). OS: For entire cohort - 69.2 %, for haploidentical HSCT cohort -66.7% (4/6) at a median follow up of 211 days.

[Allogenic transplant outcomes in Fanconi Anemia (N=13, Number of transplants=15)]

Conclusions: HSCT for FA has good outcomes with reduced intensity conditioning regimens. Haploidentical donors are alternatives in the absence of matched donors with reasonably good outcomes and minimal GVHD rates using TCD stem cell source.

Disclosure: Nothing to declare.

Akdeniz University, Antalya, Turkey

Background: Aplastic anemia (AA) is a life-threatening form of bone marrow failure characterized by pancytopenia and hypo cellular marrow. The pathogenesis of the disease is thought to involve autoimmune process and it is associated with very high mortality if left untreated. Allogenic hematopoietic stem cell transplantation from a HLA-MRD is the preferred treatment in children and young adults. But when MRD is not available immunosuppressive therapy with CsA and ATGAM or transplantation from an alternative donor are the therapeutic options.

Methods: We retrospectively analyzed the data of AA patients who underwent HSCT at Pediatric Stem Cell Transplantation Unit of Akdeniz University Hospital from January 2000 to December 2017.

Results: A total of 31 HSCT was conducted over 28 patients during this period. There were 19 boys and 9 girls with a median age of 10 years (range: 3.4-19.8) at transplantation. Eighteen patients have previously received immunosuppressive agents but were unresponsive to the treatment. Ten patients were receiving regular blood products before transplantation. The source of HSCT was PBSC in 16 and BM in the rest 15 transplantations. Patients received HSCT as graft from a matched unrelated donor (n:15), from a matched sibling donor (n:10), from a matched family donor (n:5), and from a haploidentical donor (n:1). All patients received FLU or CY based reduced intensity conditioning regimens and GVHD prophylaxis comprised a calcineurin inhibitor plus methotraxate in 90% of patients. The median infused CD34+ cell dose was 4.9 ×10⁶/kg (range:1.2-18.2×10⁶/kg). Within a median follow up of 55 months (range: 2-206) after transplantation, 5-year overall survival was 78% in the total group and there was no statistical significant difference between the MRD and MUD groups (92% vs. 53% p=0.13). Grade III-IV aGVHD occurred after 3 of the transplantations (10%). Six patients died at a median of 9 months (range: 2-88) after transplantation.

Conclusions: Our results show that HSCT for AA patients has promising results and transplantation from unrelated donors are approaching those of MRD transplants. Application of immunosuppressive drugs, treatment rabbit ATG instead of ATGAM in previous years, and delay of transplantation waiting for appropriate donor might be the reasons for poor survival in MRD group.

Disclosure: Nothing to declare.

Ain Shams University, Cairo, Egypt

Background: Aplastic anemia (AA) is life threatening disorder in pediatric age group with increasing incidence nowadays, with hematopoietic stem cell transplant being the 1st line therapy; immunosuppressive therapy (IST) is the alternative therapy and is the most commonly used modality of treatment especially. in the developing countries

Methods: We aimed to assess the outcome of IST in children with AA. Data for 25 children treated with IST from January 2014 to January 2019 (5 years) were retrieved from clinic records. IST included rabbit anti thymocyte globulin (ATG) along with cyclosporine A and another group were treated by sand immune alone

Results: Patient characteristics include median age (9) with 73 %male and 26.1 %female. with median interval between diagnosis and start of IST(0.5 -1) and around 30.4 % with hepatitis A associated aplastic anemia. Complete response, partial response and nonresponse was seen in 4 (37.5) (0%) and 1(12.5%) patients, respectively in patients received ATG and sandimune. while in patients received sandimune alone complete response and no response was seen in 7(46.7Z%) and 8 (53.3%) respectively. The median time to best response in the whole cohort was 12 months. There was no difference in outcome related to severity of AA, or higher ALC. There was a significantly better rate of response (p value: .03) in both groups of patients with higher Hb level, HCT, and PLT level before start of IST. An overall response rate in both groups around of 39.5% reported a 5-year OS of 50% with 16% of patients with complete response with HAAA. A delayed time to complete response with prolonged requirement of cyclosporine therapy was detected

Conclusions: In a developing country setting, IST with ATG and cyclosporine seems to be an alternative treatment for aplastic anemia in children lacking MRD.

Clinical Trial Registry: not applicable

Disclosure: Nothing to declare.

HCG Manavata Hospital Nashik, Nashik, India

Background: Treatment of Aplastic anemia mainly consist of ATG+CSA or Hematopoietic stem cell transplantation. Due to financial constraints majority of patients cannot opt for these available treatment options. The patients who arrange the cost of HSCT, needs supportive care until the definitive treatment (transplant or ATG) is done. The cost of SDP and PCV and antibiotics for infection is a major hurdle to arrange the funds for BMT. To reduce that, we have used combination of CSA, Danazol and Romiplastim as a bridge to BMT in our five patients of Aplastic anemia.

Methods: A retrospective study in a cohort of patients with AA. The study was conducted from January 2018 to December 2019. Romiplostim (5ug/kg) SC once a week was used for 4-8 weeks. Cyclosporine 5mg/kg per day was used to keep level between 150-200. Danazol was used 100 mg TDS, dose was increased upto 600 mg/day after monitoring liver function test.

Results: Five patients with a mean age of 47 (18-83) years were included in the study. Four patients achieved some form of remission (partial/complete), one patient died, one patient is in complete remission, and one underwent HSCT successfully. Two patients are in partial remission waiting for the HSCT.

Conclusions: Improved response rates with triple therapy was observed in patients with severe AA. The triple therapy can be used as a bridge for definitive treatment in Aplastic Anemia.

Disclosure: None

Autoimmune diseases

¹University of Liverpool, Liverpool, United Kingdom, ²The Christie NHS Foundation Trust, Manchester, United Kingdom

Background: Multiple Sclerosis (MS) is a chronic, progressive, central neurological disease mediated by autoimmunity. Despite availability of anti-inflammatory drugs such as alemtuzumab, disease progression still occurs with minimal initial reversal of symptoms. Autologous haematopoietic stem cell transplantations (aHSCT) for treatment of MS has seen more dramatic reversal in symptoms but have not been previously directly compared to alemtuzumab.

Methods: Systemic review of cohort studies and randomised control trials (RCTs) of Relapsing Remitting MS (RRMS) patients treated with alemtuzumab or aHSCT.

Results: aHSCT.

A total of 144 studies met the search criteria. After application of eligibility criteria and removal of duplicate data, six studies including 277 patients with RRMS, who failed initial DMTs, were included in the review. All patients were initially alemtuzumab naïve. Mean baseline EDSS was 1.5-6.3. Three studies used myelo- and lympho-ablative BEAM-ATG conditioning; the others used lympho-ablative cyclophosphamide (50mg/kg/day for 3-5 days) with ATG (or alemtuzumab in a minority of patients). Both rabbit and horse ATG were used with dosing between 2.5-10mg/kg/day for 2 days or 0.5-1.5mg/kg/day for 5 days.

The available data showed a mean EDSS reduction from a baseline of 3.89 (3sf) to 2.96 at five-year follow-up.

Studies with lower pre-aHSCT EDSS experienced the greatest reduction in EDSS. Event-free survival (EFS) to five years was variable between studies ranging from 0% if high pre-aHSCT EDSS, to 85% if low EDSS pre-aHSCT. Studies with the lowest initial EDSS experienced higher progression-free survival (PFS) to five years, around 90%.

All-cause mortality across the studies was 2.6%; treatment related mortality (TRM) was 0.7%.

The percentage of patients retained in the studies after five years stood at only 28.9% compared to the alemtuzumab arm where retention stood at 83.0% (p< 0.001). Comparison of EDSS at five-year follow-up between the two study arms may therefore be misleading due to survivorship bias in the aHSCT arm.

Alemtuzumab.

A total of 39 studies met the search criteria. After application of eligibility criteria and removal of duplicate data, three studies included 759 patients treated with alemtuzumab: CAM MS223, CARE-MSII, and CARE-MSI, were used in the study. Both CAM MS223 and CARE-MSI included treatment naïve patients; CARE-MSII (357 patients) included previously DMT exposed patients.

Mean EDSS pre-alemtuzumab was 1.9-2.7; only 6 patients had an EDSS >5.0. Peak post-alemtuzumab EDSS reduction occurred at 2 years with the CAM MS223 study; the best mean EDSS reduction was 0.3. The improvements at two years were negated by five years.

Mean EDSS across the studies progressed from a baseline of 2.31 (3sf) to 2.34 at five-year follow-up representing a mean increase of 0.03.

All-cause mortality across studies was 0.5%; TRM was 0.1%.

Conclusions: While it is imperfect to indirectly compare treatments from different studies, EDSS outcome patterns between aHSCT and alemtuzumab differed remarkably. aHSCT, in contrast to alemtuzumab, was associated with the largest magnitude of fall in EDSS that was sustained in the long-term to five years. A direct comparison of aHSCT with alemtuzumab in a RCT seems warranted to confirm these observations of long-term benefit with aHSCT.

[Mean change in EDSS post-HSCT or alemtuzumab]

Disclosure: Nothing to declare.

Careggi University Hospital, Florence, Italy

Background: In the last 20 years, high dose chemotherapy with autologous hematopoietic stem cell transplantation (aHSCT) has emerged as an effective and safe treatment for aggressive forms of multiple sclerosis (MS). Nevertheless, no data have been published about reconstitution of either natural or vaccination-driven immunity after aHSCT and the consequent indication to re-vaccinate patients. We report an updated analysis of antigen-specific immune recovery in a series of MS patients after aHSCT, having increased the subset of patients included in the study.

Methods: Blood samples from 32 MS patients who underwent aHSCT in our Center between 2006 and 2017 were analyzed. Each patient underwent mobilization with cyclophosphamide (CTX) 4gr/sqm + GCS- F and was conditioned with BEAM/ATG regimen. Antibody titres for varicella-zoster, measles, rubella, and hepatitis B viruses were analysed before mobilization (baseline) and at 6 months, 1 year and then yearly after aHSCT. Chemiluminescent Microparticle Immunoassays (CMIA) were performed to determine Rubella and hepatitis B surface antigen antibodies (anti-HBsAg). Chemiluminescent Immunoassays (CLIA) were performed to assess Varicella Zoster and Measles. All patients received prophylaxis with acyclovir and Thrimethoprim-Sulphametoxazole for six months after aHSCT. Patients did not receive any re-vaccinations in the follow-up period.

Results: All patients showed a complete and sustained engraftment: median (range) time to PMN≥0.5x10⁹/L and platelets≥20x10⁹/L were 12(9-15) and 11(7-14) days, respectively. Patients showed also a complete return to a normal lymphocyte subset counts within two years from transplant. No case of measles, rubella, or chickenpox occurred after transplant, with a median follow-up of 40 (17-124) months. Table 1 reports the number of patients with positive or negative antibodies titres at baseline, 6 months and 2 years after aHSCT, respectively. A loss of serum protective immunity was observed in a variable rate of patients with all the tested agents: 14% in measles, 16% in rubella, 20% in hepatitis B, and 7% in Varicella Zoster.

Conclusions: Re-vaccination in patients who underwent an autologous HSCT for a severe autoimmune disease is a common practice in many centers and is also recommended in the EBMT guidelines. However, some concerns about this practice were raised for the putative role of vaccinations as an autoimmunity trigger. In the literature there is no study on the loss of protective antibody titer in either natural or vaccination-driven immunity with regards to patients transplanted for autoimmune diseases. In our series a high variability in antibodies titers at baseline was shown. The larger subset analysed confirms that most patients showing a protective titre against the tested agents, show a trend to maintaining it. A possible approach might be to revaccinate the patients with unprotective titre at 2 years after HSCT, taking into account the individual risk of being exposed to the infection; a larger series of data is necessary to provide conclusive evidences on this topic.

Disclosure: No disclosures

University Hospital Zurich, Zurich, Switzerland

Background: Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disease of the CNS and the leading cause of non-traumatic neurological disability of young adults. Inflammatory forms of MS respond to immunomodulation with disease modifying treatments (DMTs), but some subgroups of patients continue to have clinical and/or MRI disease activity despite DMTs. There is increasing evidence, including randomized controlled trials, that demonstrates robust clinical efficacy of high-dose chemotherapy (HDCTx) with autologous stem cell rescue (ASCT) in patients with highly active MS.

Methods: In 07/2018 the Swiss Federal Office of Public Health approved the treatment of MS patients with HDCTx+ASCT at our single center (University Hospital Zurich). To be eligible for reimbursement (i) patients must have inflammatory breakthrough activity of MS despite highly effective DMT; (ii) the indication needs to be confirmed by our interdisciplinary hemato-neuroimmunological board; (iii) patients are required to participate in a registry study for 5 years post-ASCT. Patients are mobilized with 2 days of cyclophosphamide 2g/m² and Filgrastim. HDCTx comprises BEAM (BCNU, etoposide, cytarabine, melphalan) and ATG 3.75 mg/kg on d+1 and +2 post stem cell infusion.

Results: So far 20 patients (10 females, 10 males) with a mean age of 40.6 years (+7.5y) and disease duration of 8.4 years (+4.4y) were enrolled into the registry. On the “Expanded Disability Status Scale” (EDSS) patients had a mean score of 5.0 (+1.2). 6/20 (30%) patients had relapsing remitting MS (RRMS), 7/20 (35%) had secondary progressive (SPMS) and primary progressive (PPMS) disease, respectively. The indication for HDCTx+ASCT was clinical progression in 14/20 patients (70%), clinical disease activity in the form of relapses in 5 (25%), and/or radiological activity (new or contrast-enhancing lesions) in 7 patients (35%). Last treatments prior to ASCT were fingolimod (15%), rituximab (40%), ocrelizumab (30%), or natalizumab (15%).

Overall, treatment was tolerated well, although the majority of patients developed adverse events (AE). Most common AEs were oral mucositis/pharyngitis and/or enteritis in 18/20 patients. Upper airway and urinary tract infections were each observed in 4 patients, respectively. CMV reactivations occurred in 4/20 patients and were severe in 2 (including CMV enteritis and hospitalization for intravenous antiviral therapy). HSV reactivations (n=2) and BK cystitis (n=2) were also observed. A total of 9 serious AEs were recorded (CMV n=2; hemorrhagic cystitis, gastroenteritis with ileus, laryngitis, cervical abscess (post mobilization, prior to ASCT), pulmonary embolus (several months post ASCT), gastrointestinal bleeding, manic episode). Six patients experienced transient neurological deterioration. Other AEs were hypotension (n=3), cholecystolithiasis (n=1), and epistaxis (n=1). With the limitation of short follow-up, a substantial proportion of patients reported improvements of neurological functions and less fatigue, however, longer observation periods are needed to evaluate the potential benefits of this intensive treatment.

Conclusions: Here, we report on the establishment of a national registry program for MS patients undergoing ASCT. The fast recruitment indicates an unmet need for a subgroup of young patients with aggressive, conventional DMT-refractory MS. The safety profile is acceptable from a transplanter’s perspective - however, bacterial and viral infections are common and require particular attention and prophylactic care.

Clinical Trial Registry: BASEC-number: 2018-01854 (Data and Biomaterial Collection for the Evaluation of Autologous Hematopoietic Stem Cell Transplantation in Relapsing Remitting and Progressive Multiple Sclerosis Patients (Registry))

Disclosure: Nothing to declare.

University of São Paulo, Ribeirão Preto, Brazil

Background: Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular damage, deregulation of the immune system and fibrosis of the skin and internal organs. The injury and apoptosis of microvascular endothelial cells are indicated as initial events of the disease, leading to physiological changes in the endothelium and vasculopathy. Autologous Hematopoietic Stem Cell Transplantation (AHSCT) promotes resetting of the immune system and has emerged as a treatment option for patients with severe and progressive SSc. Although AHSCT leads to clinical improvement, the mechanistic effects are still not completely understood. In this study, we aimed to investigate if AHSCT modifies the expression of endothelial markers in skin biopsies.

Methods: Samples of skin from the forearms of 27 SSc patients were evaluated by immunohistochemistry (IHC) before and at 6 and 12 months after AHSCT. Biopsies were marked with anti-CD31, -VEGF, -VEGFR2, -ANGIOPOIETIN 1, -ANGIOPOIETIN 2, -TIE, -ENDOTHELIN-1, -CD105 and -VE-CADHERIN antibodies and stained with Hematoxylin and Eosin (HE) and Picrosirius Red. The images were analyzed by ImageJ software

Results: Most participants were female (78%) with a mean (standard deviation, SD) age of 36 (9.4) years. The mean (SD) time between diagnosis of disease and transplantation was 3.2 (3.1) years. Clinical evaluation of fibrosis assessed by Rodnan´s score improved at 6 and 12 months compared to baseline (p< 0.0001). Histological analysis of fibrosis evaluated by HE and picrosirius red showed reduction of skin thickness (p< 0.0001) and collagen density (p=0.0193) after AHSCT.

The only endothelial marker that decreased after AHSCT was ANG1 (p=0.0001). All the other evaluated markers did not change (p>0.05) after AHSCT, when compared to baseline. Except for ANG1, our results indicate that ASHCT does not modify the expression of endothelial markers, anti-CD31, -VEGF, -VEGFR2, -ANGIOPOIETIN 1, -ANGIOPOIETIN 2, -TIE, -ENDOTHELIN-1, -CD105 and -VE-CADHERIN.

Conclusions: Our study shows that AHSCT therapy is able to improve fibrosis by reducing skin thickness and collagen fiber density, as assessed by Rodnan’s score and by histopathological analysis, respectively. However, no changes in markers of endothelial damage were detected, except for ANG1, which is related to vessel stabilization. Our data suggest that AHSCT may affect disease pathogenesis differently, concerning fibrosis and vasculopathy. Our results suggest that AHSCT does not improve SSc-associated endothelial damage, indicating that additional therapies may be warranted to more effectively treat the endothelial injury. The decrease in Rodnan´s score may be more associated with improvement of fibrosis than to a beneficial effect on the microvascular compartment.

Disclosure: Nothing to declare.

¹Amsterdam UMC, Location VUmc, Amsterdam, Netherlands, ²Not Applicable, Manilla, Philippines, ³Erasmus MC, Rotterdam, Netherlands, ⁴Catharina Ziekenhuis, Eindhoven, Netherlands, ⁵Isala Ziekenhuis, Zwolle, Netherlands

Background: In the Netherlands, an unknown number of patients go abroad to fee for service clinics for stem cell transplantation for non-hematological diseases. In this IRB approved study, we gather information about patients that went abroad and how it affected their health care.

Methods: Patients going abroad for stem cell transplantation on their own initiative for any kind of disease were recruited through (social) media like Facebook communities and newspapers.

Patients were invited to contact the research team. To participants giving informed consent, a questionnaire was sent.

The survey consisted of 3 parts: one set of questions regarding the stem cell transplantation abroad. Additionally, two validated patient-reported outcomes were included: the EORTC30 and NeuroQoL54.

Results: To date out of 51 participating patients, 30 finished the survey. 91,4% underwent a stem cell transplantation for multiple sclerosis (MS), 2,9% for Lyme’s disease and 8,7% for other reasons

For the preliminary results presented here, we report on the first part of the questionnaire for 24 patients that had filled out the survey (before Dec. 2019) and received aHSCT treatment for MS.

A total of 24 people were included in this preliminary analysis (12 [50%] women; mean age, 46 [SD, 9.7]), 7 relapsing-remitting MS (RRMS, 7 secondary progressive MS (SPMS), 10 primary progressive MS (PPMS), (mean disease duration, 8 years [SD, 6.1], [Range 0-23]).

Most people were treated in Russia 10 [42%], Mexico 8 [33%], India 3 [13%]. The other three were treated elsewhere.

All except for one patient chose for their center based on “own research” or “success stories from other patients”. None of the patients were referred by their physician. In three cases, the participants were advised in their decision for a specific clinic by their neurologist.

None of the participants was treated as part of an RCT.

Thirteen participants arranged for follow-up visits with a hematologist, three were advised so by their neurologist. Five arranged these check-ups after their return. Six have not had any follow-up by GP or hematologist.

Sixteen participants did not feel supported by their treating physician in their decision.

The average cost was € 55000 [Range 27000-110000. Sixteen participants [67%] financed through crowdfunding. Others paid with their own means. In none of the cases, the health insurance contributed to financing the treatment. Aftercare was paid for by health insurance in 21 [87%] participants.

Conclusions: The decision to go abroad for HSCT for not supported indications is usually made by the patient, regardless of the advice of the treating physician. Many patients go abroad for SPMS and PPMS, whereas highly active RRMS is the only evidence-based indication. As a result, patients undergo high-risk treatment for non-evidence based indications (like progressive MS). Patients are easily lost to follow up, as they often arrange aftercare on their own. Central registration of people going abroad for this high-risk treatment could contribute to better safety with the ultimate goal to organize reimbursement for selected cases and attention to aftercare.

Clinical Trial Registry: Not applicable

Disclosure: nothing to declare.

Northwestern University, Chicago, IL, United States

Background: Multiple sclerosis (MS) afflicts 2.5 million people worldwide (400,000 in the United States), and is a chronic disease, second only to congestive heart failure in cost of health care for a chronic illness. Lifetime direct costs per patients are greater than 4 million dollars and disease modifying therapy (DMT) is approximately 75% of the direct costs. DMT cost $80,000.00 per year (with a few costing more). We reported that after hematopoietic stem cell transplantation (HSCT) for frequently relapsing MS, only 16% relapsed and needed to restart DMT after 5 years. We now evaluated cost/ charges for HSCT on 42 consecutive patients treated with a non-myeloablative cyclophosphamide (200 mg /kg) and rabbit antithymocyte (ATG) (6.0 mg/kg) regimen.

Methods: Peripheral blood stem cells were collected 10 days after intravenous cyclophosphamide (2 g/m2) and 5 to 10 µg/kg per day of subcutaneous filgrastim beginning 5 days after cyclophosphamide. The immune ablative regimen was intravenous cyclophosphamide, 50 mg/kg per day on days −5 to day −2 before stem cell infusion (day 0) and rabbit antithymocyte globulin, 0.5 mg/kg on day −5, 1.0 mg/kg on day −4, and 1.5 mg/kg on days −3, −2, and −1. Methylprednisolone (1000 mg) was infused 30 minutes prior to rabbit antithymocyte globulin infusion.

Charges included all tests including blood draws, MRI imaging, echocardiograms, electrocardiograms, and chest radiograph, and all treatments and interventions including pre-HSCT evaluation, hematopoietic stem cell mobilization and cryopreservation, inpatient transplant admission charges, and all medications, nursing care, and room charges. The only charges not captured were physician history and physical and physician progress notes. Analysis was separated into direct costs (costs directly related to patient care (e.g. medications, laboratory tests, transfusions, nursing care), indirect costs (cost necessary to operate a hospital but not directly related to patient care e.g. managers, supervisors, medical records, accounting, information systems, marketing, legal, malpractice insurance, building maintenance and depreciation, house-keeping), total cost (sum of direct and indirect), net revenue collected, and net income (profit).

Results: Mean direct costs were $42,295 (range $33, 887 to $57,704), mean indirect costs were $42,888 (range $33,653 to $62,555), and mean total costs were $85,184 (range ($70,635 to $120,260). Mean revenue collected was $95,268 (range $16,544 to $173,204) and mean net income (profit) per patient was $10,084.

Conclusions: The mean costs and charges of HSCT using this non-myeloablative regimen are equivalent to DMT charges for one year (approximately $80,000) but comparable DMT charges do not include physician, laboratory, imaging, or hospitalization fees, if any. Since after a one-time treatment with a non-myeloablative HSCT regimen, the majority of patients remain treatment-free beyond 5 years, non-myeloablative HSCT with a cyclophosphamide ATG regimen appears to be cost effective.

Clinical Trial Registry: None

Disclosure: Nothing to declare.

¹CHU de Poitiers, Poitiers, France, ²CHU de Poitiers, Poitiers, France, ³MATHEC, Hôpital Saint Louis, Paris, France, ⁴The Christie NHS Foundation Trust, Manchester, United Kingdom, ⁵University of Liverpool, Liverpool, United Kingdom, ⁶Heidelberg Hospital, Heidelberg, Germany, ⁷EBMT ADWP Office, Paris, France, ⁸IRCCS Ospedale Policlinico San Martino, Genova, Italy, ⁹St Vincents Hospital, Sydney, New South Wales, Sydney, Australia, ¹⁰University of New South Wales, Sydney, Australia, ¹¹St Vincent’s Hospital, Darlinghurst, Sydney, Australia, ¹²IRCCS Burlo Garofolo, Trieste, Italy., Trieste, Italy, ¹³Charité - University Medicine Berlin, Berlin, Germany, ¹⁴Sheffield Teaching Hospitals NHS Foundation, Sheffield, United Kingdom

Background: Behcet´s disease (BD) is a rare autoimmune disease mostly presenting with recurrent oral and genital aphthous ulcers, and uveitis. Other common symptoms include gastrointestinal, vascular, neurological and articular manifestations¹. Treatment is based on chronic immunosuppression with conventional disease modifying or targeted biologic drugs², although some refractory patients have been treated by autologous hematopoietic stem cell transplantation (AHSCT)³. This study aims to evaluate the outcome of AHSCT in adult patients with BD.

Methods: Adults who received AHSCT primarily for BD (according to International Classification Criteria) were identified retrospectively within the EBMT registry. Treating physicians were surveyed to produce a retrospective evaluation of outcomes. Complete Remission (CR) was defined as no evidence of disease activity and Partial Remission (PR) was defined as any documented clinical and/or laboratory response in patients that is less than CR.

Results: We retrospectively collected the data from 8 out of 9 cases reported to the EBMT registry and extracted data of 2 further patients from published literature⁴. Four were female, median age at onset of BD was 24 years (range 9-50). Median age at AHSCT was 32 years (27-51). Patients had received median 4 (2-12) prior lines of therapy: 89 % of the patients were treated with corticosteroids, and 50 % received either methotrexate, antiTNFa or cyclophosphamide. All had active disease before mobilization, which was performed with cyclophosphamide and G-CSF in 9 patients and G-CSF alone in 1 patient. Conditioning regimen was Melphalan 200mg/m² in 5 patients, BEAM in 3 patients, and Cyclophosphamide 200mg/kg plus antithymocyte-globulin (ATG) in 2 patients. Median follow-up was 48 months (range 6-120 months). No TRM was reported, three patients had infectious complications and a single patient had paroxysmal atrial fibrillation, line-associated deep venous thrombosis and depression. At 6 months, 6 patients were in PR with corticosteroid maintenance and 3 in CR without any further treatment. There was one relapse with pan-uveitis. One patient failed to respond to AHSCT and proceeded to rescue with allogeneic HSCT, but died five years post-transplant from chronic GvHD and CMV infection. Otherwise, no late complications in patients treated with AHSCT were reported.

Conclusions: AHSCT is feasible and safe in multi-refractory patients with BD. Although treatment-free CR was achieved in only 3 of 10 patients analyzed, AHSCT has the potential to stabilize BD in patients who fail to respond to conventional therapies. Further evidence, ideally from prospective studies, are warranted to determine whether AHSCT should be considered a standard of care in treatment-resistant BD.

Disclosure: No disclosure

Artemis Hospital, Gurugram, India

Background: Multiple Sclerosis (MS) is an autoimmune disease in which there is both B and T cell mediated destruction of the nervous system. Historically it was observed that Autologous Hematopoietic Stem Cell Transplant (HSCT) is safe and effective in achieving long term Disease Modifying Therapy (DMT) free survival. Initially myeloablative conditioning with BEAM-ATG (BICNU, Etoposide, Ara-C, Melphalan - Anti Thymocyte Globulin) was used, but the mortality rates were high, so the non-myeloablative conditioning with Cyclophosphamide-ATG (Cy-ATG) was used, showing almost same outcome and with low mortality rates.

Methods: Seventy one consecutive patients of MS who underwent AHSCT were prospectively enrolled at a single center tertiary hospital.

Results: A total of 71 patients were of MS with median age 48 years (range 25-67 years) and a total of 65 patients underwent AHSCT out of which 36 (51%) males were included. Six patients were rejected due to various reasons. The diagnosis of MS was confirmed by clinical evaluation, MRI, VEP and BERA. Of these, 36(51%) were SPMS, 22 (31%) were RRMS and 13(18%) were PPMS with a median EDSS score of 5 (range 1 - 8.5). the median time from diagnosis to AHSCT was 11 years (range 0 - 37 years). In majority of these patients; 53(81%) stem cell mobilization was done with G-CSF and in remaining either Cyclophosphamide + G-CSF 11(17%) or G-CSF + Plerixafor 2(3%) was used. Regimen related toxicity was seen in 9 patients in the form of anaphylaxis (5), hemorrhagic cystitis (3) and AKI (1). The median CD34 dose was 7.17 (range 2.82 - 13.84). The median time to neutrophil engraftment was 9 days (range 6 - 12 days) and platelet engraftment was 12 days (range 9 - 18 days). The median number of blood components transfused included RBC 2 units (range 0 - 7), RDPs [14 units (range 0 - 38) and SDPs 1 units (range 0 - 8). There was a significant improvement in the EDSS score [mean 5.07 SD 1.77 to mean 4.73 SD 2.09; p value < 0.001] till the discharge. There was only one death. Thirteen (20%) patients had transient worsening of MS related symptoms post-AHSCT which resolved completely before discharge. The most common type of infection was urinary (50%).

Conclusions: HSCT is a safe and effective treatment option in improving disability scores in patients of MS with refractoriness to DMTs. Our study showed that HSCT is well tolerated treatment option in MS with acceptable mortality of 1-2 %. However, long term follow up is needed to look for the response.

Disclosure: Nothing to declare.

¹Saint Antoine Hospital, INSERM UMR 938, Sorbonne University, Paris, France, ²Saint Antoine Hospital, Paris, France, ³University Hospital Tuebingen, Tuebingen, Germany, ⁴Hôpital Saint-Louis, Paris, France, ⁵Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom, ⁶University of São Paulo, Ribeirão Preto, Brazil, ⁷AP-HP, Hôpital Avicenne, Paris 13 University Bobigny, France, ⁸Charité - Universtiy Medicine Berlin, Berlin, Germany,

Background: Takayasu arteritis (TAK) is a chronic granulomatous large-vessel vasculitis, commonly affecting young women, characterized by arterial thickening and fibrosis leading to stenosis and vascular occlusions. More than 10% of patients are refractory to conventional immunosuppressive disease-modifying drug (DMARD) therapy and are at high risk for vascular complications. Autologous hematopoietic stem cell transplantation (AHSCT) has emerged as a promising treatment option in severely affected and refractory patients with various autoimmune diseases. Several case-reports and small case series demonstrated the potential efficacy and safety of AHSCT for systemic vasculitis, particularly ANCA-positive vasculitis and Behçet’s disease. This study, approved by the ADWP, aims to evaluate the use and outcome of AHSCT in adult TAK patients.

Methods: This is a retrospective survey of patients reported to the EBMT data management between 1998 and 2018, who received AHSCT primarily for TAK. A specifically designed questionnaire was sent to each referring transplant centre to obtain all relevant clinical and laboratory data. Remission was defined as no evidence of inflammation or worsening of vessel disease.

Results: Data from six adult patients treated with AHSCT between 2003 and 2018 for refractory Takayasu have been identified. Median (range) follow-up was 9.9 (1-14) years. Five patients were female (83%), median age was 25 (9-39) years at diagnosis and 28 (22-41) years at AHSCT. All patients were pretreated with a median of 6 (4-8) lines of therapy, including systemic corticosteroids (in 6 patients), methotrexate (5 patients), cyclophosphamide, mycophenolate mofetil or infliximab (4 patients), tocilizumab or etanercept (2 patients), and other biologic or conventional-synthetic DMARDs. Mobilization was performed with cyclophosphamide 2g/m² (4 patients) or 4g/m² (2 patients) in combination with granulocyte-colony stimulating factor (G-CSF). The graft was CD34 positive selected in 2 cases. Conditioning included cyclophosphamide 200 mg/kg in 5 patients, and cyclophosphamide 120 mg/kg plus fludarabine 90 mg/m2 in one patient. All patients received rabbit anti-thymocyte globulin. After AHSCT, 4 patients received G-CSF during a median of 5 (5-6) days. A median of 3.9 (2-4.20) x 10˟6 CD34+cells /per kilogram were reinfused. Engraftment, defined as neutrophils ³0.5 x10^9/L and platelet ³20 x10^9/L were detected at a median of 8 (5-13) and 8 (5-11) days, respectively. All patients had active disease before AHSCT. At six months post-transplantation, remission was obtained in all cases, which persisted at 12 months in 5 cases. Four patients reactivated TAK at a median time of 27 (7-52) months after AHSCT, and 3 resumed disease-modifying therapy. During follow-up none of the patients developed secondary malignancy and one patient had a miscarriage. At last follow-up, all patients were alive, 2 patients were in remission (off-therapy), 2 patients improved compared to baseline, and 2 patients were in complete and partial remission, respectively, under immunosuppressive treatment.

Conclusions: This small retrospective series demonstrates that AHSCT has the potential to provide significant clinical responses in TAK patients who had been unresponsive to previous immunosuppressive therapy, with an acceptable safety profile. Therefore, AHSCT may be considered as a ‘clinical option’ for patients with severe, treatment-resistant and poor-prognosis TAK, ideally before the development of compromised vital organ function.

Clinical Trial Registry: na

Disclosure: JAS declare.s speaker fees at educational events supported by Sanofi, Janssen, Jazz, Mallinckrodt and Gilead

¹University of Sheffield, Sheffield, United Kingdom, ²Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom

Background: Disease modifying therapies (DMT) for RRMS have been the mainstay of treatment for 20 years. Alemtuzumab is one of the most highly efficacious DMT for RRMS. However some patients continue to experience disease activity despite adequate Alemtuzumab therapy. AHSCT has been used with increasing frequency over the last decade to treat very active RRMS despite the use of DMTs. However efficacy and timing of delivering treatment in patients who failed Alemtuzumab remains unclear. Here we report a case series of patients with RRMS who received AHSCT after failing to respond to Alemtuzumab treatment.

Methods: A case series of all patients who received AHSCT for RRMS after failing to respond to a full course of Alemtuzumab was compiled. Details of 4 cases were collected from a national referral centre in the north of England. Clinical details, MRI changes, efficacy and safety data related to the use of Alemtuzumab and AHSCT were recorded. AHSCT was performed using a standard Cyclophosphamide / ATG mobilization and conditioning regime.

Results: All patients experienced clinical and radiological evidence of disease activity and progression whilst on Alemtuzumab. The mean treatment period with Alemtuzumab was 27 months (SD 23.2 months). Mean treatment courses was 2.5. Mean follow up after AHSCT was 48.5 months (SD 32.7). No patient experienced further relapses or MRI disease activity following AHSCT. EDSS scores improved in all patients following AHSCT (mean 1.12 points, SD 0.62). Patients experienced routine grade 1-3 complications during transplantation period. No autoimmune complications were recorded.

Conclusions: Our data suggests that AHSCT use is effective and safe in patients who failed to respond to Alemtuzumab.

Clinical Trial Registry: No Applicable

Disclosure: John Snowden declare.s speaker fees at educational events supported by Sanofi, Janssen, Jazz, Mallinckrodt and Gilead.

¹FOSCAL, Bucaramanga, Colombia, ²Universidad Autónoma de Bucaramanga, Bucaramanga, Colombia, ³Clínica de Marly, Bogotá, Colombia, ⁴Centro Médico Imbanaco, Cali, Colombia

Background: Autologous hematopoietic stem cell transplantation (aHSCT) is a promising therapeutic modality for severe autoimmune diseases, especially as a treatment option for systemic sclerosis (SS). The aim of this study was to describe clinical experience in the use of aHSCT for SS in three centers in Colombia.

Methods: We conducted an observational study of adult patients diagnosed with SS and treated with aHSCT at centers from three different cities of Colombia from 2010 to 2019. Patients with SS were autografted in the centers with peripheral blood stem cells. The autografts were performed after conditioning with cyclophosphamide and BEAM chemotherapy. Laboratory results and complications after aHSCT were evaluated. Patients were follow-up to 3 years.

Results: Information from 13 patients were collected from the three centers. Median age was 44 years (27-53). We included 11 females (85%) and 2 males (15%). As a first-line treatment, 11 patients (84,6%) were treated with steroids. Median dose for cyclophosphamide at mobilization was 2,3 mg/m2 (2-3,5 mg/m2). About conditioning treatment, cyclophosphamide was performed in 12 patients (92,3%), while BEAM chemotherapy was performed in 1 patient (7,7%). The total number of viable CD34+ infused cells ranged between 3,1-25,57x10⁶ (average 8,1). Patients recovered ≥0.5x10⁹/L absolute granulocytes by day 14 (8-43 days), and platelet values were also ≥20x10⁹/L by day 14 (6-43 days). Febrile neutropenia presented in 4 patients (30,7%), mucositis in 2 patients (15,3%), Pneumocystis jiroveci Pneumonia in 4 patients (30,7%) and 1 patient presented cytomegalovirus reactivation (7,7%). Only 1 patient (7,7%) presented cardiovascular complications and another patient (7,7%) presented endocrine complications. To date, there have been no deaths attributable to the transplant, yielding a 3 years overall survival of 100% and progression-free survival was 92,3% for all the patients.

Conclusions: AHSCT reduces the risk of all-cause mortality and has properties of a disease-modifying antirheumatic treatment in SS patients, leading to a high overall survival time. AHSCT should be proposed for carefully selected patients with refractory SS, therefore, optimal patient selection, pre-transplantation workup and posttransplant management need to be stablished.

Disclosure: Nothing to declare.

Northwestern University, Chicago, IL, United States

Background: Autologous hematopoietic stem cell transplantation (HSCT) induces remission of refractory Crohn disease (CD) but approximately 50% and 80% relapse and restart standard therapies at 3 and 5 years, respectively, post HSCT. We, therefore, undertook a pilot study of allogeneic HSCT using either matched sibling donor or umbilical cord blood (UCB), if a matched donor was not available.

Methods: Eligible patients were 18 to 45 years old, had an established diagnosis of Crohn disease, failed corticosteroids, 5-aminosalicylate, and at least two anti-TNF (infliximab, adalimumab, or certolizumab) drugs with a Crohn disease activity index (CDAI) between 250 to 400 or Craig Severity Score (CSS) > 17. Donor preference was given for unmanipulated healthy adult HLA 6 / 6 matched sibling, followed by unrelated 6/6 matched UCB and then unrelated 5/6 matched UCB. When available two UCB units were infused. The conditioning regimen was dose escalated during the protocol’s duration in an attempt to maximize donor engraftment. Conditioning drugs were: 1) cyclophosphamide 200 mg/kg divided as 50 mg /kg on days -5,-4,-3 and -2, 2) fludarabine (75 to 150 mg / m2) divided as 25- 30 mg /m² /day (between days -7 to -3), and alemtuzumab (60 mg to 90 mg) divided 30 mg day (between days -3 to -1). Cyclosporine (100 mg po bid) or tacrolimus (1.0 mg bid) was initiated on day -2 and continued for 9 months.

Results: Average time of hospital engraftment and hospital discharge was day 13 and 14, respectively, with no difference in mean day of engraftment or discharge between matched sibling versus UCB transplantation. The mean number of red blood cell and platelet transfusions were both 3.4. Neutropenic infections included one case each of diarrhea due to clostridium difficile, and blood cultures positive for Escherichia coli, Enterococcus faecalis, and extended broad spectrum beta-lactamase producing Escherichia coli. Late post discharge events were tacrolimus-induced chronic renal failure mandating renal transplantation in a patient with a history of pre-transplant tacrolimus induced acute renal failure, surgery for colonic stricture without evidence of active Crohn disease that was complicated by bowel perforation and pseudomonas sepsis, and one death 3 months post HSCT from disseminated adenovirus infection. Following the patient’s death enrollment was terminated. There was no acute GVHD and one case of possible limited chronic GVHD.

Despite no evidence of donor engraftment, all patients entered and maintained without treatment a clinical remission (CDAI < 150), MRI imaging remission, endoscopic and histologic remission for the 5 years of study follow-up.

Conclusions: Complete treatment-free 5-year remissions without donor engraftment suggests that the conditioning regimen and nine months of maintenance tacrolimus, not the allogeneic hematopoietic stem cells, were responsible for remission. Alternatively, the infused donor graft may have provided a non-CD3+, non-CD33+ non-hematopoietic type of stem cell such as donor mesenchymal stem cells that in theory could facilitate a durable remission

Clinical Trial Registry: FDA IND 16908, www.clinicaltrials.gov NCT 01288053

Disclosure: Nothing to declare.

CAR-based Cellular Therapy – clinical

¹Royal Marsden Hospital, Sutton, United Kingdom, ²The Institute of Cancer Research,, London, United Kingdom, ³University College London Hospitals, London, United Kingdom, ⁴University Hospitals Bristol NHS Foundation Trust, Bristol, United Kingdom, ⁵Patient Representative, NCCP ALL Panel, United Kingdom, ⁶Great Ormond Street Hospital, London, United Kingdom, ⁷Royal Manchester Children’s Hospital, Manchester, United Kingdom, ⁸Queen Elizabeth Hospital, Birmingham, United Kingdom, ⁹Newcastle Upon Tyne NHS Foundation Trust, Newcastle upon Tyne, United Kingdom, ¹⁰Christie NHS Foundation Trust, Manchester, United Kingdom, ¹¹Manchester University NHS Foundation Trust, Manchester, United Kingdom, ¹²Kings College Hospital NHS Foundation Trust, London, United Kingdom, ¹³Cancer Drugs Fund, NHS England, London, United Kingdom, ¹⁴Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom

Background: Following European Medicines Agency (EMA) approval of Tisagenlecleucel (KYMRIAH^®) for the treatment of relapsed/refractory acute lymphoblastic leukaemia (ALL) in children and young adults in 2018, England established a structured funding programme via the National Health Service England (NHSE) Cancer Drugs Fund.

Methods: NHSE established a national CAR-T clinical panel for ALL (NCCP ALL). The aim of the NCCP ALL was to review cases to confirm eligibility against published criteria in line with the ELIANA study inclusion criteria and ensure prompt national access to Tisagenlecleucel. All CAR-T centres (3 open at NCCP set up and 9 open at 1 year review) were accredited for the Immune Effector Cell Standards in the 7^th edition of the JACIE Standards in line with EBMT/JACIE recommendations (Yakoub-Agha et al 2019). The NCCP ALL consisted of representatives from NHSE, CAR-T centres, patient representation and independent ALL clinical experts. We describe panel experience over a one year period.

Results: The NCCP met by weekly teleconference to review cases referred by individual CAR-T centre lead clinicians who endorsed eligibility. Approval for access to Tisagenlecleucel was granted through unanimous panel consensus agreement following review of eligibility criteria (according to disease and CD19+ status, absence of CNS disease, performance status and organ function). Allocation to centre was achieved by review of geography, slot availability and patient preference.

From 19.11.2018-18.11.2019 34 patients were approved (age range 9 months - 21 years, median age 10.5 years). 5 did not proceed to leukapheresis (2 incorrect diagnosis of relapse, 1 received alternative CAR-T clinical trial product, 2 unable to proceed due to disease progression/complications). At time of abstract submission 23/29 (79.3%) patients had undergone CAR-T infusion. 3 patients who underwent leukapheresis were unable to proceed to infusion (1 patient due to emergence of CD19 negative disease, 1 patient due to CNS disease progression, 1 patient received cranial radiotherapy to control CNS disease and suffered frank bone marrow relapse treated with Inotuzumab followed by a failed manufacture). 3 patients await infusion. Mean time from panel approval to leukapheresis was 15 days (range 0-47 days) and mean time from leukapheresis to CAR-T infusion for patients infused was 64 days (range 35 - 92 days) Of 15 patients evaluable beyond 100 days (8 patients yet to reach this time point), 11 have a documented status of ‘alive in MRD negative remission’. This represents 73% patients infused (11/15). Brief toxicity and follow up data will be reported at EBMT 2020 with future planned efficacy analysis.

Conclusions: The establishment of a national panel in England for Tisagenlecleucel approval has allowed prompt, equitable and trackable access to this CAR-T product for ALL. From a worldwide perspective, NHSE is one of the first health services to introduce a national co-ordinated access programme of care and will utilise programme data to assess real world outcomes for patients treated with Tisagenlecleucel.

Disclosure: Nothing to declare.

King’s College Hospital NHS Foundation Trust, London, United Kingdom

Background: Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are the main toxicities complicating CAR T-cell therapy. High dose steroids are the current standard of care, though there remains a clinical need for patients that are refractory to front line treatment. Animal models have supported cytokine targeting therapies that can cross the blood brain barrier such as the IL-1 receptor antagonist anakinra. We report our experience with ICANS in a cohort of patients receiving CD19 CAR T-cells, including the first series of patients treated with anakinra for ICANS.

Methods: Patients with relapsed/refractory B cell non-Hodgkin lymphoma received axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisagen) between Jan 2019 and September 2019. Eligibility was determined independently by a panel of clinical experts from NHS England and data collected prospectively. ICANS was graded according to ASTCT Consensus Grading.

Results: A total of 43 patients received treatment (14 transformed FL, 2 PMBCL and 27 DLBCL): 38 received axi-cel and 5 tisagen. 14 of 43 patients (33%) experienced any grade of neurotoxicity, with 7 of 43 (16%) grade 3 or 4, lower than the rate reported in previous trials and real-world data. The most common clinical features were disorientation or confusion, dyspraxia and expressive dysphasia (n=9). Intensive care admission was required for 8 patients, with 3 requiring intubation.

Neuroimaging was performed in 13 patients: five patients with CT brain, five with CT and MRI brain, and three MRI. The only clear acute change was bilateral hippocampal enhancement for one patient on MRI, subsequently attributed to viral encephalitis. Lumbar puncture was performed in six patients: glucose and cytology was normal, with a mild rise in CSF protein (mean 0.96g/L, range 0.25-0.45g/L). One patient was diagnosed with HHV6 encephalitis. EEG was performed in 12 patients, with almost all (92%) displaying encephalopathic features (generalised rhythmic delta activity) and 2 (17%) with epileptiform foci over the left fronto-temporal region. No periodic discharges or seizures were captured.

High dose steroids (dexamethasone up to 40mg daily) was started for 11 patients for treatment of ICANS; all patients had received tocilizumab for prior or concurrent CRS. Anakinra was administered to five patients concurrently with steroids for ICANS that was high grade or not responsive to initial therapy with dexamethasone. The ICANS grade for these five patients at time of treatment was grade 3 for two patients, and grade 4 for three patients. Anakinra was given as 200mg daily subcutaneously, started at a median of 3 days (range 1 to 5) after the commencement of dexamethasone for ICANS treatment, and median number of 5.4 doses given (range 3 to 8). ICANS resolved in all patients surviving to day 30 (n=13), with persistent neurological features in one patient likely sequelae of viral encephalitis and one treatment related death (sepsis).

Conclusions: We describe the clinical features of ICANS in our real-world cohort of patients receiving standard of care CD19 CAR T-cells, and demonstrate the feasibility of anakinra in combination with dexamethasone for treatment ICANS that is severe or not initially responsive to high dose steroids.

Disclosure: Nothing relevant to declare.

¹University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Background: Chimeric-antigen-receptor (CAR-) T cells have demonstrated remarkable efficacy in the treatment of B-cell hematological malignancies, leading to the recent approval of two CD19-CAR-T cell products (Tisagenlecleucel/Kymriah and Axicabtagene ciloleucel/Axi-cel/Yescarta) in the US and Europe. CAR-T cell engraftment and expansion represent crucial parameters for efficacy of treatment. Monitoring of CAR-T cell concentrations has however been limited by the lack of diagnostic assays.

Methods: We performed prospective serial measurements of CAR-T cell levels in blood and body fluids of 18 patients treated with Axi-cel. Informed consent was obtained from all patients and the study approved by the ethics committee. Per protocol, blood samples are collected on days 0, 3, 7, 10, 14, 21, 28, 35, 56, 84, 180 and 365 after CAR-T cell infusion. In case of ICANS and lumbar puncture, cerebrospinal fluid (CSF) is also analyzed for CAR-T cell numbers. Quantification of CAR-T cells was performed using a newly developed digital PCR assay (Fehse et al., EBMT 2020).

Results: We have treated 18 patients with diffuse large B cell lymphoma with Axi-Cel. Sixteen of these patients were evaluable for day 30 response at time of abstract submission. CAR-T cells could be detected in the blood of all 16 patients, expansion and contraction followed the expected kinetics with median peak value of 11.2 CAR-T cells on (median) day 11.5 after infusion. Clinically, we observed only 2 responses (1PR, 1 CR) in 7 patients who had poor expansion of CAR-T cells (defined as peak numbers below and peak time-points above median), while 9 out of 10 patients with comparatively good expansion showed response (5 CR, 4 PR) on day 30. Seven out of 10 patients with good expansion experienced CRS and/or ICANS whereas only 2 of 7 patients with poor expansion had CRS or ICANS. CSF was collected from 3 patients with ICANS. In all 3 cases, high concentrations of CAR-T cells were detected in CSF. Two patients received dexamethasone for the treatment of ICANS. In both cases, treatment with dexamethasone (1 dose and 6 doses of 10mg respectively) led to a drop in the concentration of CAR-T cells, followed by recovery after discontinuation of dexamethasone (Figure 1). Data on more patients and cytopenias will be presented at the meeting.

Conclusions: Despite the relatively small patient number, our data emphasize the importance of monitoring CAR-T concentrations after infusion and indicate an association with response and side effects. CAR-T cell proliferation appears to bounce back after treatment with dexamethasone.

[Figure 1]

Disclosure: FA has received honorarium from Kite/Gilead for advisory board. NK has received honorarium from Kite/Gilead for advisory board. The dPCR assay used in this work has been made available as an “Expert Design Assay” based on agreement with Bio-Rad. BF, AB, CB, and KR would profit from potential future commercialization of the assay.

¹CHU de Lille, Université de Lille, Lille, France, ²LIRIC, INSERM U995, Lille, France

Background: We report the efficacy and tolerance of nivolumab (Nivo) in patients who did not achieve a complete response (CR) at one month after Yescarta^TM infusion.

Methods: Thirty-two patients with R/R DLBCL (13 male/19 female) were candidate for Yescarta^TM and underwent leukapheresis between November 2018 and December 2019 in our center. As of December 15, 2019, 29 were infused, 2 patients are waiting to be infused and one patient never got infused because CAR T-cell production failed twice. Twenty-five patients are evaluable for response at one month post CAR T infusion since one patient died at day 21 of septic shock. Median follow-up was 152 days (range, 39-354 days).

Results: Response rates according to IWC 2014 (Cheson 2014) at one month after CAR T-cell infusion were CR (n=11; 42%), partial response (PR) (n=5, 19%), stable disease (SD) (n=3: 12%), progressive disease (PD) (n=6; 23%). One patient with PR converted to CR two months after CAR T-cell infusion without subsequent treatment. All patients who achieved CR are alive and received no further treatment. All but 4 of the 13 patients who did not achieve CR received salvage therapy with Nivo. The 9 patients (3 PR, 3 SD and 3 PD) received Nivo at the dose of 240 mg/2 weeks. All patients received prophylaxis with valaciclovir and cotrimoxazole. Median time of the onset of Nivo was 60 days (range, 37-144 days) after CAR T-cell infusion. Median number of Nivo injections was 5 (range, 2-9). Two out of the 3 patients with PR achieved CR 60 days after initiation of Nivo. One of them subsequently received allogeneic hematopoietic cell transplantation and one is still receiving Nivo. In this latter patient, circulating CAR T-cells, mainly CD8⁺, dramatically increased following Nivo administration. One out of the 3 patients with PD experienced PR 60 days after Nivo. The 6 remaining patients with PR, SD and PD progressed after Nivo, of whom 2 died at day 90 and 173 after initiation of Nivo. Table 1 depicts outcomes of all patients who received Nivo. Three patients developed grade 2 bacterial pneumonia and one patient who received subsequent allo-HCT developed grade 1 psoriasis that was probably linked to Nivo. Overall, response to Nivo was recorded as CR (n=2, 22%) and PR (n=1, 11%). Six patients (67%) progressed.

Conclusions: Nivo seemed to be effective and safe in a small number of patients who did not achieve CR after CAR T-cell therapy.

Disclosure: Nothing to declare.

¹The First Affiliated Hospital, Zhejiang University, Hangzhou, China,²Zhejiang Province Engineering Laboratory for Stem Cell and Immunity Therapy, Hangzhou, China, ³Institute of Hematology, Zhejiang University, Hangzhou, China, ⁴Chaim Sheba Medical Center, Tel Hashomer, Israel, Tel Hashomer, Israel

Background: CAR-T therapy has become an ultimately effective solution for relapse or refractory (r/r) DLBCL. Therefore, after successful CAR-T therapy, patients are carefully monitored by positron emission tomography-computed tomography (PET-CT) instead of other treatment. Besides high cost, risk of ionizing radiation also limit the use of PET-CT in surveillance follow-up DLBCL. CtDNA derives from disrupted tumor cells preserving the characteristic of alteration in tumor genome. With the application of next generation sequencing (NGS), analysis large-scale sample of DNA become cheaper and faster showing great potential prospect in “liquid biopsy” avoiding the risk of failure of biopsy, surveillance of MRD in lymphoma, and observation of lymphoma subclone evolvement with early precise intervention.

Methods: We retrospectively collected clinical data, tumor sample preserved in formalin fixed paraffin-embedded tissue or liquid nitrogen storage and serum preserved in liquid nitrogen storage from the prospective clinical study aiming to evaluate the safety and efficacy of anti-CD19 CAR-T for r/r B cell lymphoma (ChiCTR-OCC-15007008). We profiled genome aberration with NGS in the baseline, relapsed, and progressive tumor sample after CAR-T therapy and ctDNA in baseline serum and reviewing serum in accordance with reviewing PET-CT scan. 8 DLBCL patients received CAR-T therapy between December 2016 and November 2017 were included in this analysis.

Results: The baseline characteristics are listed in table. The median follow-up is 322.5 days. 4 (50%) patients achieved complete response (CR), 1 (12.5%) patient achieved partial response and the rest of 3 (37.5%) patients showed no response 1 month after CAR-T therapy. 3 of 5 patients who achieved response relapsed within 4 months after CAR-T therapy while the rest of 2 patients remain CR for more than 20 and 27 months respectively.(Figure A) Grade 1, 2, and 3 cytokine release syndrome occurred in 2, 1, and 3 patients respectively. 89 and 446 hotspot genes NGS were performed in 1 and 7 patients respectively. Compared to PET-CT scan, the sensitivity and specificity of ctDNA profiling in detecting MRD is 94% and 64% respectively. Among 3 patients who relapsed from CAR-T, positive posttreatment ctDNA detection preceded PET-CT progression in patient 6 by 1.4 months (Figure B). The median number of abnormal genes in baseline tumor tissue is 4 and 15.5 (P=0.012) in the patients remained long-term CR and the patients failed from CAR-T therapy respectively. XPO1 E571K mutation was observed in 3 of 6 patients failed from CAR-T therapy.

Conclusions: CtDNA profiling is a promising new technique for surveillance of MRD in DLBCL after CAR-T therapy. In some cases, ctDNA can predict the disease progression earlier than PET-CT scan. A much number of abnormal genes in baseline particularly XPO1 E571K mutation may be a poor prognostic factor after CAR-T therapy in DLBCL.

[Baseline characteristics]

[Figure 1A. | Figure 1B. Positive posttreatment ct]

Clinical Trial Registry: ChiCTR-OCC-15007008

http://www.chictr.org.cn/

Disclosure: Nothing to declare.

University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Background: Adoptive immunotherapy with CD19-specific CAR-T cells has shown excellent efficacy in late-stage relapsed/refractory B-cell cancers leading to the recent approval of two CD19-CAR-T cell products. Being ‘living drugs’, the in-vivo expansion, migration, contraction and persistence of CAR-T cells after infusion are important variables most probably impacting both disease response and treatment toxicity. Remarkably, widely available diagnostic tools to rapidly assess CAR-T-cell ‘drug levels’ in the clinical setting are largely missing. Digital PCR (dPCR) represents an advancement of quantitative PCR and is characterised by excellent sensitivity, specificity, and reproducibility making it an ideal tool for real-time diagnostics of rare events. Here we aimed at developing and evaluating a novel dPCR assay for detection and quantification of Axi-cel CAR-T cells in vivo.

Methods: To establish a CAR-specific dPCR assay, we first cloned and sequenced the complete cDNA of the Axi-cel vector construct. We designed different combinations of primers and dual-labelled hydrolysis probes, each amplicon spanning at least two different regions of the CAR vector. Three combinations of primers (A, B, C) were successfully tested on CAR-T cells, post-infusion PBMC, and negative controls in duplex reactions with the HCK reference (REF) gene; assay C was chosen for further application.

Results: For all three dPCR assays clear separation of negative and positive signals was observed (Fig. 1A) resulting in perfect specificity. Reproducibility tested on individual patient samples was excellent with neglectable intra- and inter-assay variations. Based on dilution curves (Fig. 1B) and the established negativity of non-transduced cells, the limit of detection was determined to be one single CAR copy. Considering Poisson distribution this translates into a limit of quantification of three copies, i.e. any sample containing a mean of three target copies in the test volume could be expected to become positive with a likelihood >95%. In 100 ng genomic DNA (gDNA; approximately 30,000 haploid genome equivalents) this corresponds to a sensitivity of 0.01%. For male patients, a Y-chromosome located haploid reference gene was employed, which allows doubling the gDNA input and thus dPCR sensitivity. After thorough assay validation, we proceeded to monitor adoptively transferred Axi-cel T cells in 16 patients with advanced B-cell lymphoma treated at our centre (with informed consent) using assay C. Mean vector copy numbers were first assessed in the Axi-cel products, using leftovers from the infusion bags. CAR-T cells were reliably detectable in post-infusion samples of peripheral blood, bone marrow, and body fluids. Actual CAR-T numbers were calculated taking into account vector copy and PBMC numbers at the time point of analysis. We found robust CAR-T-cell expansion in 10 of our 16 patients with peak levels of up to 132 CAR-T cells/µL. The pattern of early CAR-T cell expansion and long-term persistence followed the kinetics previously described for Axi-cel patients.

Conclusions: We have established a novel dPCR assay for sensitive detection of Axi-cel CAR-T cells in vivo. Our assay is excellently suited as a diagnostic tool to monitor the infused cells in real-time in different body fluids.

[Figure 1]

Disclosure: The described dPCR assay is available as an ‘Expert Design Assay from Bio-Rad. BF, CB, AB, and KR would profit from commercialisation of the Assay.

King’s College Hospital NHS Foundation Trust, London, United Kingdom

Background: King’s College Hospital was an early UK commissioned centre delivering licensed axicabtagene ciloleucel (axi-cel) for the treatment of relapsed/refractory high-grade lymphoma starting in January 2019. Eligibility was determined through both NHS England’s National CAR Clinical panel and King’s College Hospital CAR multi-disciplinary team meeting for NHS and private patients respectively. Real-world European data is required to validate trial data and look for predictors of response and toxicity.

Methods: Eligible patients were aged >18 with diffuse large B-cell lymphoma (DLBCL), transformed follicular lymphoma (tFL) or primary mediastinal B-cell lymphoma (PMBCL), post 2 previous lines of treatment including anthracyclines. Adequate organ function was determined by King’s College Hospital and data on outcomes were collected prospectively.

Results: As of December 2019, 42 patients have been infused with axi-cel with a median follow-up of 6 months. The median age was 55 (range 18-73), 63% were male and 19% were aged 65 or over at infusion. All patients had ECOG performance status of 0-1 at time of referral. 27 (64%) had DLBCL, 12 (29%) transformed follicular lymphoma and 3 (7%) PMBCL. 11 patients had previous transplants (26%), 3 allogeneic and 8 autologous.

Median time from leukapheresis to infusion was 36 days. Most patients received bridging therapy between leukapheresis and infusion, 20 (47%) with chemotherapy, 8 (19%) with radiotherapy and 10 (23%) with steroids only.

Toxicity was graded as per consensus ASTCT guidelines (Lee et al. BBMT 2019) with 41 patients evaluable. Grade 3 cytokine release syndrome (CRS) occurred in 5 patients (12%) with no grade 4 or 5 events. 40 patients (98%) had CRS of any grade, with 32 patients (78%) being treated with tocilizumab for CRS grade 2 or above. 7 patients (17%) had grades 3 or 4 immune effector cell associated neurotoxicity syndrome (ICANS) with 14 patients (34%) experiencing any grade. 41% of patients received steroids for CRS or ICANS management. There was one grade 5 event from pneumonia and sepsis. 16 patients were treated on intensive care (39%), however 8 of these patients only required observation.

38 patients had an evaluable response at 1 month, with 82% overall response rate (ORR) and 37% complete metabolic remission (CMR), at 3 months of 34 evaluable patients 44% ORR and 23% CMR. Overall survival of the infused cohort was 67% and 14 (33%) patients have moved to further therapies. Median progression free survival (PFS) was 3.6 months and was significantly inferior in patients with 3+ prior therapies, with extranodal disease and with DLBCL compared to tFL.

Conclusions: CD19 CAR T cells have been safely delivered in the NHS and our large single centre cohort demonstrates lower toxicity with axi-cel, particularly of ICANS then described in a recent large CIBMTR cohort (Pasquini et al. ASH 2019). Initial response rates are high although PFS is lower than expected. Interestingly, 3+ prior therapies were associated with inferior PFS, implying patients may benefit from earlier referral for consideration of CAR T cells. By EBMT further follow-up will allow 6-month outcomes and predictors of response to be presented.

Disclosure: Sanderson, Robin - Advisory boards/honoraria: Novartis, Kite/Gilead.

Benjamin, Reuben - Advisory boards/honoraria: Novartis, Kite, Celgene, Takeda, Jannsen, Amgen. Research funding: Servier, Allogene, Pfizer.

Kuhnl, Andrea - Honoraria: Kite. Research funding: Novartis.

¹Hospital Clinic, Barcelona, Spain, ²Hospital Sant Joan de Déu, Barcelona, Spain, ³Immunotherapy Platform Clínic-Sant Joan de Déu, Barcelona, Spain, ⁴Banc de Sang i Teixits, Barcelona, Spain, ⁵University of Barcelona, Barcelona, Spain

Background: Sinusoidal obstruction syndrome (SOS) is a life-threatening adverse event occurring mostly in the context of allogeneic hematopoietic stem cell transplant (alloHCT), with a mean incidence of approximately 14% (2-31%, depending on conditioning regimen and individual patient risk factors). Novel immunotherapy agents like inotuzumab-ozogamicin (IO) can also increase the risk of SOS in this setting. In the pivotal trial, the risk of SOS was 8.6% for patients who received standard of care therapy plus alloHCT and 24.6% for those who received IO plus alloHCT (Kantarjian HM, 2019). However, there is little data on the incidence of SOS after other novel agents like CAR-T cells.

Methods: The first academic pilot clinical trial (clinicaltrials.gov NCT03144583) using our fully academic (A3B1:CD8:4-1BB:CD3Z) CAR19 (ARI-0001 cells) finished recruitment in June/2019. Eligibility criteria included CD19+ R/R B-ALL (adult and pediatric), NHL and CLL who had failed standard available therapy. Lymphodepletion was with fludarabine (90 mg/m²) and cyclophosphamide (900 mg/m²), and the cell dose was 0.4-5 x10⁶ ARI-0001 cells/kg, first as a single infusion (first 15 patients, cohort 1), and then in 2-3 fractions (last 23 patients, cohort 2). Here we report a descriptive analysis on the incidence of SOS in B-ALL patients included in this trial.

Results: We treated 38 R/R B-ALL patients with ARI-0001 cells. Median age was 24.5 years (3-68). All but 5 patients had relapsed after alloHCT (33/38 = 86.8%), and among patients with history of IO treatment (15/38 = 39.4%) only one had not previously undergone an alloHCT. We observed a total of 3 (7.9%) cases of SOS (see table 1) after ARI-0001 treatment, all occurring at cohort 2. The first 2 cases where 2 adult patients of 54 and 68 years diagnosed using the modified Seattle criteria in the context of weight gain, ascites, severe thrombocytopenia, increase in transhepatic gradient, and finally, confirmed by transjugular liver biopsy at day +31 and +49 after ARI-0001 cell infusion. Both patients had previous history of alloHCT and IO treatment with an inconclusive history of liver toxicity after IO treatment. They improved clinically from their SOS with support treatment and were eventually discharged from hospital. The third SOS case occurred in a post alloHCT young female patient (19 years) that after receiving ARI-0001 cell therapy was treated in another hospital with IO (day +161) and shortly after was diagnosed and treated as a SOS at day +171. This patient improved clinically after defibrotide treatment and was eventually discharged from hospital.

Conclusions: The incidence of SOS in patients with R/R B-ALL treated with ARI-0001 cells was 7.9%. However, it was 20% among those patients with both alloHCT and IO treatment. No SOS occurred in patients without prior alloHCT plus IO treatment. These results led us to incorporate liver imaging studies to our screening tests in patients with prior alloHCT/IO history who are referred for ARI-0001 cell therapy.

Clinical Trial Registry: Phase I, CART19-BE-01 clinical trial (EudraCT: 2016-002972-29, NCT03144583) for relapsed/refractory CD19+ leukemia and lymphoma at the Hospital Clínic de Barcelona and Hospital Sant Joan de Déu, Barcelona (Spain).

Disclosure: Source of funding: Proyecto ARI; Fundació Gloria Soler; ISCIII; CatSalut; FEHH; Generalitat de Catalunya

¹Hospital Clínic, Barcelona, Spain, ²Hospital Sant Joan de Déu, Barcelona, Spain, ³Institut d’Investigacions Biomèdiques August Pi i Sunyer IDIBAPS, Barcelona, Spain, ⁴Banc de Sang i Teixits (BST), Barcelona, Spain, ⁵University of Barcelona, Barcelona, Spain

Background: Chimeric Antigen Receptor (CAR)-T cells directed against CD19 have induced high rates of response in patients with relapsed/refractory (R/R) B-cell malignancies. Two CD19-targeting constructs have been approved by the FDA and EMA for B lymphoblastic leukemia (B-ALL) and aggressive lymphoma. Despite deep remissions, there are still major challenges and disparate data are reported about the immunogenicity induced by CART-cell therapy. The Spanish Agency of Medicine approved our first clinical trial with a fully academic CART-19 on May/2017.

Methods: Patients with R/R B-ALL (adult and pediatric), non-Hodgkin’s lymphoma (NHL) and chronic lymphocytic leukemia(CLL) who failed standard therapy were included in the trial. The primary objective of the study was safety; secondary objectives were response rate and its duration. After lymphodepletion with fludarabine (90 mg/m2) and cyclophosphamide (900 mg/m2), a total dose of 0.5-5 x10⁶ ARI-0001 cells/kg was infused (CAR-T with a single-chain variable fragment (scFv) with anti-CD19 specificity, conjugated with the co-stimulatory regions 4-1BB and CD3z; the scFv was originated from a mouse monoclonal antibody A3B1). The humoral anti-CART response was assessed by a cell-based fluorescence assay to detect human anti-murine antibodies (HAMA) in patients´ sera. Assessment was conducted at different time points: 1) at baseline (pre-dose), 2) on day 14 after the administration of ARI-0001 cells, 3) on day 28, 4) on day 100, and 5) every 3 months thereafter.

Results: Forty-seven patients (37 adults/10 pediatrics) received ARI-0001 cells. Thirty-eight patients had a diagnosis of R/R B-ALL (28 adults and 10 children); all but 5 had relapsed after allogeneic hematopoietic stem cell transplant (HCT). Seven patients had a diagnosis of NHL, four of them (57%) had relapsed after HCT, and 2 patients had a diagnosis of CLL. Median age was 27 years (3-68). Twenty-five per cent of the patients tested positive for the presence of anti-CAR antibodies, all of them post-dose, in contrast to previous data reported on Kymriah ® with a significant presence of pre-dose anti-murine CAR19 antibody. Of these patients, 8 patients presented with a weak, and 4 patients with a strong presence of HAMA. The last had lost the effectiveness of the CART-therapy at that time point since a simultaneous B-cell recovery was observed in the periphery. Moreover, three of them received a second dose of CART-19, which did not revert the relapse.

Conclusions: These data suggest the importance of the immunogenicity induced by CART-cell therapies. Immune monitoring should include the assessment of humoral response, especially before considering a second dose after relapse.

Clinical Trial Registry: Identifier: NCT03144583

https://clinicaltrials.gov/ct2/show/NCT03144583

Disclosure: Nothing to declare.

Kings College Hospital NHS Foundation Trust, London, United Kingdom

Background: Chimeric antigen receptor T (CAR-T) cells have shown promising results in treating patients with relapsed/refractory (R/R) B cell malignancies. With the recent approval of both axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisagen) for the treatment of R/R high-grade B non-Hodgkin lymphoma (NHL), we see more patients being referred for this novel therapy. There have been some published data looking at short- and long-term infection risks with this therapy and hypogammaglobulinaemia associated with B cell aplasia.^1,2

We look at our cohort of patients being treated at Kings College Hospital with Axi-cel or Tisagen for R/R NHL to identify our incidence of short- and long-term infections and to identify risk factors that may contribute.

Methods: We collected our single centre’s data on patients treated with CD19 CAR-T cells from Jan-Aug 2019. Eligibility is determined independently by a panel of clinical experts from NHS England and clinical data collected prospectively.

Results: A total of 31 patients were treated with axi-cel and 3 patients with tisagen during this period. All developed neutropenic fevers with at least Grade 1 cytokine release syndrome (CRS). A total of 26 patients required tocilizumab for CRS and 12 patients needed steroids for Grade 2 CRS unresponsive to tocilizumab. 3 patients had positive blood cultures within the first 28 days of CAR-T infusion and only 1 patient required treatment for proven fungal chest at D28. In regards to late infections, one patient had pneumocystis pneumonia at 6 months and another had line associated acinetobacter sepsis at 2 months in the setting of persistent neutropenia. 8 patients had positive respiratory viruses with 5 achieving lymphocyte recovery post CAR-T. 25 patients had B cell aplasia pre-CAR-T therapy and by 1 month nearly all patients had B cell aplasia. Pre-CAR-T 10 patients had IgG levels < 4g/L with 2 having regular immunoglobulin replacement prior and at 1-month post treatment 14 patients had levels < 4g/L. 2 patients required regular immunoglobulin replacement post CAR-T; one was for bronchiectasis. The other patient had significant infections within the first 100 days, this included HHV6 encephalitis, recurrent E. coli UTIs, Kliebsiella bacteraemia and pneumonia; he was treated with antibiotics as well as immunoglobulin replacement. One patient in remission died suddenly in their local hospital of sepsis at 7 months. All patients had routine prophylaxis with aciclovir, co-trimoxazole and fluconazole; patients were changed over to posaconazole as per hospital policy if evidence of prolonged neutropenia.

Conclusions: In our cohort most patients treated with CAR-T cells did not appear to have an increased risk of early or late infections and this is despite CRS and administration of tocilizumab and steroids. There was 1 patient who had significant infections post CAR-T likely due to persistent neutropenia and lymphopenia and another who died of late sepsis. Despite significant B cell aplasia pre and post CAR-T the immunoglobulin levels in most patients remained >4g/L which suggests that the humoral immune system can remain intact despite B cell aplasia. Immunoglobulin levels will be correlated with 6-month outcomes in final analysis.

Disclosure: Nothing to declare.

Sheba Medical Center, Tel Hashomer, Israel

Background: Chimeric antigen receptor (CAR) T cells have shown promising results in patients (pts) with B cell malignancies, yet up to 60% of the pts with diffuse large B cell lymphoma (DLBCL) will eventually relapse. Therefore, future efforts are needed to improve the outcomes of these pts.

Methods: A total of 22 pts with relapsed/refractory B cell malignancies, DLBCL (n=21) and ALL (n=1), were enrolled on a phase 1b/2 study (NCT02772198) of locally produced CD19 CAR T cells. All pts received a lymphodepleting preparative regimen with cyclophosphamide and fludarabine, followed by intravenous infusion of autologous CD19 CAR-T cells with a CD28 costimulatory domain. Clinical response was determined at 28 days following cell administration. Blood samples obtained prior to the lymphodepleting conditioning and at days 7, 14, 21, 30 and 60 after CAR T administration were collected. The manufactured CAR T products (n=11) were also subjected to immunophenotypic analysis.

Results: Clinically, 14 of 22 pts (63.7%) responded to CAR T therapy, 6 (27.3%) with complete response (CR), and 8 (36.4%) with partial response (PR). Analysis of the manufactured CAR T products revealed high CXCR3 expression (76% and 95% positive within the CD4+ and CD8+ subsets), indicating high migratory capacity of CAR T cells toward inflamed tissues. Furthermore, co-expression of CXCR4 (54% and 52% positive within the CD4+ and CD8+ cells) suggests increased homing ability of the manufactured CAR T toward CXCL12-rich bone marrow and lymph nodes. Interestingly, higher CCR7 expression (27.5% vs 8.5%) and lower CCR6 levels (14% vs 28%) were detected on CD8+ CAR T cells from responding pts who achieved CR and PR (n=8) versus non-responders (n=3), suggesting that less differentiated phenotype together with increased trafficking of CAR T to lymphoid tissue corresponds with improved clinical outcome.

Additionally, we assessed the immunoregulatory and senescent/exhausted phenotype in the CAR T products. Low percentage of CD4+CD25+CD127- Treg cells (13.5%, range 7-18%) was detected, with no correlation to clinical response. However, significantly higher frequency of exhausted CD57+CD39+CD28- cytotoxic CD8+ cells stand out as signature population in CAR T products of non-responders in comparison to CR pts (37% vs 9.5%, p< 0.02).

It is known that immunosuppressive environment affects CAR T cell activation. Notably, responding and non-responding pts presented distinct Treg patterns. Pts achieving CR demonstrated modest and delayed increase in Treg cells, reaching maximal frequency of 23% Treg out of CD4+ cells (range 17-30%) at day 21 post-CAR-T infusion, declining to basal low levels (12.5%) at day 30. In contrast, non-responders possessed rapidly increasing % of Treg cells (35%, range 25-50%, at day 14 post-infusion). In line with this finding, notable increase in proportion of immunosuppressive CD11b+CD14+CD163+CD206+ myeloid cells was detected in blood of non-responders, while pts achieving CR experienced transient increase in myeloid suppressor cells at day 7 that went back to normal levels at day 14.

Conclusions: Overall, these results elucidate in part the mechanisms of CAR T traffic, immunosuppressive responses as well as induction of T cell senescence/exhaustion that most probably downregulate CAR T effectiveness as observed in non-responding pts.

Clinical Trial Registry: NCT02772198

Disclosure: Nothing to disclose

King’s College Hospital NHS Foundation Trust, London, United Kingdom

Background: The anti-CD19 CAR-T therapies Axicabtagene ciloleucel and Tisagenlecleucel are now in use in the UK for patients with high grade lymphoma refractory to chemotherapy. As part of their treatment schedule patients receive lymphodepletion with Fludarabine and Cyclophosphamide prior to CAR-T infusion. However, as well as early haematological toxicity attributable to these agents, a second wave of cytopenias is observed in some patients after initial count recovery.

Methods: 39 patients were admitted to King’s College Hospital between January and September 2019 and received anti-CD19 CAR-T therapy. Haemoglobin, neutrophil and platelet counts were interrogated from commencement of lymphodepletion until latest follow-up or myelosuppressive therapy for disease progression. Haematological toxicity was graded as per EORTC. Further clinical information was collected from electronic patient records.

Results: Of the 39 patients diagnoses totalled 28 DLBCL, 14 transformed FL and 1 PMBCL. 38 patients received Axi-cel, the remaining 5 received tisagen. Patients had follow up duration of between 2 and 11 months post infusion, median follow-up 169 days. Maximal early haematological toxicity, as well as at the time of response monitoring at day+28, day+100 and 6 months post treatment is summarised in the table below.

Almost all patients (38 of 39) experienced grade 3/4 neutropenia during the first 28 days post infusion. No patients were given GCSF prior to D+14 due to concerns regarding exacerbation of CRS but 18 received it subsequently. Despite this, grade 3/4 neutropenia persisted in almost half of patients at D+28 (43%, 16/37). Grade 3/4 haematological toxicity persisting at D+28 occurred in 43% of patients (9/21) with < /=3 prior lines of treatment compared to 56% (9/16) of patients with >/=4 previous regimens. Incidence was also equivalent in patients with or without prior HSCT: 44% (12/27) without, 50% (5/10) with. 13 patients received bridging chemotherapy between apheresis and lymphodepletion, whereas 26 received no bridging, steroids or radiotherapy. Recent chemotherapy correlated with cytopenia at D+28: no bridging chemotherapy 36% (9/25), bridging chemotherapy 75% (9/12) (P=0.029).

Rates of grade 2 or worse CRS were similar in those with or without cytopenias at D+28: 61% (11/18) vs 47% (9/19) patients. ORR was 80% on D+28 PET imaging in patients without grade 3 or 4 cytopenias (16/20) and 94% in those with cytopenias (16/17) (p=0.22). Haematological toxicity at D+28 was also compared to D+100 outcomes. 47% (8/17) of patients without D+28 cytopenias had a maintained response, compared to 44% of those with progressive disease (7/16).

Conclusions: Many patients experience late cytopenias following CAR-T, therefore close monitoring of blood counts is required following discharge. Persistent cytopenias on discharge appear to correlate with prior bridging chemotherapy and are not associated with responses at 3 month follow up. Further work, including correlation with cytokine levels, is needed to determine the cause of late cytopenias. With maturation and expansion of the patient cohort we hope to determine whether cytopenias may be related to expansion and persistence of CAR-T and correlate with positive outcomes.

Clinical Trial Registry: n/a

Disclosure: Nothing to declare.

¹Novartis Pharmaceuticals, East Hanover, NJ, United States, ²Kyoto University, Kyoto, Japan, ³Hokkaido University Hospital, Sapporo Hokkaido, Japan, ⁴National Cancer Center Hospital, Tokyo, Japan, ⁵Kyushu University Hospital, Fukuoka Prefecture, Japan, ⁶Kyoto University, Kyoto, Japan, ⁷Kyoto University, Kyoto, Japan, ⁸Novartis Pharmaceuticals Corporation, East Hanover, NJ, United States, ⁹Novartis Pharma AG, Basel, Switzerland, ¹⁰Children’s Hospital of Philadelphia, Philadelphia, PA, United States, ¹¹University of Pennsylvania, Philadelphia, PA, United States, ¹²Oregon Health and Science University, Portland, OR, United States

Background: We assessed the impact of ethnicity on efficacy, safety, and cellular kinetics in Asian and non-Asian relapsed/refractory (r/r) DLBCL or B-cell ALL patients infused with tisagenlecleucel (anti-CD19 CAR-T cell therapy).

Methods: Data were obtained from r/r DLBCL (JULIET, NCT02445248) and B-cell ALL (ELIANA, NCT02435849; ENSIGN, NCT02228096) patients.

Results: Safety, efficacy, cellular kinetics, transduced dose range, and immunogenicity in the Asian and non-Asian subgroups are summarized in the Table. The assessed product attributes (eg, total cell count, % T cells, viability, and transduction efficiency) were comparable between Asian and non-Asian patients.

Conclusions: Asian and non-Asian patient populations in both indications were comparable with respect to safety, efficacy, dose-response, product attributes, and cellular kinetics of tisagenlecleucel.

[Table: Safety, efficacy, cellular kinetics, transduced dose range, and immunogenicity in the Asian and non-Asian subgroups]

Clinical Trial Registry: NCT02445248, NCT02435849, NCT02228096

Disclosure: Ahmed Abdelhady: Employment: Novartis.

Hidefumi Hiramatsu: No relationship to disclose.

Takanori Teshima: Grants from Kyowa-Hakko Kirin, Novartis, Chugai, Sanofi, Astellas, Teijin Pharma, Fuji Pharma, Nippon Shinyaku; personal fee (honoraria and advisory board) from Merck Sharp & Dohme, Kyowa-Hakko Kirin, Takeda, Novartis, Pfizer, Bristol-Myers Squibb.

Koji Izutsu: Grants and personal fees from Novartis during the conduct of the study; grants and personal fees from Eisai, MSD, Takeda, Janssen, Mundipharma, Chugai, AbbVie, Bayer, Ono, Celgene; personal fees from Kyowa Hakko Kirin, Bristol Myers Squibb, Dainihon Sumitomo, Nihon Mediphysics, AstraZeneca; grants from Gilead, Zenyaku, Solasia, Symbio, Astellas, Amgen, Bayer, Daiichi Sankyo, outside the submitted work.

Koji Kato: Consulting or advisory role with AbbVie, AstraZeneca, Celgene, Chugai, Eisai, Janssen, and Novartis. Honoraria from Chugai, Takeda, MSD, Kyowa-Kirin, Janssen, Celgene, Ono, Dainippon-Sumitomo, AbbVie, Novartis. Research funding from Chugai, Takeda, Kyowa-Kirin, Abbvie, Eisai, Janssen, Novartis, Mundi, AstraZeneca, Celgene, Ono, MSD, Otsuka.

Satoshi Saida: No relationship to disclose.

Tatsuya Kamitori: No relationship to disclose.

Keiji Tasaka: No relationship to disclose.

Itaru Kato: No relationship to disclose.

Katsutsugu Umeda: No relationship to disclose.

Souichi Adachi: No relationship to disclose.

Karen Thudium: Employment: Novartis.

Edward Waldron: Employment: Novartis.

Alessandra Forcina: Employment: Novartis.

Andrea Chassot Agostinho: Employment: Novartis.

Stephan Grupp: Grants and personal fees from Novartis Pharmaceuticals, during the conduct of the study; personal fees from Jazz Pharmaceuticals, personal fees from Adaptimmune, personal fees from TCR2 Therapeutics, personal fees from Eureka Therapeutics, personal fees from Cellectis/Servier, outside the submitted work; In addition, Dr. Grupp has a patent Toxicity management for anti-tumor activity of CARs (WO 2014011984 A1) issued.

Richard T. Maziarz: Honoraria, Membership on an entity’s Board of Directors or advisory committees and Research Funding: Novartis; Consultancy and Honoraria: Incyte, Juno; Honoraria: Kite; Jazz Pharmaceuticals.

Tel Aviv University, Tel Aviv, Israel

Background: CD19-directed CAR T-cell therapy becomes a standard of care treatment for relapse/refractory DLBCL. Production of CAR-T cells requires transduction and expansion of the collected lymphocytes. However, little is known about the impact of disease duration and specific treatment regimens on the harvested lymphocytes. Additionally, no sufficient data on the impact of the lymphopheresis product on treatment outcome.

Methods: Tisagenlecleucel (Kymriah^TM, Novartis) was commercially approved in Israel on May-2019. Since June-2019, we performed in all sequential patients flow-cytometry-based-T cell subsets (naïve-cell, central-memory (Tcm), effector-memory (Tem) and terminally-differentiated-CD45RA+ cells (Temra)) in the apheresis and in the CAR-T. In addition, activation marker HLA-DR and exhaustion marker PD-1 were also evaluated in the paired samples. All patients had a follow-up PET-CT scan one-month post infusion for response evaluation. We analyzed the effect of disease duration and the pre-apheresis treatment regimens being administered on the apheresis T-cell immunophenotyping, as well as the correlation between immunophenotyping and treatment outcome.

Results: Between May and December 2019, 35 DLBCL patients were screened and considered for Tisagenlecleucel treatment. 29 (83%) patients underwent lymphopheresis and 21 patients received the product. The study cohort included 20 sequential patients for whom complete flow-based T cell immunophenotyping data were available. 30-day PET-CT was available in 12. Median age was 71 (range, 20-84) years and median duration of disease was 12 (range, 4-68) months. 38% received >3 lines of chemotherapy and 33% failed autologousHCT.

Of the different variables evaluated we observed statistically significant effect of bendamustine treatment(n=9) on apheresis T cell immunophenotyping resulting in lower percent of naïve CD4 T cells (CD45RA+CCR7+; 4.15±4.2% vs 10.4±7.5%, p=.05), higher percent of Tem CD4s (CD45RA-CCR7-; 71.3±15.9% vs 52.7±12.6%, p=.01), higher percent of PD1+ CD4 T cells (66.8±14.6% vs 41.5±17.9%, p=.27) and higher percent of activated HLA-DR+ CD4s and CD8s (68.2±17.5% vs 41.9±13.7%, p=.01 for CD4s, 63.7±20.8% vs 39.2±19.1%, p=.13 for CD8s). Prior autologous HCT was associated with a trend toward lower CD4 to CD8 ratio (0.459±0.146 vs 1.00±0.748, p=.076). Although immunophenotyping was not affected by the number of pre-pheresis treatment-lines, disease duration was correlated with lower percent of naïve CD4 (Spearman´s correlation coefficient=-.5, p=.02) and naïve CD8 T-cells (Spearman´s correlation coefficient=-.46, p=.04) (Figure 1).

[Figure 1: Scatter plot of correlation between duration of disease and naïve CD4 and CD8 count]

Among all analyzed T cell characteristics, only higher percent of pre-pheresis HLA-DR+ CD4s and CD8s were associated with higher incidence of CR (beta .78, p=.05 and .47, p=.09, respectively).

Conclusions: While there remains insufficient data to solidly confirm our hypothesis, it is reasonable to assume that pre-lymphopheresis disease duration and treatment history may affect pheresis product, which in-turn, determines the final CAR T-cell product and response to treatment. Preliminary data from our small cohort suggests that pre-pheresis bendamustine treatment is associated with more mature, activated and exhausted CD4 T-cell phenotype. Improved phenotyping to include additional exhaustion markers, as well as follow-up post CAR T-cell infusion (by evaluating peripheral blood CD19-Ig binding T cells) is ongoing.

Disclosure: Nothing to declare.

First Afilliated Hospital of Suzhou University, Suzhou, China

Background: Chimeric antigen receptor (CAR) T cells are emerging as a novel treatment modality that highly effective in the treatment of relapse/refractory B-cell lymphoma, providing alternative therapeutic options for patients who failed to respond to conventional treatment or relapse. Although highly remission rates have been reported with CAR-T cell therapy in relapse/refractory B-cell lymphoma, relapse or disease progression is common after CAR-T therapy. This current study is to better our understanding of whether consolidative hematopoietic stem cell transplantation(HSCT) confers superior survival outcomes to patients who got remission by CAR-T cells therapy.

Methods: Compare the efficacy and survival of CAR-T therapy followed by HSCT and CAR-T alone in patients with relapsed/refractory B-cell lymphoma. 30 cases with CR or PR disesse status after CAR-T cells therapy in the First Affiliated Hospital of Soochow University from 2017 to 2019 were included. 11 of these cases (36.7%) were treated with HSCT after CAR-T therapy, of which 7 cases were treated with autologous stem cell lymphoma(ASCT), and 4 cases were treated with allogeneic stem cell transplantation(Allo-SCT). 19 of these cases (63.3%) were treated with CAR-T only. Overall survival(OS) and progression-free survival(PFS) rates were estimated by the Kaplan-Meier method, and Survival comparison was analyzed by using the log-rank test.

Results: Kaplan-Meier survival curve indicated that PFS of the HSCT following CAR-T group were higher than the CAR-T group, and log rank test showed that the difference of survival curve was statistically significant (P = 0.044). The estimated 1-year and 2-year progression-free survival(PFS)were 90.9%and 50% respectively in the CAR-T followed by HSCT group. The estimated 1-year and 2-year progression-free survival(PFS)were 71.6% and 27.8% respectively in the CAR-T group. Kaplan-Meier survival curve analysis indicated that OS of the HSCT following CAR-T group were higher than the CAR-T group, while log rank test showed that the difference of survival curve was no statistically significant (P = 0.250). The estimated1-year and 2-year overall survival(OS) were 90% and 89.4% respectively in the HSCT following CAR-T group, the estimated1-year and 2-year overall survival(OS) were90%and66.2% respectively in the CAR-T group.

Conclusions: Hematopoietic stem cell transplantation(HSCT) appear to improve progression-free survival (PFS) for the patients achieving remission following CAR-T therapy with relapse/refractory B-cell lymphoma. Future prospective studies needed to clearly define the role of consolidative HSCT in the relapse/refractory B-cell lymphoma patients who attained remission from CAR-T infusion and importantly, better identify this strategy whether exhibits superior overall survival outcomes.

Disclosure: there is no conflict of interest or source of funding

¹University Hospital Heidelberg, Heidelberg, Germany, ²Insitute of Clinical Transfusion Medicine and Cell Therapy (IKTZ), Heidelberg, Germany

Background: In patients with relapsed or refractory B-lineage acute lymphoblastic leukemia (ALL) or B-cell non-Hodgkin’s lymphoma (NHL) therapy with chimeric antigen receptor T (CAR-T) cells has proven to be highly effective. As starting material for the production of CAR-T cells T lymphocytes from the patients are mandatory. To harvest sufficient lymphocytes, leukapheresis as first step in the production process has to be performed. This constitutes a challenge to the treating physicians with regard to timing of the apheresis in heavily pretreated patients suffering from rapid progressive disease and being treated by drugs with negative impact on T cells.

Methods: Data from 45 adult patients suffering from r/r DLBCL (68%), PMBCL (2%), MCL (4%), FL (2%), CLL (4%), ALL (13%) or multiple myeloma (5%) who received a leukapheresis for CAR-T cell production were analyzed. Apheresis procedures were effective using the Spectra Optia™ device. Peripheral blood counts pre- and post-apheresis, as well as leukapheresis product parameters were assessed. Further important tasks were the analysis of the medication used prior to apheresis and the optimization of the apheresis procedure. Fourteen leukapheresis products were produced for clinical trials including 11 patients in our in-house production HD-CAR-1 study.

Results: All patients qualified for leukapheresis due to the following criteria: hemoglobin > 8g/dl, platelets > 75/nl, ANC > 1/nl, ALC > 0.3/nl, negative PCR for HBV, HCV, HEV and HIV; no active GvHD, no florid infection, no severe impairment of cardiac or pulmonary function. Leukapheresis was feasible in all patients and could be performed through peripheral venous access using the Spectra Optia™ device without any serious side effects. In total we performed 48 leukaphereses. 45 patients received a single apheresis and in three patients a later second apheresis was required due to infectious complications or electrolyte disturbance leading to a manufacturing failure. CAR T cell production was feasible for 44 of 45 patients. A mean blood volume of 11.8 (range 5.8-15) L was processed over a time of 238 (120-326) minutes. The leukapheresis product contained a mean of 11.8 x 10^9 (0.9-34.1 x 10^9) total nucleated cells and 4.9 x 10^9 (0.4 - 23.2 x 10^9) CD3+ T cells with a viability of 99.9 (99.6 - 100) % in a mean volume of 235 (136 - 310) ml with a hematocrit of 3 (1.1 - 7.4) %.

Conclusions: Leukapheresis was feasible in all patients in an out-patient setting. To harvest a sufficient number of lymphocytes for CART cell production, a minimum of 12 -15 L total blood volume should be processed in patients with an ANC 1-3/nl and ALC 0.3-1/nl. We established therefore a standardized procedure for the apheresis handling and developed a recommendation list for the timing of the medication before apheresis.

Disclosure: MS: Apogenix: Funding for collaborative research. Hexal: Financial support for research on biosimilars, travel grants. Kite: Financial support of educational activities and conference, travel grants. Co-PI of clinical trials on CAR-T cells. MSD: Ad board member, PI of clinical trials on letermovir. Novartis: Collaborative research grant. Co-PI of clinical trials on CAR-T cells. TolerogenixX: Co-Founder and shareholder.

AS: TolerogenixX: Co-Founder and shareholder, Mallinckrodt-Therakos: research grant, Jazz: travel grant.

PD: Advisory boards Novartis, Kite/Gilead

¹CNIO, Madrid, Spain, ²Hospital Universitario La Paz, Madrid, Spain, ³INGEMM, Madrid, Spain, ⁴CNB, Madrid, Spain, ⁵Hospital 12 de Octubre, Madrid, Spain, ⁶Idipaz, Madrid, Spain

Background: NKG2D is an NK cell activating receptor that recognizes different stress-induced ligands (NKG2DL) that are overexpressed in different pediatric and adult tumors, while their expression in healthy tissues is rare. NKG2D-CAR T cells have shown potent antitumor effects against different types of cancer. However, tumor cells may develop immune escape strategies such as ligand release (sNKG2DL), whose effect on NKG2D-CAR has not been studied and could affect their clinical efficacy.

Methods: Clinical grade NKG2D-CAR memory (CD45RA^-) T cells were produced by lentiviral transduction (NKG2D-41BB-CD3z, MOI = 2) and expansion in CliniMACS Prodigy. NKG2D-CAR memory T cells were infused in two patients excluded from CD19 CART cell trial with refractory relapse after hematopoietic stem cell transplantation. Patient#1 suffered from r/r biphenotypic ALL. She received two cycles of CAR T cells infusions. In the first cycle, a total of 3x10⁷ cells/kg were infused into three weekly doses with no conditioning. In the second cycle, a total of 2x10⁷ cells/kg were administered weekly into two doses after lymphodepleting conditioning with Cy/Flu and low dose bortezomib. Patient#2 suffered from r/r B-ALL and bronchopulmonary aspergillosis. She received a single dose of 1x10⁷ cells/kg after lymphodepleting conditioning Cy/Flu and low dose bortezomib. sNKG2DL concentration was monitored in the patient´s sera by ELISA. The effects of sNKG2DL on NKG2D-CAR T cells (NKG2D expression, proliferation, cytokine release and cytotoxicity) were explored after exposition to different concentrations of sNKG2DL for 7 days, by flow cytometry, ELISA or LUMINEX, and a 2 hour-degranulation assay using K562 cells as target, respectively.

Results: NKG2D-CAR memory T cells were infused without severe side effects. Patient #1 showed no cytokine release syndrome (CRS), hypotension, pain or neurological events. At day +28 after the first infusion and one week after the first dose of the second cycle she developed pruriginous skin rash. Biopsy described toxicodermia versus grade I skin GvHD. Bone marrow evaluation described leukemia progression. Only 24 hours after infusion, patient #2 presented a respiratory impairment without fever and other CRS symptoms and required intensive care. Ten days after the CAR-T cell infusion, bone marrow aspiration revealed blast persistence and the family suggested to limit the therapeutic effort. Patient#2 showed an increase on sULBP2 compared to control. After NKG2D CAR T cells infusions, sNKG2DL trended to decrease in both patients. In vitro, physiological concentrations of sNKG2DL increased NKG2D-CAR expression. However, supra-physiological levels of sNKG2DL reduced NKG2D-CAR expression, increased cell proliferation, and stimulated TNF-a and IFN-g production, which was further increased in the presence of IL-2. High doses of sMICA decreased degranulation of NKG2D-CAR T cells, which was associated with receptor down-regulation. The effects of sNKG2DL were dose-dependent and slightly attenuated by IL-2.

Conclusions: NKG2D CAR memory T cells are essentially safe. Only supraphysiological levels of sNKG2DL caused NKG2D-CAR downmodulation, while normal levels induce cell proliferation and production of pro-inflammatory cytokines. Altogether these data suggest NKG2D CAR could be more resistant to the negative effects of sNKG2DL than endogenous NKG2D receptor. However, we did not observe a beneficial clinical effect in this advance situation.

Disclosure: The authors have nothing to disclose.

Hannover Medical School, Hannover, Germany

Background: Chimeric antigen receptor (CAR) T cell therapy is often accompanied by potentially life-threatening cytokine release syndrome (CRS). The role of T regulatory cells (Tregs) during CRS remains to be elucidated. Here we prospectively investigated the Tregs population in patients with and without CRS after anti-CD19-CAR T Infusion.

Methods: The cohort consisted of 11 patients with relapsed or refractory transformed follicular lymphoma and diffuse large B cell lymphoma (DLBCL). All received anti-CD19-CAR T infusion (Tisagenlecleucel) after lymphodepletion with fludarabine and cyclophosphamide. All patients gave written informed consent to participate in the study. Patients were grouped based on emergence of CRS. Tregs were detected from peripheral blood via flow cytometry by staining for CD4+CD25+CD127dim- lymphocytes. To determine the absolute frequencies BD Trucount™ tubes were employed. Three time points were selected for analysis: baseline (d-1 - d+2 from Tisagenlecleucel infusion); 1 day prior or at the day of CRS diagnosis before start of CRS treatment (TP1, d+1 - d+6); after CRS clearance (TP2, d+3 - d+10). As control group served patients without CRS using comparable time points.

[Figure 1: Tregs frequencies in CRS vs no CRS patients.]

Results: Four patients met CRS criteria (Grade 1-4). On 3/4 CRS patients blood samples were available at all three time points and these were thus selected for analysis. Upon emergence of CRS (TP1) Tregs (measured in frequency of lymphocytes) showed a mean reduction of -46.91% compared to the baseline time point while the no-CRS controls increased their frequency by on average +10.57% (Figure 1A). Inter-group comparison at TP1 revealed differences of Tregs levels (0.87 vs. 3.10 % of lymphocytes) as well as in absolute Tregs count (1.79 Tregs/µl vs. 8.84 Tregs/µl, Figure 1B). Tregs frequencies in patients after CRS clearance (TP2) increased on average by 3.05-fold compared to TP1 while Tregs frequencies stayed stable in controls (Figure 1A). Based on this increase, Tregs frequencies at TP2 were similar to values of no-CRS patients. These findings are limited by the small patient number and in general low frequencies of Tregs early after CAR T infusion. Therefore, these pilot data need validation in a larger cohort.

Conclusions: In this prospective single center pilot study, blood samples of emerging CRS showed a reduction of Tregs frequencies and absolute numbers compared to no-CRS patients. After clearance of CRS, Tregs frequencies increased to values of no-CRS patients. Therefore, investigation of Treg frequencies as a predictive marker for CRS should be further investigated. However, future studies are needed to validate these findings in a larger cohort.

Disclosure: Nothing to declare.

University Medical Center Hamburg, Hamburg, Germany

Background: Allogeneic CAR-T cell therapy bears the potential to combine graft-versus-malignancy effects and CAR-directed target killing, but comes with a considerable risk of graft-versus-host disease (GVHD). Animal studies indicate that the risk of GVHD after CAR-T infusion from an allogeneic donor may in part depend on the costimulatory domain used, first generation and 4-1BB-based CAR-T cells bearing an increased risk of GVHD [Gosh et al., 2017]. Interestingly, in the only report on donor-derived CAR-T cells with a 4-1BB costimulatory domain, both patients developed acute GVHD [Dai et al., 2015]. Use of immunosuppression to prevent GVHD after CAR-T cell infusion may prevent their expansion and efficacy. Here we present for the first time data on expansion and persistence of 4-1BB based CAR-T cells under immunosuppression with clinically relevant concentrations of cyclosporine A.

Methods: A 64-year old female with early relapse of follicular lymphoma grade 3A (day 65 after allogeneic hematopoietic stem cell transplantation, allo-HSCT) consented for compassionate-use treatment with CAR-T cells. CD19-CAR-T cells were manufactured from freshly collected allogeneic donor leukocytes using the CliniMACS Prodigy system and a lentiviral vector encoding the CD19-CAR containing a 4-1BB costimulatory domain.

The patient received lymphodepleting chemotherapy with cyclophosphamide and fludarabine and 1 x 10⁶ /kg BW CAR-expressing cells on day 0 (3 months after allo-HSCT). Because the patient had history of acute GVHD, we maintained her on GVHD prophylaxis with cyclosporine A at a mean cyclosporine A trough level of 170 µg/l (range 122-206 µg/l) until day 21 after CAR-T cell infusion. With no evidence of active GVHD, cyclosporine A was tapered off from day +21 and stopped on day +56 after CAR-T cell infusion.

[Figure 1: CAR-T cell expansion and persistence]

Results: No CRS or ICANS were observed. Haematopoietic recovery was expectedly slow despite use of G-CSF as from day +21. Stable neutrophil counts > 1000/µl without further G-CSF support was attained on day 32, platelet count > 50.000/µl on day 150 after CAR-T cell infusion.

FDG-PET scan on day +30 revealed complete resolution of most of the lymphoma manifestations seen in the CT scan, but also showed new bone lesions in both sacrum and femur. A follow-up FDG-PET scan on day 120 showed regression of all lymphoma manifestations with only residual manifestations in the left sacrum.

Highest CAR-T cell numbers were measured on day +9 (50 CAR-T cells/µl) with continuous persistence of CAR-T cells up to the last examination 6 months after infusion (figure 1). While overall T cell reconstitution was well evident, B cell aplasia is persistent. Interestingly, the analysis of the CAR-T cells for activation and exhaustion markers revealed a decline in the fraction of effector and effector memory and a relative increase in central memory CD4+ CAR-T cells.

Conclusions: In conclusion, we for the first time present data on proliferation and persistence of allogeneic donor-derived 4-1BB based CAR-T cells under therapeutic levels of cyclosporine A. This indicates that for patients with early relapse after allo-HSCT with ongoing immunosuppression donor CAR-T cell therapy may be a feasible Treatment.

Disclosure: Nothing to declare.

¹CRYOSTEM, Marseille, France, ²Hôpital Saint Louis, AP-HP, Paris, France, ³Hôpital Robert Debré, AP-HP, Paris, France, ⁴Institut Paoli-Calmettes, Marseille, France, ⁵CHU Rennes, Rennes, France, ⁶Institut Universitaire Cancerologie Toulouse-Oncopole, Toulouse, France, ⁷Hôpital Saint-Louis, AP-HP, Paris, France, ⁸Institut Gustave Roussy, Villejuif, France, ⁹CHRU Lille, Lille, France, ¹⁰Hôpital Universitaire de Nantes, Nantes, France, ¹¹Hôpital Universitaire Henri Mondor, AP-HP, Créteil, France, ¹²Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Pierre-Bénite, France, ¹³CHU Saint-Eloi, Montpellier, France, ¹⁴CHU Rennes - Pontchaillou, Rennes, France

Background: Even if Chimeric Antigen Receptor (CAR)-T cells therapies are a promising way to treat relapsed/refractory hematologic cancers, authorities face major issues regarding their economic impact, the evaluation of their efficiency and adverse effects. Since their launch the number of patients with CAR-T cells indication is increasing, as well as the number of hematological cancers likely to be treated. Nationwide collections of biological resources are warranted to develop scientific projects to monitor CAR-T cells treatments and improve our understanding of the underlying biological mechanisms.

In this context, a biobanking initiative resulted from the collaboration of two French consortia : CALYM, gathering together the LYSA (Lymphoma Study Association), LYSARC (Lymphoma Academic Research Organization) and 18 academic laboratories in the field of lymphoma, and CRYOSTEM, a collaborative biobanking network. After demonstrating respectively their ability to set up the first collection of viable cells from lymphoma patients (CeVi_collection) and the first European collection of biological resources dedicated to Hematopoietic Stem Cell Transplantation, CRYOSTEM and CALYM joined their expertise to constitute a biocollection from lymphoma patients receiving CAR-T cells.

Methods: The collaboration between CRYOSTEM and CALYM networks brings together hematological clinical units and biological resources centers (BRCs) to include patients, collect and process samples. Any patient suffering from lymphoma, justifying a CAR-T cells treatment is eligible for inclusion. Several types of samples are collected and derived pre- and post-CAR-T cells administration following a specific timeline. CALYM BRCs are in charge of the treatment and storage of lymph nodes and bone marrow samples in viable cells whereas CRYOSTEM BRCs enrich this collection by processing blood samples in viable cells and plasma, and also stools and urines. Annotated biological samples are centralized in CALYM database.

Results: In less than one year, CRYOSTEM and CALYM set up the organizational and regulatory framework of the first collection of samples and associated data dedicated to CAR-T cells treated patients:

• Constitution of governing bodies including representatives from both organizations;

• Identification of the 9 clinical units and BRCs involved in the protocol;

• Practices harmonization and standardization regarding samples and protocols;

• Establishment of sampling kinetics integrated to patients’ care. Paired with lymph nodes, 8 blood sampling points are planned from apheresis to 6 months post-injection and/or at relapse;

• Estimation of the collecting rate of each sampling point according treatment failure and mortality rate;

• Evaluation of the annual number of inclusions.

First inclusions are planned in January 2020.

Conclusions: With the creation of the first biobank focused on CAR-T cells treated patients, the CALYM-CRYOSTEM collaboration opens new research perspectives by providing access to raw material. This approach would impact CAR-T cells treatments by providing a large amount of post-infusion data, contributing to consolidating knowledge on this recent cell-based therapeutic approach.

This initiative, focused on lymphoma, sets up the bases of the constitution of new type of collection integrating complementary expertise and actors in CAR-T care and research. It will constitute a proof of concept for other initiatives in this field, independently of the initial hematological disease.

Clinical Trial Registry: Non applicable

Disclosure: Any conflict of interest

¹University Hospital Heidelberg, Heidelberg, Germany, ²German Red Cross Blood Service Baden-Wuerttemberg-Hessen, Heidelberg, Germany, ³Diakonie Hospital Stuttgart, Stuttgart, Germany, ⁴Saarland University Medical Center, Homburg, Germany

Background: CD19-directed chimeric antigen receptor T cells (CARTs) have been successfully used in patients with acute lymphoblastic leukaemia (ALL) after a preceding allogeneic stem cell transplantation (alloHCT). However, data on feasibility and outcome of CARTs in patients previously allotransplanted for B-cell lymphoma are lacking. Here, we report our institutional experience in this setting.

Methods: Course and outcome of allo-grafted patients treated with CD19 CARTs for B-cell lymphoma between October 2018 and November 2019 were studied in a single-center retrospective analysis. CARTs were administered either as third-generation CARTs within the Heidelberg CART 1 (HD-CAR-1) clinical trial (Eudra-CT No. 2016-0048; NCT03676504), or with commercially manufactured second-generation CARTs Axicabtagene Ciloleucel (Axi-cel, Gilead). Number of infused CARTs ranged from 1x10⁶-2x10⁷/m² (HD-CAR-1) or were within the label-specified range (Axi-cel).

Results: 10 CART dosings using recipient leukapheresis products have been administered to 8 patients: 4 patients (2 mantle cell lymphoma (MCL), 2 CLL) received 6 infusions with HD-CAR-1 CARTs. 4 patients (all with DLBCL) received 4 infusions with Axi-cel. Lymphodepleting chemotherapy with flu/cy (30/500 mg/m²/d for 3 days) was administered to all patients prior to CART infusion. All 8 patients were male with a median age of 57 (27-70) years. A median of 4 (3-11) treatment lines had been administered during 5.8 (1.5-12.5) years from diagnosis. Median time from alloHCT to CART treatment was 2.4 (1.0-8.2) years. AlloHCT had been performed from matched related (MRD) (3), matched unrelated (MUD) (4), or haplo (1) donors after myeloablative conditioning. Acute and chronic GvHD after alloHCT had been observed in 2 and 6 patients, respectively. No patient had active GvHD or was under immune suppression at the time of leukapheresis and all patients had active disease. CART treatment was well tolerated with higher grade CRS and ICANS each being observed after 1 of 10 evaluable dosings. Patients had complete resolution of CRS and ICANS following administration of tocilizumab and steroids, respectively. A single patient had cutaneous and hepatic reactions suspicious of chronic GVHD early after dosing, whereas all other dosings were not accompanied by GVHD. CARTs were detectable in the peripheral blood (PB) in all but one patient. The patient developing ICANS displayed the highest CART frequency in the PB. With a median follow-up of 108 (18-314) days, all patients are alive with an overall best response rate of 88%. 3 of 7 evaluable patients achieved ongoing CRs. B cell aplasia and cytopenia were observed in all patients following CART dosings. B cell aplasia is ongoing in 8 instances and long-term (>1 month) leukopenia and thrombocytopenia were observed following 8 and 7 dosings, respectively.

Conclusions: Therapy with CARTs manufactured from recipient-derived leukapheresis products after prior alloHCT was feasible, safe and efficient. Therefore, CARTs as salvage treatment for patients with B-cell lymphoma relapsing after alloHCT constitute a justifiable treatment option. Cytopenia as a result of multiple myelotoxic treatments needs to be carefully monitored.

Disclosure: Dreger: AbbVie, AstraZeneca, Gilead, Janssen, Novartis, Riemser, Roche: Consultancy; AbbVie, Gilead, Novartis, Riemser, Roche: Speakers Bureau; Neovii, Riemser: Research Funding; MSD: Membership on an entity´s Board of Directors or advisory committees, Other: Sponsoring of Symposia. Schmitt: Therakos Mallinckrodt: Other: Financial Support. Sellner: Takeda: Employment. Müller-Tidow: MSD: Membership on an entity´s Board of Directors or advisory committees. Schmitt:Therakos Mallinckrodt: Other: Financial Support; MSD: Membership on an entity´s Board of Directors or advisory committees, Other: Sponsoring of Symposia. Stilgenbauer: Pharmacyclics: Other: Travel support; Gilead, Celgene, Amgen, AbbVie, Novartis, AstraZeneca, Hoffmann La-Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau.

¹Bambino Gesù Children’s Hospital, Rome, Italy, ²Campus Bio-Medico Univerisity, Rome, Italy, ³Sapienza University of Rome, Rome, Italy

Background: Chimeric antigen receptor (CAR) T-cell therapy is a novel anti-tumor strategy in which autologous T-cells are engineered to express a CAR construct targeting an antigen expressed on membrane malignant cells. The CAR T-cell manufacturing process consists of different steps performed by different units, namely apheresis, cell therapy laboratory and the clinical unit. The collection of patient’s T-cells by the apheresis unit is the first step, followed by the characterization and manipulation of the cell product.

Herein, we report on 70 apheresis procedures performed on children and young adults with hematological and non-hematological diseases who underwent PBMC purification and cryopreservation for subsequent CAR T-cell production for academic trials at our institution.

Methods: Seventy collections were performed between January 2017 and November 2019; 51 patients were males, 19 females, median age being 9 years (range, 3-25) and median body weight (BW) 24 kg (range, 11-106). Indication for CAR T-cell production was refractory/relapsed Acute Lymphoblastic Leukemia (ALL, n=27), non-Hodgkin’s lymphoma (NHL, n=6) or Neuroblastoma (NBL, n=37). Leukapheresis was performed by Spectra Optia using continuous and discontinuous mononuclear cell protocol (CMNC vs MNC), with a collection target >4x10*9 mononuclear cells (MC). In 37/70 (53%) cases, patients had a central venous double lumen catheter (CVC), 17/70 (24%) were collected through peripheral venous accesses (VP) and 16/70 (23%) using both approaches (CVC+VP). Sodium heparin and Acid Citrate Dextrose Solution-A (ACD-A) were used in combination as anticoagulants. After apheresis, a density gradient PBMC purification using the Sepax 2 device was performed and the MCs were eventually cryopreserved.

Results: The median lymphocyte counts before apheresis were 1080/ul (200-4070). Out of 70 collections, 34/70 were performed using MNC (49%) and 36/70 using CMNC (51%). For all patients, the median total blood volume (TBV) processed was 2.1L (0.59-4.3), while for patients < 15kg (11/70, 16%) the processed TBV was 2.7L (1.6-4.3). Apheresis bags contained a median of 5.2x10*9 nucleated cells (1.5-15.4). Lymphocyte collection efficiency (lympho-CE) had a median value of 68% (range, 24-100). 27 products from ALL patients, 6 products from NHL patients and 37 products from NBL patients underwent a density gradient purification for PBMC enrichment. For ALL and NHL patients, median recovery for MNC was 76% (61-93) and median red blood (RBC) depletion was 81% (45-94). Total MNC and CD3 cells were 2.75x10*9 (0.84-8.26) and 1.33x10*9 (0.58-2.74) respectively. For NBL patients, median recovery for MNC was 73% (54-89) and RBC depletion was 79% (64-96). Total MNC and CD3 cells were 2.7x10*9 (1.0-6.0) and 1.0 (0.4-8.0).

Conclusions: Sufficient numbers of cells can be obtained from pediatric patients with BW < 15 kg, with a median value of processed TBV of 2.7L (1.6-4.3), provided that their lymphocyte counts are >900/ul. All patients reached the target cells in a single apheresis, including 2 patients with lympho-CE < 30%. In 56/70 (80%) of collections, lympho-CE was ≥50%.

Density gradient purification with the Sepax device is helpful to remove a fraction of RBC, allowing subsequent cryopreservation of pure products in which CD3+ cell concentration is higher with respect to other cellular components.

Disclosure: Nothing to declare.

¹Mayo Clinic, Jacksonville, FL, United States, ²Mayo Clinic, Rochester, MN, United States, ³Mayo Clinic, Phoenix, AZ, United States, ⁴Azienda Ospedaliera Universitaria, Citta della Salute e della Scienza di Torino, Torino, Italy

Background: Axi-cel is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy that is approved for treatment of relapsed/refractory (R/R) large B-cell lymphoma and is associated with high response rates and durable remissions. Recent data show that axi-cel is effective across various adverse prognostic features, namely cell of origin, disease bulkiness, and extranodal disease, among others. Hypoalbuminemia is a known adverse prognostic factor in lymphomas. Yet, it is unknown if axi-cel overcomes the adverse prognostic feature of hypoalbuminemia in R/R large B-cell or transformed follicular lymphoma.

Methods: We conducted a retrospective analysis of patients treated with axi-cel across three Mayo Clinic campuses (Rochester, Jacksonville, and Phoenix) from 06/01/2016 until 12/01/2019. The primary objective of this analysis was to assess the correlation of hypoalbuminemia defined as a serum albumin levels ≤ 3.5 g/dL on day 0, prior to infusion on outcomes after axi-cel therapy.

Results: A total of 69 (male=48, 70%) patients (pts), median age of 53 (24-74) years received axi-cel. The median number of prior lines of therapy was 3 (2-8) (Table 1). Two pts had no available serum albumin levels at time of axi-cel infusion. Thirteen (19%) of 67 pts had hypoalbuminemia (median= 3.3 g/dL (range 2.5-3.5)) and the median follow-up of survivors in this group was 6.7 (1.7-17.8) months. The best overall response rate (ORR) and complete remission (CR) rates in these pts were 62% and 46%, respectively. One (8%) patient had stable disease and 4 (31%) had disease progression. On the other hand, 54 (81%) pts had a normal serum albumin (defined as > 3.5 g/dL) level (median=4.1 (range 3.6-5.1) g/dL) and the median follow up for survivors in this group was 5.4 (1.0-30.9) months. The best objective response rate (ORR) and complete remission (CR) rates in these pts were 81% and 41%, respectively. There was no difference in 1-year OS between the group with hypoalbuminemia (64% (95%CI=30-99%)) and the group with normal serum albumin level (57% (95%CI=34-79%), p=0.88. All grades cytokine release syndrome (CRS) was diagnosed in all 13 pts with hypoalbuminemia (100%) and in 48 of 54 (89%) pts without hypoalbuminemia. There was no difference in the median duration of CRS between pts with or without hypoalbuminemia [5 (1-11) days vs 5 (1-19) days, p=0.84]. Neurotoxicity (all grades) was observed in 8 (62%) pts with hypoalbuminemia compared 27 (50%) with normal albumin levels. There was no statistically significant difference in median duration of neurotoxicity between pts with hypoalbuminemia and those with normal baseline albumin levels [9 (range 1-56) days vs. 3 (range 0-25) days, p= 0.07].

Conclusions: Hypoalbuminemia does not have a significant impact on the outcomes of axi-cel therapy, including OS or the incidence of CRS or neurotoxicity. Large multicenter clinical trials are needed to validate these findings.

Clinical Trial Registry: None

Disclosure: Lin, Yi: Research funding: Janssen, Merck, Kite/Gilead, Celgene, BlueBird Bio, Takeda

Consulting: Janssen, Legend BioTech, JUNO, Celgene, BlueBird Bio, Kite/Gilead, Novartis, Gamida Cells, AlloGene.

DSMB: Sorrento

Steering committee: Celgene, Janssen, Legend Biotech

Hospital Gregorio Marañón, Madrid, Spain

Background: Chimeric antigen receptor (CAR) T cells are a promising new immunotherapy. However, the challenges of collecting CD3+ lymphocytes in this population of patients have not been well-characterized. The aims of the study were to evaluate the feasibility of collection adequate numbers of CD3+ cells, analyze the rate of adverse events and to identify the variables that can predict inadequate collections.

Methods: We prospectively study the apheresis for lymphocyte collections (ALC) from patients in real live for CARs from May-19 to November-19. Collections were performed on the same Cobe Optia device, at hematocrit of 1 to 2% and collection flow rate of 0.8 mL/min. All patients had Hickman central venous catheters placed before the procedure, and received intravenous calcium gluconate as per SOP. The product goal was a target of 1 x 10⁹ CD3+ cells.

Results: 14 ALC were performed. Median age 59.5 years (28-69). 57%(n=8) were male. 57%(n=8) were sent for the production of axicabtagene ciloleucel, 43% for tisagenlecleucel. Diagnosis was 100% lymphoma, median of 16.4 months from the diagnosis to ALC (6-48.8). Ann arbor stage was 3 in 2 patients(14%), 4 in 11 patients(79%). 50%(n=7) received 3 or more prior lines of treatment. Potential treatment affecting the collection prior apheresis: 36%(n=5) purine nucleoside antimetabolites, 21% (n=3) received IMiDs, 50%(n=7) Autologous Stem cell transplant and 36% (n=5) radiotherapy. Last treatment before ALC was systemic chemotherapy in 7 patients (57%), radiotherapy 4 patients (29%), immunotherapy 2 patients (14%). Median of 45 days from the treatment to ALC (15-1000).

[Correlation between pre-apheresis CD3+ (cells/µL) neutrophils and CD3+ yield]

Pre-apheresis laboratory testing were : median leucocyte(x 10⁶/mL) of 4 (1-14.4), median hematocrit (%) 30.2 (25-41), median platelets (x10⁶/mL) 112 (25-345), median neutrophils (%) 63.5 (34.3-86), median lymphocyte (%) 20.2 (30.8-50), median NK (%) 3.2 (0.3-8.7), median (%) CD19+ 0(0-4.8), median CD3+ (cells/µL) 460 (147-2770), median CD3+(%) 12.2(4-38) of which median CD4+(%) 37.25(10-72) and CD8+(%) 55.9 (24.5-85)

Apheresis parameters were: median of 12 liters processed (5-15), collection efficiency median (%) 52.9 (40.9-75.5). One patient developed symptomatic hypotension during the procedure, other complications related to hypocalcemia including paresthesias were managed in the apheresis unit.

Apheresis collection yields from 13 products were: median volume of 199 mL (86-240), median hematocrit(%) 3.2 (1.8-17.7), median platelets(x10⁶/mL) 811(255-3784), median volume ACD-A(mL) 22(10-31), cell concentration (cellsx10⁶/mL) 58.9 (12.7-247.7), median total nucleated cells (x10⁹) 9.9 (2.8-52.5), median mononuclear cells(x10⁶/mL) 51.3(12.6-242.7). Median(%) CD3+ of CD45+ was 53(23-83.5) with a median total number of CD3+ (x10⁹) of 5.2 (1.1-17.3).

Univariate analysis showed that higher pre-apheresis CD3+ (cells/µL) was significantly correlated with CD3+ total collected cells in the apheresis product. Thus, there is an association with higher proportion of neutrophils in peripheral blood with lower pre-apheresis CD3+ counts (figure1).

Conclusions: In most patients undergoing CART cell therapy, leukapheresis is well-tolerated and adequate numbers of CD3+ lymphocytes are collected. A personalized approach to the collection process is the essential first step for CART cell immunotherapy. However, further studies of larger cohorts of patients including new variables are necessary to confirm this findings to ensure that all patients can have sufficient cells for manufacturing.

Disclosure: Nothing to declare.

¹Hospital General Universitario Gregorio Marañón, Madrid, Spain, ²Great Ormond Street Hospital for Children, London, United Kingdom

Background: Tisagenlecleucel (Kymriah^TM) is a CD19-targeted CAR-T cell therapy approved for r/r B-ALL in paediatric/young-adult patients. Cytopenias following CAR-T cells are relatively common across multiple studies¹ including those targeting CD19 and CD22 and are therefore not antigen-specific. The incidence and clinical impact of persistent or recurrent cytopenias has been under-recognized in clinical studies to date and the aetiology is as yet unclear. The objective of this study is to describe cytopenias and related complications in paediatric/young-adult patients with r/r B-ALL treated with Tisagenlecleucel.

[1] Jacoby et al. 10.1038/s41409-019-0487-3

Methods: We retrospectively analyzed 12 consecutive patients with r/r B-ALL treated with Tisagenlecleucel between January 2019 and November 2019 in a single centre. Patients received lymphodepletion with fludarabine (120 mg/m2) and cyclophosphamide (1000 mg/m2). Cytopenias were graded according to CTCAE V-5.0. Persistent cytopenias were defined as grade 2-4 cytopenias after day-28. Recurrent cytopenias were defined as new-onset grade 3-4 cytopenias after day-28 when and after achieving normal counts on day-28. Cytopenias were considered resolved when grade 1 or normal counts were achieved.

Results: Patient characteristics are summarised in Table 1. Nine patients were diagnosed with relapsed B-ALL after HSCT, 2 had relapsed B-ALL with a contraindication for HSCT and 1 had primary refractory disease. With a median follow-up of 4 months (range 1-10) after CAR-T cell infusion, MRD was negative in 11 patients (92%), B cell aplasia was persistent in 10 (83%) and 1 (8%) had a relapse and died.

Eight patients (67%) presented with grade 2-4 cytopenias before lymphodepletion.

Before day-28, all patients developed grade 2-4 anaemia (9=75% grade 3-4), 8 patients (67%) developed grade 2-4 thrombocytopenia (6=50% grade 3-4), and all patients developed grade 3-4 neutropenia.

Four patients (33%) had persistent grade 2-4 anaemia, 2 (17%) grade 3-4. Five (42%) had persistent thrombocytopenia, all grade 3-4. Seven (58%) had persistent neutropenia, all grade 3-4. Two patients (17%) with normal counts on day-28, developed recurrent grade 3-4 neutropenia after day-28.

Secondary causes of cytopenias were excluded. Among patients with persistent cytopenias, 4 (50%) had a hypocellular marrow on histology of the BM trephine.

Eight patients (67%) received at least one RBC transfusion before day-28, and 2 (17%) after day-28. Three patients (25%) received at least one platelet transfusion before day-28, and 4 (33%) after day-28. Seven patients (58%) received at least one Filgrastim dose after day-28. Eight documented infections were diagnosed, 3 of them after day-28, with 0% of infection-related mortality.

At last follow-up, anaemia was resolved in all patients, 2 (17%) had ongoing thrombocytopenia, (1 with platelet transfusion dependence), and 3 (25%) ongoing neutropenia (1 with Filgrastim dependence).

Conclusions: Cytopenias were frequent in patients treated with Tisagenlecleucel. Whilst early cytopenias are expected due to lymphodepletion, mechanisms of persistent and recurrent cytopenias are unclear and might be related to CAR-T cells persistence. More studies are needed to determine etiology and risk factors for persistent cytopenias. Cytopenias are of relevance in terms of increased requirement for supportive care, however, in our cohort, were not associated with significant or persisting complications.

Disclosure: Nothing to declare.

¹The First Affiliated Hospital, Zhejiang University, Hangzhou, China, ²Zhejiang University, Hangzhou, China, ³Shanghai YaKe Biotechnology Ltd, Shanghai, Shanghai, China

Background: Chimeric antigen receptor- modified (CAR) T-cell immunotherapy is a novel promising therapy for relapsed/refractory B cell malignancies. Prolonged B- cell aplasia is a common and expected toxicity after receiving CAR-T cell treatment. However, the risk of HBV reactivation after CAR-T cell therapy is still unknown. We summarized the risk of HBV reactivation in R/R B-cell Malignancies patients with Concomitant Hepatitis B Virus infection after Chimeric Antigen Receptor T Cell Therapy at our hospital.

Methods: Patients with R/R B-cell lymphoma, B-ALL and Multiple Myeloma who received CAR-T cell treatment in four clinical trials (ChiCTR-ORN-16008948, ChiCTR-OIC-17011310, ChiCTR1800015575, ChiCTR1800017404) in our center were retrospectively analyzed. All patients were screened for hepatitis B surface antigen (HBsAg), antibody to hepatitis B surface antigen (anti-HBs), antigen antibody to hepatitis B core antigen (anti-HBc) and HBV DNA copy numbers before and after CAR-T cell treatment. Those with positive HBsAg were eligible for this retrospective study.

Results: Between December 2017 and October 2019, 10 patients with relapsed or refractory B cell malignancies and concomitant HBV infection who were treated with CAR-T cells were included in this study. The median age was 50 years (range: 39-67 years), with 60% were male. Details are summarized in table I. All of the 10 patients with chronic HBV infection received prophylactic entecavir treatment. And at the time of CAR-T cell infusion, HBV DNA levels of all patients were lower than the normal limit. With median follow-up 7.77 months (range:1.43-23.8 months) from CAR-T cell infusion, 2patients (patient 9 and patient 10) had transient HBV reactivation. However, the HBV DNA copy numbers came back to lower than the normal limit with the entecavir and Adefovir treatment. All patients reminded on prophylactic NAT by the time of last follow-up. Figure1 showed the Time points of HBV detection and response after CAR-T cell treatment.

Conclusions: our results showed that CAR-T cell treatment could be safely administered in patients with Concomitant Hepatitis B Virus infection. Considering the small group sample size and retrospectively analysis, the risk of HBV reactivation with prophylactic entecavir treatment after CAR-T cell treatment should be further evaluated in large and prospective studies.

[Patient clinical characteristics before and after chimeric antigen receptor T cell therapy]

[Figure1. Time points of HBV detection and response after CAR-T cell treatment]

Clinical Trial Registry:

ChiCTR-ORN-16008948

ChiCTR-OIC-17011310

ChiCTR1800015575

ChiCTR1800017404

The website is http://www.chictr.org.cn

Disclosure:

Nothing to declare.

¹Mayo Clinic, Jacksonville, FL, United States, ²Mayo Clinic, Rochester, MN, United States, ³Mayo Clinic, Phoenix, AZ, United States, ⁴Mayo Clinic, Rochester, FL, United States

Background: Cytopenias occur frequently after axicabtagene ciloleucel (axi-cel), a recently approved anti-CD19 CAR-T cell therapy. The direct cause(s) of cytopenia (s) remains elusive. Rituximab has been associated with delayed onsent cytopenia in patients with non-Hodgkin lymphoma. Here, we investigate the impact of various patient- and pre-CAR-T treatment related factors including cumulative rituximab exposure, prior lines of treatment and prior auto-HCT on the persistence of cytopenia (s) in the setting of axi-cel.

Methods: We conducted a retrospective analysis of patients treated with axi-cel across three Mayo Clinic campuses (Rochester, Jacksonville, and Phoenix) from June 2016 until October 2019. Five patients received axi-cel in a clinical trial. The primary objective of this analysis was to identify factors associated with persistent cytopenias (leukopenia and thrombocytopenia) at day +90 in axi-cel recipients. Leukopenia was defined as less than 3 x10⁹/L and thrombocytopenia as a less than 100 x10⁹/L. Univariate analysis was used to analyze predictors and outcomes.

Results: A total of 57 patients, males (n=41, 72%), who had received a median of 3 (2-8) prior lines of therapy received axi-cel. Seventy three percent of patients (33/45, 12 patients had missing data) experienced at least a grade 1 cytopenia per CTCAE v5.0 at day+90. Twenty-four patients had failed a prior autologous transplant. The median number of prior rituximab doses was 8 (2-19). Pertaining to day +90 persistent leukopenia, age (≤ 52 vs. > 52 years, p=0.75), gender (p=0.72), number of prior therapies (p=0.80), a prior auto-HCT (p=0.66), and cumulative doses of rituximab (p=0.51) were not significant variables. None of these factors was predictive of persistent neutropenia (defined as less than 1.5 x10⁹/L) by day +90 post axi-cel. Pertaining to day +90 persistent thrombocytopenia, age (≤ 52 vs. > 52 years, p=0.3), gender (p=0.1), number of prior therapies (p=0.06), a prior auto-HCT (p=0.54), and cumulative doses of rituximab (p=0.06) were not significant variables.

Conclusions: Our analysis did not identify rituximab or any other patient- or pre-CAR-treatment related factors to be associated with persistence of leukopenia and thrombocytopenia at day +90 post axi-cel.

[Table 1]

Disclosure: YL declare.d the following conflicts of interest:

Research funding: Janssen, Merck, Kite/Gilead, Celgene, BlueBird Bio, Takeda

Consulting: Janssen, Legend BioTech, JUNO, Celgene, BlueBird Bio, Kite/Gilead, Novartis, Gamida Cells, AlloGene.

DSMB: Sorrento

Steering committee: Celgene, Janssen, Legend Biotech

MAK-D: consultancy for Daiichi Sankyo

Remaining authors disclose no relevant conflicts of interest.

Hannover Medical School, Hannover, Germany

Background: Reconstitution of lymphocyte subsets following lymphodepletion and chimeric antigen receptor (CAR) T cell infusion is pivotal for pathogen control. Moreover, lymphocyte subsets are thought to support CAR T antitumor activity. In this prospective single center pilot study we aim to investigate whether failure of anti-CD19-CAR T cell (Tisagenlecleucel) response one month post infusion is associated with a specific lymphocyte subset phenotype.

Methods: Blood samples of eleven patients with relapsed or refractory transformed follicular lymphoma and diffuse large B cell lymphoma (DLBCL) were examined by multi-color flow cytometry. Following lymphodepletion with fludarabine and cyclophosphamide, all patients received Tisagenlecleucel. The institutional review board approved the study and all patients gave written informed consent for prospective immune cell monitoring. Lymphocyte subsets were detected from peripheral blood using a 10-color antibody mix for T, B, and NK cell subsets as well as activation markers via flow cytometry. For determination of absolute frequencies BD Trucount™ tubes were used. Treatment response to anti-CD19-CAR T therapy was assessed via PET-CT one month post infusion.

[Figure 1: Analysis of lymphocyte subsets in responders (R) vs. non-responders (NR) at day +28.]

Results: Blood samples and PET-CT data were available on 9 out of 11 patients one month post infusion of Tisagenleclucel. Disease progression or no response to therapy was observed in 3 patients, termed non-responders (NR). The remaining 6 patients, termed responders (R), all showed reduced PET activity, with two (33%) achieving complete metabolic remission and four (66%) achieving partial metabolic remission. We compared different lymphocyte subsets in non-resonders vs. responders on day +28 (range 11-34). Interestingly, non-responders displayed higher relative frequencies and absolute numbers of CD8+ and CD3+CD56+ cells and fewer CD3-CD56+ cells compared to responders, albeit lacking statistical significance, likely due to the small sample size (Figure 1A and B). Moreover, CD4:CD8 ratio was markedly lower in non-responders (0.53 vs. 2.73), implying a shift in immune response. Further analysis of activation markers in conventional CD4+ (CD4_conv) and CD8+ cells revealed a trend towards decreased central memory populations in non-responders (Figure 1C and D).

Conclusions: Immune cell monitoring of lymphocyte subsets in CAR T cell patients may provide important insights in immune function supporting CAR T cell activity. In this prospective single center pilot study we describe an altered lymphocyte subset phenotype in patients failing to respond to Tisagenlecleucel. The phenotype consisted of a reduced CD4:CD8 ratio, lower CD3-CD56+ frequencies and central memory populations together with higher CD8+ and CD3+CD56+ populations. However, these data are limited by the small cohort size and warrant further validation in a larger cohort.

Disclosure: Nothing to declare.

Medizinische Hochschule Hannover, Hannover, Germany

Background: Treatment with CD19 chimeric antigen receptor (CAR) T cells represents a novel treatment approach for patients with relapsed or refractory diffuse large B cell lymphoma (r/rDLBCL) or B-lineage acute lymphoblastic leukemia (ALL). However, impressive therapeutic response rates are often accompanied by specific and severe toxicities. Besides the common cytokine release syndrome (CRS) which is characterized by fever, hypotension, hypoxia, and in more severe cases multisystem organ dysfunction, specific neurotoxicity termed immune effector cell-associated neurotoxicity syndrome (ICANS) has been observed as well and is treated as a separate entity with distinct timing and treatment requirements. Although symptoms can be more diverse than those of CRS, many patients with neurotoxicity show specific clinical features with expressive aphasia being one of the most characteristic ones.

Methods: Eleven r/rDLBCL patients have been treated with Tisagenlecleucel at Hannover Medical School between April 2019 and November 2019. All patients received an extensive neurological examination prior to CAR T cell infusion. This included clinical examination, handwriting sample, cognitive testing (Montreal-Cognitive-Assessment (MoCA)), brain magnetic resonance imaging (MRI), electroencephalogram (EEG), electroneurography (ENG), and analysis of cerebrospinal fluid (CSF) in 8/11 patients. After CAR T cell infusion, patients were neurologically examined for 10 consecutive days. Up to 4 weeks following infusion, we assessed all patients at least once a week.

Results: Baseline clinical neurological examination and ENG showed signs of axonal polyneuropathy in 10 of 11 patients before CAR T cell therapy indicating damage due to prior chemotherapy. Two patients presented with slightly impaired MoCA-results (25/30 points) and 1 patient achieved only 23/30 points prior to CAR T cell treatment. Brain MRI was unremarkable in all cases. CSF did not show signs of inflammation in all 8 patients (cell count 1-3/µl, oligoclonal bands negative) and no relevant disturbance of the blood-CSF-barrier (Qalbumin 4.7-8.5). No one exhibited antineuronal or autoimmune encephalitis antibodies. During the four-week follow-up period one patient developed a severe CRS at day 5 accompanied by mild signs of cognitive impairment (MoCA minimum 23/30), but without abnormalities in brain MRI. He died on day 23 following CAR T cell therapy due to infection. Two patients exhibited signs of cognitive impairment at day 4 and 5, respectively. Both patients showed very similar symptoms including apraxia, expressive aphasia, disorientation, and hallucinations. Symptoms developed very quickly, while brain MRI was inconspicuous in either case. Grade 2 ICANS was assumed in both patients and both were treated with dexamethasone 40 mg/d. As symptoms rapidly resolved steroid treatment was quickly tapered and stopped after 5 days. Both patients showed neither signs of cognitive nor neurological impairment afterwards.

Conclusions: Neurotoxicity is a feared complication of CD19 CAR T cell therapy and initial symptoms can be very subtle. Our longitudinal examinations in 11 patients revealed specific clinical symptoms of ICANS in 2 patients without relevant radiological abnormalities. Further studies with higher numbers of patients including a structured and detailed neurological examination are required to uncover CD19 CAR T cell-related neurotoxicity and its especially pathogenesis.

Disclosure: Nothing to declare.

Kings College Hospital NHS Foundation Trust, London, United Kingdom

Background: Chimeric antigen receptor (CAR) T-cell therapy targeting CD19 has demonstrated efficacy in the treatment of relapsed and refractory B cell non-Hodgkin lymphoma. In haematological cancers, nutrition is a concern, particularly in patients undergoing high dose therapies and haemopoietic stem cell transplantation (HSCT). The high-dose radiotherapy/chemotherapy associated with treatment and its typical spectrum of side effects, including nausea, vomiting, mucositis, diarrhoea and infections, further impacts oral food tolerance. This contributes significantly to weight loss (WL), particularly in the first 40 days of admission. As of yet, there have been no reports on the effects of CAR T-cell therapy on nutritional status.

The aim of this study is to report on the nutritional status of patients undergoing CAR T-cell therapy for CD19 positive non Hodgkin lymphoma, both prior to, and during their approximate 3-4 week inpatient admission for treatment.

Methods: 40 patients who underwent treatment between January and October 2019 had a comprehensive nutritional assessment prior to receiving CAR T-cell therapy. Of these patients, 39 had diffuse large B cell lymphoma and one patient mediastinal B cell lymphoma. They were reviewed during their inpatient admission stay and symptoms which impair nutritional intake (e.g. diarrhoea, poor appetite) were monitored, as well as WL and their requirement for oral, enteral and parenteral nutritional interventions.

Results: 25% of patients were identified as malnourished prior to treatment with poor nutritional status typically being related to pre-existing chronic illness e.g. inflammatory bowel disease or disease involving the GI tract. 38 patients were nutritionally assessed as inpatients in the 3-4 weeks after infusion of CAR T-cells. During this period, no significant impact on body weight (5% or more WL) was observed in 66% of patients who underwent therapy. This is hypothesised to be due to the reduced observation of side effects such as vomiting, diarrhoea and mucositis, which are frequently observed with other treatments for haematological cancers, in particular HSCT.^. Significant WL during this period (>10% of body weight) was observed in 8% (n=3) of patients.

50% of patient’s required nutritional supplements to meet their requirements and prevent unintentional WL during their admission. 18% (n=7), including all patients who suffered neurotoxicity required a period of enteral feeding via nasogastric tube. In the other 3 cases, nasogastric tube feeding was indicated due to severe anorexia/malnutrition or dysphagia due to disease being localised to the neck region.

Conclusions: CAR T-cell therapy appears to have a less significant impact on nutritional status than other similar treatments for haematological malignancies, primarily due to a lower incidence in adverse effects. However, all patients undergoing treatment should be nutritionally screened prior to treatment due to the high incidence of malnutrition in this population group. Patients who experience neurotoxicity are also at high risk of malnutrition and are likely to require nasogastric enteral feeding for a period to prevent significant WL. Further research on the impact of neurotoxicity on nutritional status, and longer term follow up on the nutritional impact of CAR T-cell therapy is required to influence future dietetic practice in this field.

Disclosure: Nothing to declare.

Universität Köln, Köln, Germany

Background: Chimeric antigen receptor (CAR) T-cell therapy is a novel and promising cellular treatment modality for a variety of malignancies. So far, it is mainly being used in haematological malignancies including relapsed or refractory high-grade lymphoma, acute lymphoblastic leukemia (ALL) and multiple myeloma. An autologous leukapheresis product is collected as source material for the CAR T-cell manufacturing process. This cohort of patients is typically heavily pre-treated, cytopenic and presenting significant disease- or treatment related complications. The effectiveness and feasibility of leukapheresis procedures in this setting was analysed.

Methods: In this retrospective analysis, 66 leukapheresis collections from patients participating in CAR T-cell clinical trials or from patients in preparation for CAR T-cell treatment with tisagenlecleucel in the commercial setting were reviewed. Collections were performed on the COBE Spectra apheresis device by experienced nurses. Pre-apheresis peripheral blood counts, apheresis parameters, and product cell counts were analysed.

Results: Patients with relapsed or refractory diffuse large B-cell lymphoma including Richter’s transformation (n=57), ALL (n=1), mantle cell lymphoma (n=3), follicular lymphoma (n=1) underwent leukapheresis collection for CAR T-cell production. Median age of the patients was 60 years (range 20-83). The median body weight of the patients was 73kg (range 39-137). Median pre-collection CD3 and lymphocyte counts were 540/µl (range 30-3400) and 620/µl (range 90-4960), respectively. The median pre-collection leukocyte count was 5240/µl (range 700-52650) and the median hematocrit was 30% (range 18-44). A median number of 3,92 x10e9 CD3+ T-cells was collected (range 0,2-18,23 x10e9) by processing a median number of 2,1 total blood volumes (range 0,4-3,8). This corresponds to a collection of 0,37x10e9 CD3+ T-cells per liter blood processed. The collection efficiency was 60% (CE2). Only one patient failed to collect sufficient T-cells, in this case in the context of massive tumor progression and infection. Two patients had to be collected twice on consecutive days. Vascular access was a central line in 32 and a peripheral vein in 34 procedures. Leukapheresis was well tolerated in all cases.

Conclusions: Our data demonstrates that a standard leukapheresis is effective to collect sufficient CD3 T-cells for CAR T-cell production. Patients can be safely and successfully collected with CD3 counts down to 50-100 CD3 T-cells/ µl peripheral blood. Follow-up of completed infusion rates and reasons for infusion failure are currently under investigation and will be presented.

Disclosure: The authors have no conflict of interest to disclose.

Tel Aviv Medical Center, Tel Aviv University, Tel Aviv, Israel

Background: CAR-T (Chimeric Antigen Receptor Therapy) has become an acceptable therapy option in patients with chemo-refractory DLBCL. Patients in most cases have a rapidly progressive disease hence the CAR-T process should follow a very strict time course to ensure high percentage of patients receiving the final product, while maintaining patents’ safety and product integrity. We aim to develop a clinical and quality management system to ensure the overall success of the procedure.

Methods: We established a system to allow a CAR-T team to self-assess against a group of standard guidelines/procedures. This system will serve as a control process to review, analyse, implement and improve suboptimal results. All subprocesses of the CAR-T were identified and individually dissected into different parameters based on the CARTangle - our unique centre model based on 3 domains - patient, disease and logistics. Subprocesses and domains are prospectively monitored for defined endpoints, flaws, deviations and events, corrective actions and change control procedures are then implemented, when indicated.

Results: The following subprocesses were defined - 1. Referral of a patient and eligibility criteria for the CAR-T program, 2. Bridging to apheresis, 3. Bridging to infusion, 5. infusion of the product and short-term follow-up, and 6. Long-term follow-up. The correspondence clinical and quality management parameters are defined below (Table). Data of enrolled patients with the corresponding quality management parameters will be presented at the meeting.

Conclusions: This pivotal clinical and quality management system is an ongoing process and is obliged to maximize patients and products´ safety and performance.

Disclosure: Nothing to declare.

¹AORN Santobono-Pausilipon, Naples, Italy, ²Univeristy of Texas MD Anderson Cancer Center, Houston, TX, United States

Background: Extra-medullary ALL develops in sanctuaries including, CNS, genitourinary and “sequestered sites” (gut, breast, skin). Data regarding complete remission (CR) rates and durability of response among patients receiving CART with relapsed/refractory (r/r) ALL and extra-medullary disease is still emerging.

Methods: We report two AYA patients with r/r ALL and extra-medullary involvement who achieved CR after tisagenlecleucel.

Results: Patient 1 was refractory to 7 prior lines of therapy and developed CNS, liver, spleen and bilateral kidney involvement; He experienced CD19 negative relapse approximately 8 weeks later. He subsequently achieved CR following two doses of inotuzumab and then received a reduced intensity (RIC) related haplo-identical SCT. He experienced a CNS relapse approximately 2 months later and died shortly after. Patient 2 had isolated bilateral breast involvement following allogeneic stem cell transplantation (SCT). She experienced swelling and erythema of the breast tissue following CART and achieved MRD negative CR in the bone marrow with partial response in the breast. She subsequently received XRT to the breast and was consolidated with a RIC SCT. She died approximately 100 days post-SCT from sepsis.

Conclusions: The majority of 53 reported patients with ALL and extra-medullary breast involvement (22 occurred post-SCT) received combined radiation and chemotherapy; 4 received DLI and achieved CR but 2 died of severe GvHD. CAR-T cells, may likewise circulate and act in sequestered sites but without GvHD. Lympho-depletion preceding CAR-T may also eliminate regulatory T lymphocytes and potentially enhance the immune response. Combined treatment with CAR-T and radiation may help eradicate extra-medullary disease, taking advantage of the local death of dividing cells with radiation with potential enhancement of the microenvironment to facilitate CAR-T function and enhance anti-tumor immune response of resident T cells. Future studies will elucidate the optimal timing of CART among patients with extra-medullary disease, which may improve durability of response and long-term outcomes.

Disclosure: Nothing to declare.

University of Leipzig Medical Center, Leipzig, Germany

Background: CAR T-cells directed against CD19 are a newly approved cellular therapy for treating patients (pts) with relapsed or refractory (r/r) pediatric and adolescent acute lymphoblastic leukemia or diffuse large B-cell lymphomas (DLBCL). Given the aggressive nature of the underlying diseases bridging pts from lymphapheresis (LA) to CAR T-cell infusion remains a challenging task. Very little is known on factors predicting successful bridging pts during this period in the real world population.

Methods: We evaluated clinical variables potentially affecting successful re-infusion of CAR T-cells in pts receiving CD19 CAR tisagenlecleucel at our CAR T-cell center.

Results: Ten pts were assigned to CAR T-cell therapy and underwent LA between May to August 2019 for r/r DLBCL. 3 pts died prior to infusion. 7 pts received CAR T-cells after a median time of 49 days after LA. Pts receiving the CAR T-cells presented with lower lactate dehydrogenase (LDH) and C-reactive protein (CrP), better ECOG performance score (PS) at the time of LA and had received fewer lines of therapy than patients not receiving CAR T-cells. We developed a scoring system, which included the mean LDH (>8.3 µkat/l) and CrP (>90 mg/l) at the time of LA forpatients that did not receive the CAR T-cells (2 points each), ECOG PS (1 point per ECOG PS), lines of therapy after 1^st salvage (1 point per line) and referral from an external hospital (1 point) in order to predict outcome. All but one patient receiving the CAR T-cells had a score of < 5.

Conclusions: Bridging eligible patients from LA to CD19 CAR T-cell infusion remains a challenge. Patients with a CAR T score >4 should be considered to be at higher risk for complications. The proposed score has to be evaluated in a larger cohort.

Disclosure: Franke: Novartis, Pfizer, Jazz, MSD, Takeda: Honorary. Gilead: travel support

Vucinic: Novartis, Gilead, Takeda, Abbvie: Honorary

¹CHU Lille, Lille, France, ²University of Lille, Lille, France, ³LIRIC, INSERM U995, Université de Lille, Lille, France

Background: CAR T-cells (CARTc) are patient T-cells that express artificial chimeric antigenic receptors (CAR) capable of recognizing tumor cells antigen. Axicabtagene ciloleucel is indicated in patients with relapsed diffuse large B-cell lymphoma or those who are refractory to other treatments. A medication reconciliation activity has been carried out since the beginning of 2019. The objective is to assess the value of medication reconciliation at admission of patients receiving CARTc.

Methods: A medication reconciliation have been conducted by pharmacy students under the supervision of pharmacists for patients receiving CARTc. A medication history, including self-medication treatments, has been established according to at least 3 information sources. Intentional or unintentional discrepancies were underlined for each difference between the medication history and the first medical prescription at admission. Pharmaceutical interventions (PI) resulted from a discrepancy. Medication adherence was assessed according to the medication adherence scale of our national insurance system. Patients were considered: good, minimal or not adherent. In parallel, allergies and medication difficulties were reported. Data were prospectively recorded anonymously on an Excel^® datasheet.

Results: Between January 3^rd and October 30^th, 2019, 30 patients received CARTc. The age was 60±10 years and gender ratio was 0.7. Patients received 4±2 previous lines of treatment. Reconciliation could have been performed in 18 patients. They took an average of 6 medications ([1; 19]), notably anti-infectious prophylaxis: valaciclovir (N=12/18) and co-trimoxazole (N=9/18). Intentional discrepancies (N=93) and unintentional discrepancies (N=8) were found. Six PI were formulated, and 5 accepted: 1 discontinuation of lansoprazole (no indication found), 1 dose adjustment for irbesartan, 1 dosage error for morphine, 2 missed treatment continuations (pravastatin and isradipine). Patients were considered good adherent (N=4/18), minimal adherent (N=12/18) and not adherent (N=2/18). The main reasons for low adherence were notably: too many tablets to take, forgetfulness, and delays. No patients had any trouble for drug intake. Acetaminophen was the main self-medicating drug.

Conclusions: During the study period, some patients were not reconciled due to a lack of staff in the department, particularly at the beginning of the year. Usually, the studied population takes few drugs. Therefore, some patients took more than 10 drugs. In this study, drug adherence was often minimal as shown in a literature review that evaluates drug adherence in patients receiving hematopoietic stem cell transplantation¹. This shows that reconciliation activity for these patients appears essential in order to review treatments, insist on medication adherence and to prevent the risks of drug-drug interaction, especially with the conditioning regimen. The data from this preliminary study need to be confirmed on a larger population.

¹ Morrison CF, Martsolf DM, Wehrkamp N, Tehan R, Pai ALH. Medication Adherence in Hematopoietic Stem Cell Transplantation: A Review of the Literature. Biology of Blood and Marrow Transplantation. avr 2017;23(4):562-8.

Clinical Trial Registry: /

Disclosure: /

CAR-based Cellular Therapy – preclinical

¹Dr. von Hauner Children’s Hospital, Medical Center of the University of Munich, Munich, Germany, ²National Center for Translational Oncology Research (DKTK), Munich, Germany, ³Medical Center of the University of Munich, Ludwig-Maximilians University Munich, Member of the German Center for Lung Research, Munich, Germany, ⁴Max-Eder Research Group for Pediatric Sarcoma Biology, Ludwig-Maximilians University Munich, Munich, Germany, ⁵Stanford University, Stanford, CA, United States, ⁶Technical University Munich, Munich, Germany, ⁷National Center for Infection Research (DZIF), Munich, Germany

Background: Therapy with autologous T cells expressing an anti-CD19 chimeric antigen receptor (CAR) has been recently approved for patients with B-cell lymphoma and B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Despite tremendous success in pediatric BCP-ALL, 40 to 50% of the patients do not experience long-term relapse-free survival after CAR T-cell treatment. Allogeneic stem cell transplantation (allo-SCT) is offered to selected patients after CAR treatment to prevent relapse.

Methods: To increase functionality of conventional anti-CD19 and anti-CD22 CAR T cells pre allo-SCT and protect the T cell from leukemia-mediated inhibition, a PD-1/CD28 fusion receptor was designed. Fusion receptors convert an inhibitory signal into an intracellular activation cascade. PD-1/CD28 anti-CD19 and anti-CD22 CAR T cells were functionally characterized and compared to conventional CAR T cells in terms of cytotoxic capacity, proliferation, activation and cytokine release after single and multiple contact with leukemic cells.

Results: The impact of prominent co-inhibitory immune checkpoint axes (such as PD-1/PD-L1) for relapse or non-response to CAR T-cell therapy is not yet fully understood. Bone marrow analyses of >100 BCP-ALL patient samples pre allo-SCT showed substantial heterogeneity in initial PD-L1 expression levels of leukemic blasts and the ability to up-regulate PD-L1 upon T-cell attack. Cytokine release of conventional 2^nd generation anti-CD19 CAR T cells was significantly reduced after contact with a PD-L1 overexpressing ALL. We hypothesized that a PD-1/CD28 fusion receptor can increase functionality of conventional CAR T cells while protecting the T cell from leukemia-mediated inhibition. Anti-CD19 CAR T cells with PD-1/CD28 fusion receptors were generated and showed strong CD19-dependent cytotoxicity, proliferation, activation and cytokine release. No unspecific cytokine release mediated by the fusion receptor in absence of CD19 was detected. In presence of PD-L1, fusion receptor CAR T cells out-competed conventional 1^st and 2^nd generation anti-CD19 CAR T cells and released significantly higher levels of Th1 cytokines IFN-γ, IL-2 and TNF-α. PD-1/CD28 anti-CD19 CAR T cells were able to persist after >4-fold stimulation with leukemic cells and showed significantly increased long-term killing capacity and cytokine release compared to conventional CAR T cells after multiple stimulations. Superiority of CAR T cells with PD-1/CD28 fusion receptor was confirmed in an anti-CD22 CAR T cell model.

Conclusions: Anti-CD19 and anti-CD22 CAR T cells with PD-1/CD28 fusion receptor can increase functionality of conventional CAR T cells by circumventing leukemia-induced T-cell inhibition pre allo-SCT.

Disclosure: Nothing to declare.

¹Stanford University, Stanford, CA, United States, ²Geneva University Hospitals, Geneva University, Geneva, Switzerland, ³Stanford Cancer Institute, Stanford, CA, United States

Background: Chimeric antigen receptor (CAR) T cells have shown impressive results in B-cell malignancies but, unfortunately, their widespread use is still limited by the logistical and financial burdens related to the need of generating autologous cell products. The development of universal allogeneic CAR T cells to be used off-the-shelf has faced major limitations, namely the risk of Graft-versus-Host-Disease (GvHD) induction and the rejection of the cells by the host immune system. Invariant Natural Killer-T (iNKT) cells are innate lymphocytes deprived of GvHD induction potential and displaying antitumor effects, both directly and indirectly, through enhancement of CD8 T cell responses. Preclinical studies in xenogeneic mouse models demonstrated the feasibility of using iNKT cells as a platform for CAR-based therapies, and two clinical trials are currently ongoing. In this work, we assessed the immunoadjuvant effect of allogeneic CD19-specific iNKT CAR on the host immune system.

Methods: We transduced murine iNKT cells from FVB/N (H-2K^q) mice with a CD19-specific CD28/CD3ζ CAR and assessed their antitumor effect in vitro and in vivo.

Results: CD19-iNKT CAR had a direct cytotoxic effect in vitro against the CD19+ A20 lymphoma cells and significantly improved survival of mice after administration to major histocompatibility complex (MHC)-mismatched, immunodeficient BALB/c (H-2K^d) Rag2^-/- gamma-chain^-/- mice receiving A20 lymphoma cells (2x10e4; Figure 1A) without inducing any signs of GvHD. To test the efficacy of iNKT CAR cells in the presence of host immune cells, we employed BALB/c mice receiving sublethal irradiation (4.4 Gy), resulting in only a partial and transient lymphopenia. The antitumor effect of allogeneic iNKT CAR cells was greatly enhanced suggesting the participation of host cells in the antitumor effect. Interestingly, the iNKT CAR effect was partially abrogated when we employed as recipients BALB/c BATF3^-/- mice, in which CD8 T cell cross-priming is impaired as a result of the absence of BATF3-dependent CD103+ CD8a+ dendritic cells known to play a role in iNKT cell interactions with other immune effector cells. Moreover, co-administration of allogeneic FVB/N iNKT CAR with autologous BALB/c CD8 T cells at the time of transfer of T-cell-depleted autologous bone marrow cells and A20 cells into lethally irradiated BALB/c recipients resulted in a synergistic effect. To prove the induction of tumor specific CD8 T cell responses, host CD8 T cells were isolated at day 60 from sublethally irradiated BALB/c mice receiveing A20 cells and treated with iNKT CAR. CD8 T cells primed in the presence of iNKT CAR transferred into new lethally irradiated recipients receiving A20 cells and BM from syngeneic Rag2^-/- gamma-chain^-/- mice significantly increased survival. Due to their immuno-adjuvant effect on host CD8 T cells, low numbers of allogeneic iNKT CAR outperformed allogeneic conventional CAR T (Tcon CAR) when administered to sublethally irradiated BALB/c mice receiving A20 cells.

Conclusions: Collectively, these results demonstrate the potent immunoadjuvant effect exerted by allogeneic iNKT CAR cells toward the host immune system suggesting that iNKT CAR cells are an attractive off the shelf product for adoptive immunotherapy.

Clinical Trial Registry: N/A

Disclosure: Nothing to disclose

¹Hospital Universitario 12 de Octubre, Spanish National Cancer Center, Madrid, Spain, ²Hospital Universitario 12 de Octubre, Madrid, Spain, ³Research Center for Energy, Environment and Technology, Madrid, Spain, ⁴Vivia Biotech, Madrid, Spain, ⁵Spanish National Cancer Center, Madrid, Spain, ⁶Hospital Universitario La Paz, Madrid, Spain, ⁷The Research Institute At Nationwide Children’s Hospital, Columbus, OH, United States, ⁸University of Pennsylvania, Philadelphia, PA, United States

Background: Chimeric antigen receptor (CAR) therapy is showing promising results in hematological malignancies. Since AML exhibits high heterogeneity and does not have specific differential antigens of the hematopoietic stem cell, using NKG2D-CAR cells could be an appropriate therapeutic strategy against AML. NKG2D receptor has a wide range of specific tumor cell ligands expressed in more than 80% of all tumors. Here we evaluate the anti-tumor activity of activated and expanded natural killer cells (NKAE) and T cells expressing an NKG2D CAR.

Methods: T cells and NK cells were isolated from the healthy donor´s PBMCs (n=5). NKAE cells were obtained by co-culture with subletally irradiated CSTX002 cells. Then, NKAEs and T cells were transduced with an NKG2D CAR. The efficiency of transduction was evaluated by flow cytometry. The cytotoxicity and toxicity on healthy tissues was evaluated by 4 hour europium release assay. The safety of NKG2D-CAR transduced cells was evaluated using CGH arrays.

Results: Both the AML cell lines and primary blasts from AML patients showed expression of the MICA/B and ULBPs-1 to 3 ligands (high expression of at least 3 of the 5 analyzed ligands). Four hour europium release assays revealed that untransduced T cells had higher cytotoxicity than untransduced NKAE cells at the same ratio (32:1) against both OCI-AML-3 cytarabine-resistant cell line (52.7% ± 14.2% vs. 32.5% ± 7.2%) as to the cytarabine-sensitive cell line (56.42% ± 5.6% vs. 50.14 % ± 5.9%). T cells showed a better transduction efficiency than NKAE cells at a multiplicity of infection (MOI) of 5. It was observed that both the CAR-NKAE cells and the CAR-T cells had higher cytotoxicity against these two lines (OCI-AML-3R and OCI-AML-3S) after being transduced with our NKG2D-CAR. However, the antitumor activity of CAR-T cells always remained superior to that of the CAR-NKAE for both OCI-AML-3R (54.26% ± 3.8% vs. 35.3% ± 6.7%) and for OCI-AML-3S (63.36% ± 3.5% vs. 54.3% ± 3.7%) cell lines, with a greater difference compared to drug resistant cells. The antitumor activity of CAR-T cells and CAR-NKAE cells was always superior on the sensitive cell line. The antitumor activity of NKG2D CAR-T cells was evaluated against primary blasts from AML patients (n = 4), observing a nearly complete destruction of the blasts after 24 hours, at low target: effector ratio (4:1). CAR-T cells were highly positive to CD45RO and showed reduced expression of CD45RA. They showed high IL-2 production exhibiting a central memory phenotype. CAR-T cells exhibited some toxicity on third party PBMCs being null in the case of CAR-NKAE. CGH arrays studies showed no variation in the copy number, resulting from the introduction of the CAR. In vivo studies are ongoing.

Conclusions: AML cells could be target with an NKG2D-CAR. Primary NKAE cells and T cells can be transduced with an NKG2D-CAR at a very low MOI to enhance their antileukemic activity. CAR-T cells were able to completely destroy AML blasts. Although further studies are needed, these results show the potential of NKG2D-CAR T and NK cell therapy in AML.

Disclosure: Dean A. Lee declare.s an equity interest, advisory role, and intellectual property licensing to CytoSen Therapeutics and Kiadis Pharma, and advisory role with Caribou BioSciences and Courier Biosciences. Daniel J. Powell Jr. hold patents in the area of CAR T cell therapy. Rest of the authors have nothing to declare.

¹Universitätsklinikum Würzburg, Würzburg, Germany, ²Fraunhofer-Institut für Zelltherapie und Immunologie, Leipzig, Germany, ³Max-Delbrück-Centrum für Molekulare Medizin, Helmholtz Gemeinschaft, Berlin, Germany

Background: Immunotherapy with T-cells that were modified to express a ROR1-specific chimeric antigen receptor (ROR1 CAR-T) has therapeutic potential in ROR1⁺ malignancies in hematology and oncology. In toxicology studies in non-human primates, the adoptive transfer of ROR1 CAR-T did not disclose relevant clinical toxicity, encouraging the initiation of clinical trials to assess the safety and efficacy of ROR1 CAR-T therapy in patients with advanced ROR1⁺ malignancies. In this study, we sought to establish and validate clinical-grade manufacturing of ROR1 CAR-T to enable a Phase I/IIa clinical trial. In particular, we sought to integrate virus-free gene-transfer based on Sleeping Beauty transposition into this manufacturing protocol to easily permit scale-up, and to reduce the regulatory burden associated with conventional viral gene-transfer.

Methods: Buffy coats or leukaphereses were obtained from healthy donors to perform protocol optimization (n=7) and scale-up runs (n=1). CD4⁺ and CD8⁺ T cells were isolated separately and stimulated with CD3/CD28 TransACT reagent (Miltenyi). T cells were transfected with mRNA encoding hyperactive Sleeping Beauty transposase (SB100X) and minicircle DNA encoding a pT2 transposon comprising the ROR1 CAR and an EGFRt marker gene using the MaxCyte GTx electroporation platform. Following transfection, T cells were expanded for 10-13 days in G-REX bioreactors and then harvested and formulated into the drug product at a 1:1 ratio of CAR-expressing CD4:CD8 T-cells. The drug product underwent comprehensive phenotypic, functional and genomic analyses as part of product qualification.

Results: The set of protocol optimization runs provided insights into the optimal timing between T-cell activation and transfection, as well as the amount of SB100X mRNA and ROR1 CAR minicircle DNA for transfection into the T-cells. On average, the stable gene-transfer rate at the end of the manufacturing process was 71% in CD4⁺ (n=5) and 54% in CD8⁺ T-cells (n=7). The average yield of CAR-expressing T-cells relative to the number of input T-cells was 12.6-fold for CD4⁺ and 9.4-fold for CD8⁺ after 12-15 days of expansion, with an average viability of 84% for CD4⁺ and 82% of CD8⁺ T-cells. The set of scale-up runs was performed with leukapheresis product from which 70x10^6 CD4⁺ T-cells and 130x10^6 CD8⁺ T-cells were further processed. At the end of the manufacturing process on day 12, there were 844x10^6 CAR-expressing CD4⁺ and 857x10^6 CAR-expressing CD8⁺ T-cells, which equals a 16-fold and 7.9 fold expansion relative to the input T-cell number, respectively. Overall, ROR1 CAR-T showed specific recognition and potent elimination of ROR1⁺ target cells, as well as antigen-dependent cytokine production and productive proliferation. Experiments to determine the anti-tumor potency of the drug product in vivo and detailed genomic analyses are ongoing.

Conclusions: With this novel protocol, we aim to obtain the first manufacturing license for CAR-T in Europe that integrates our optimized approach with SB100X mRNA and transposon minicircle DNA for CAR gene-transfer on the MaxCyte transfection platform. The quality and yield of the drug product support the design and dose escalation of the proposed clinical trial with ROR1 CAR-T, and will serve as a blueprint for other CAR-T products from our pipeline.

Disclosure: Nothing to declare.

¹University Hospital Frankfurt, Goethe University, Frankfurt, Germany, ²University Hospital Frankfurt, Goethe University, Frankfurt, Germany, ³German Cancer Consortium (DKTK) partner site Frankfurt/Mainz, Frankfurt, Germany, ⁴Paul-Ehrlich-Institut, Langen, Germany, ⁵Fraunhofer Institute for Cell Therapy and Immunology (IZI), Leipzig, Germany, ⁶Hannover Medical School, Hannover, Germany, ⁷University Leipzig, Leipzig, Germany, ⁸Hannover Medical School, Hannover, Germany, ⁹Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States, ¹⁰Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, Frankfurt, Germany, ¹¹Frankfurt Cancer Institute, Goethe University, Frankfurt, Germany, ¹²Paul-Ehrlich Institut, Langen, Germany

Background: Autologous chimeric antigen receptor-modified (CAR) T cells with specificity for CD19 showed potent antitumor efficacy in clinical trials regarding relapsed and refractory acute lymphoblastic leukemia (ALL). Natural killer (NK) cells are cytotoxic lymphocytes that are capable to kill their targets in a non-specific manner and additionally do not cause GvHD. Therefore, using CD19-CAR-NK cells exhibits several advantages, such as safety in clinical use, possible allogenic settings and the potential to also attack heterologous leukemia cells which lost CD19. Here, we focused on the optimization of generating CD19-CAR-NK cells by viral transduction under feeder-cell free conditions.

Methods: Human NK cells were isolated from healthy donor peripheral blood mononuclear cells via CD56 negative selection. After a feeder-cell free expansion phase with interleukin 15 (IL-15), transductions were performed with a CD19-CAR encoding vector at different multiplicities of infection (MOI). To optimize gene modification different viral vector systems were compared using lentivirus and alpharetrovirus, pseudotyped with either VSV-G or RD114-TR. Finally, generated CD19-CAR-NK cells were tested in their ability to kill CD19-positive and CD19-negative cell lines.

Results: Transduction efficiencies of NK cells transduced with the RD114-TR pseudotyped alpharetroviral or lentiviral CD19-CAR vectors outperformed transduction with VSV-G pseudotyped lentiviral vector (lentiviral/RD114-TR: MOI 1: 10,9%, MOI 5: 24.0%, MOI 10: 27.3%; alpharetroviral/RD114-TR: MOI 1: 14.7%, MOI 5: 28.5%, MOI 10: 37.4%; lentiviral/VSV-G: MOI 1: 0.9%, MOI 5: 4.4%, MOI 10: 8.2%). As possible mechanism, dependent on IL-15, we observed a significant upregulation of the surface expression of ASCT-2 on the primary NK cells that is an entry receptor for RD114-pseudotyped vectors.

Remarkably, CD19-CAR-NK cells generated by RD114-TR pseudotyped retroviral vectors showed stable transgene expression and were able to expand almost as good as non-transduced (NT) NK cells over a time period of 14 days.

Independent of the transduction method, engineered CD19-CAR-NK cells showed an impressively high cytotoxic capacity against CD19-positive ALL cells compared to NT-NK cells; alpharetroviral/RD114-TR CD19-CAR-NK inducing 73.1% vs. lentiviral/RD114-TR CD19-CAR-NK cells inducing 74.7% vs NT- NK cells inducing 35.9% of cell death; E:T ratio 1:1 in 4 hours).

Conclusions: CD19-CAR-NK cells can be successfully generated under feeder-cell free conditions using different transduction enhancers and viral vector systems. Our data suggest the usage of Vectofusin-1 in combination with RD114-TR pseudotyped retroviral vectors to genetically modify NK cells to achieve sufficient amounts of highly cytotoxic transduced cells. These CD19-CAR-NK cells mediate high cytotoxicity and therefore may offer a new therapeutic option in the treatment of ALL. These insights will be transferable in CAR-NK-cell engineering to target different other malignancies.

Disclosure: Axel Schambach is an inventor on a patent describing alpharetroviral SIN vectors. Winfried S. Wels is an inventor on a patent describing chimeric antigen receptors with an optimized hinge region. The remaining authors have nothing to disclose.

¹imSAVAR Consortium, Würzburg, Germany, ²imSAVAR Consortium, Basel, Switzerland, ³imSAVAR Consortium, Stuttgart, Germany, ⁴imSAVAR Consortium, Enschede, Netherlands, ⁵imSAVAR Consortium, Maasmechelen, Belgium, ⁶imSAVAR Consortium, Leipzig, Germany

Background: Adoptive immunotherapy with gene-engineered CAR-T-cells is a transformative treatment in hematology but can be associated with significant toxicity from e.g. cytokine release syndrome (CRS). Preclinical testing to assess CRS is not standardized and there is a strong medical need and desire to establish algorithms to assess the propensity of novel CAR-T-cell products and technologies to induce CRS and other toxicity. imSAVAR - immune safety avatar - is an EU Innovative Medicines Initiative (IMI) project that tackles this challenge in a joint academia-industry consortium and seeks to establish a framework and platform for assessing the utility of innovative non-clinical models and endpoints for enhancing the safety assessment of e.g. CAR-T cells.

Methods: imSAVAR is pursuing a 4-step approach: Step 1 comprises a systematic literature review on pathophysiology and clinical occurrence of CRS after CAR-T-cell therapy. Step 2 comprises a survey amongst academia and industry stakeholders to identify current gaps of existing and emerging preclinical test systems that are used to assess CRS. Step 3 is an open multi-stakeholder workshop that also engages EU and US regulators and patients to determine a roadmap for studies that establish a new set of non-clinical assays and endpoints that will subsequently be validated for their ability to enhance hazard identification, provide mechanistic insight, and help mitigate clinical safety concerns in Step 4.

Results: In Step 1 imSAVAR established a new conceptual map of CRS pathogenesis as an immune-related adverse outcome pathway (irAOP) comprising key molecular events (CAR target antigen engagement, signaling and T-cell activation) and cellular events (CAR-T-cell migration to tumor site, engagement with tumor cells in an immune synapse, secretion of pro-inflammatory mediators, activation of tissue resident and endothelial cells, and systemic inflammation). To each of these events, existing and emerging pre-clinical assays were allocated. In Step 2, a pilot survey was conducted with n=3 CAR-T-cell products from within the consortium. Encouragingly, the repertoire of novel test systems available in imSAVAR for evaluating CAR-T mediated cytokine release include in vitro co-culture assays of CAR-T with tumor cells, single-cell resolution molecular endpoints, in vivo humanized mouse models (e.g. NSG-3G) as well as microphysiologic organ-on-a-chip models. imSAVAR is preparing an open survey to collect data from n≥10 CAR-T and n≥10 other immune-oncology products to inform the research roadmap. All data will then be normalized and correlated with clinical data to identify optimal pre-clinical assays for enhancing the assessment and prediction of CRS.

Conclusions: imSAVAR has established an irAOP that will enable the development and validation of novel non-clinical assays that aim to enhance the characterization of CAR-T-cell associated cytokine release during pre-clinical development. This effort is ultimately anticipated to enhance the safety assessment of therapeutic CAR-T products, thus potentially accelerating patient access to CAR-T products with an enhanced therapeutic index. This CAR-T irAOP strategy forms part of imSAVAR’s broader efforts to enhanced non-clinical safety assessment algorithms for additional immunomodulatory therapeutic modes-of-action (e.g. TCR-transgeneic T cells, bi-specific T-cell engaging antibodies; checkpoint inhibitor antibody combinations; Treg modulators), and a range of immune system-related toxicities (e.g. ICANS, infections).

Disclosure: Nothing to declare. This project receives funding from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 853988.

¹Basque Center for Blood Transfusion and Human Tissues, Galdakao, Spain, ²Biocruces Bizkaia Health Research Institute, Barakaldo, Spain, ³CIC bioGUNE, Derio, Spain, ⁴Ikerbasque, Basque Foundation for Science, Bilbao, Spain, ⁵Hospital Galdakao-Usansolo, Galdakao, Spain, ⁶Hospital Clínic de Barcelona, Hospital Sant Joan de Déu, Institut d’Investigacions Biomèdiques August Pi i Sunyer Hospital, Universitat de Barcelona, Barcelona, Spain

Background: Among hematological cancers, Acute Lymphoblastic Leukemia (ALL) and Chronic Lymphocytic Leukemia (CLL) are the most common leukemia in children and elderly people respectively. Chimeric antigen receptor (CAR) therapy is one of the newest and more effective treatments against these cancers. CAR T cell therapy presents still some risks for the patients, including cytokine release syndrome (CRS) and neurotoxicity. We proposed NK cells from different cell sources for allogeneic CAR therapy.

Methods: 1. Enrichment and culture of NK cells from AB and CB. NK cells were isolated from AB or CB PBMCs by negative selection after magnetic cell isolation. Then, the NK cells were cultured with IL-2 and IL-15 for 8 days.

2. CD19-CAR lentiviral transduction to AB and CB NK cells

3. Functional assays facing CD19-CAR transduced and non-transduced AB and CB NK cells against CD19 expressing target cells. We measure CD107a marker in degranulation assays; and Calcein-AM released by target cells in cytotoxicity assays.

Results: 1. Percentage of the purity of the CD56+ NK cell population was 92.68±2.90 in AB and 91.46±5.14 in CB. NKp46 levels during the culture increase significantly from day 0 to day 7 in both cell sources. In fact, CB NK cells were significantly more stimulated than AB NK cells. We obtained more cells from the isolation from CB than from AB. During the first week, both sources expanded similarly; however, slightly higher fold expansion was observed after two weeks in CB NK cells

2. The mean AB CAR-NK transduction efficiency was 47.46 (range 62.6-20.2%; n=12) while CB CAR-NK transduction efficiency was 46.8 (range 79.7-18.1%; n=12). Seven days post-transduction the viability of AB and CB NK cells remained at 78.85% ± 10.18% and 76.2% ± 5.3%, respectively. In both cases, viability decreased over time until day 28. CAR expression shows a stable decrease of transduction from 40% to 20% with time as determined by flow cytometry every 7 days.

3. On one hand, when exposed to CD19 positive cells, AB CD19-CAR NK cells showed a significantly higher degranulation than non-transduced AB NK cells. On the other hand, when exposed to CD19 positive cells, CB CD19-CAR NK cells showed a significantly higher degranulation than non-transduced CB NK cells. We observed the same results when performing a cytotoxicity assay. AB CD19-CAR NK cells kill slightly better than CB CD19-CAR NK cells.

Conclusions: - CB NK cells present a more stable number of cells per unit than AB NK cells, and they can be stimulated with different interleukins in order to enhance the in vitro expansion, their killing activity and survival.

- Despite the difficulty of infecting NK cells, in our hands we obtain around 40-50% of infection with AB and CB NK cells with CD19-CAR.

- CD19 expressing target cells are killed more efficiently by AB and CB NK cells transduced with CD19-CAR than by non-transduced AB and CB NK cells.

CD19-CAR infected NK cells from AB and CB kill similarly CD19 expressing target cells. However, we observe a higher degranulation of the AB NK cells.

Disclosure: Nothing to declare.

Beijing Boren Hospital, Beijing, China

Background:

Philadephia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) is a distinct type of ALL, which has a high incidence of adult patients and a dismal poor prognosis. Resistance/relapse(r/r) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remain a significant challenge. Once relapsed, almost patients are resistant to the TKI because T315I mutation of ABL-kinase domain mution(AKDM).

Chimeric antigen receptor T-cells (CART) has shown a higher complete remission(CR)rate in r/r B-ALL patients and has a good security.

So we sequentially applied CART and TKI therapy to treat the Ph+ALL patients relapsed after allo-HSCT and observed the effect.

Methods: From January 1,2018 to June 31,2019, fourteen adult Ph+ALL patients relapsed after allo-HSCT were enrolled. CD19 and/or CD22 expression on blasts and AKDM were detected by flow cytometry(FCM) and polymerase chain reaction(PCR), respectively.

Recipient-derived donor T cells were collected and cultured CART cells, which were transfected by lentiviral vectors encoding the CAR composed of CD3zeta-4-1BB.

ALL patients received fludarabine with or without cyclophosphamide before CART cell infusion, some patients received othder chemotherapy or TKI based on the precondition because high disease burden or extramedullary disease (EMD). CART cell dose was 0.5-2×105/kg (CD19-CART) and 1-2.8×105/kg (CD22-CART). After CART cell

infusion, CART cell, cytokines were measured on D7, D9, D11 etc. and other days depending on the patient’s condition. We evaluated Bone marrow(BM) and cerebrospinal fluid (CSF)morphology, minimal residual disease(MRD)by FCM and BM BCR-ABL1fusion transcripts by real-time quantitative PCR(QPCR) on D30, EMD was examined by imaging examination and once every month later.

Once these patients acquired CR, TKI treatment was followed according to the AKDM and followed up to November 26,2019(6-22 months).

Results: Fourteen patients were aged 17 to 55 years(medium 29), including ten P190, three P210, one special BCR-ABL1 and nine hematological relapse, two FCM-MRD+, two BCR-ABL1+:one with multiple EMD, one only central nervous system leukemia(CNSL). After HSCT, twelve patients relapsed within 12 months(1.5-12 months), two patients relapsed in the 28th and 48th month. Twelve patients had received chemotherapy, TKI, donor lymphocyte infusion (DLI), murinized CD19-CART, radiotherapy before, but all failed;Two patients didn’t received any therapy.

Thirteen patients were detected AKDM:five T315I, one T315I and Y253H, one T315L, one Y317L, five no mutation(one T315I before HSCT). One patient didn’t detect AKDM because blast cells was not enough.

After first CART therapy, two patients had no effect and died, one patient gave up and died. Another 11(100%) patients all achieved CR and MRD negative(CRMRD-) with incomplete blood count recovery(CRiMRD-), and 10/11(90.91%)patients achieved molecular complete response (CRmi) and all of them hadn’t CNSL. ALL these patients received other therapies:three patients received second CART and one then received DLI, TKI was used in eleven patiets based on their AKDM results. To the present, eleven patients remained CRm:two patients stoped use TKI in February and July 2019, one patient received second HSCT in May 2019.

Cytokine release syndrome(CRS) occurred 9/14(64.29%)patients after the first CART:8 grade I, 1 grade III. Only one patient exhibited CAR T-cell-related encephalopathy syndrome (CRES) who had CNSL before CART, and no fetal graft-versus-host disease(GVHD)occurred.

Conclusions: CART therapy for Ph+ALL patients relapsed after HSCT is efficacy

and secure, once they achieved CR after CART therapy, sequencial TKI therapy may prolong the overall survival, leukemia free survival.

Disclosure: Nothing to declare.

Cellular Therapies other than CARs

¹CHRU de Nancy, Vandoeuvre les nancy, France, ²Université de Lorraine, UMR CNRS 7365, Vandoeuvre les Nancy, France, ³CHU de Bordeaux, Bordeaux, France, ⁴SFGM-TC, Lyon, France, ⁵CHRU de Strasbourg, Strasbourg, France, ⁶Hôpital Saint-Louis, Paris, France, ⁷EFS, Créteil, France, ⁸EFS, Saint Denis, France, ⁹Hôpital Robert Debré, Paris, France

Background: Viral infections are major complications of Hematopoietic Stem Cell Transplantation (HSCT). As efficacy of anti-viral drugs is limited in absence of immune reconstitution and often associated with severe side effects, infusion of Virus-Specific T cells (VSTs) becomes a promising alternative treatment for viral infections and diseases after HSCT. We previously performed a successful phase I/II clinical trial and secondarily obtained an ATMP under hospital exemption authorization from the French regulatory agency for the preparation of VSTs (especially ADV-STs) for all the clinical centers in need. A national group was created under the aegis of the Francophone Society of Bone Marrow transplantation and Cell Therapy (SFGM-TC) to analyze, validate and follow the different requests. We present here the results that have been collected until 2016.

Methods: We previously demonstrated the feasibility of isolating ADV-STs from donors using the IFNg-capture system from Miltenyi biotec followed by immunomagnetic selection on the CliniMACS device (Aissi-Rothé et al, 2010; Qian et al, 2017). Since we obtained the ATMP authorization, we have treated patients with an infusion of polyclonal ADV-STs (n=8) or CMV-STs (n=4) or EBV-STs (n=2) generated by a 6-hour ex vivo stimulation with an appropriate peptide pool (PepT-ADV5 Hexon, PepT-CMV pp65, PepT EBV Select, respectively, Miltenyi Biotec) of leukapheresis collected from their original stem cell donor or more often from third party haploidentical donors, followed by isolation of IFNg producing cells.

Results: We report more than 40 requests to the group, 75% of them in 2019, from different French and Belgium centers followed by 8 refusals, the generation of 14 VST preparations and the infusion of patients (4 months-65 years) with viral infection disease. They received a mean of 0.96 10⁴ CD3-IFNg+ cells/kg (range: 0,042 to 1.436 10⁴). In vivo expansion of transferred VSTs was observed from day 15 to 60 following adoptive transfer infusion associated with viral load decrease or clearance in more than half of the patients. During the 3 month-follow-up, 4 patients experienced failure of the treatment with a persistent increase of viral load. Neither de novo GVHD, nor side effects were observed. Reactivation of grade I aGVHD occurred in 2 patients in the month following infusion and in 3 patients after D45 (grade II and IV). Unfortunately, eight patients died, 4 related to persistent viral infection or disease. However, none of the responders experienced a viral-associated mortality.

Conclusions: Adoptive transfer of VSTs is a feasible and well-tolerated therapeutic option, representing a fast and efficient procedure to achieve reconstitution of antiviral T-cell and decrease or clearance of viral load. However, today this is a last chance therapy and viral load is often over 6.5 log (4 patients) when infusion is performed, not giving VST time to expand and be efficient. The French organization, under the aegis of SFGM-TC, is very secure and reactive and contributes to encourage clinical centers to initiate their request earlier.

Disclosure: Danièle Bensoussan, start up StemInov, CSO

¹Università San Raffaele, Milan, Italy, ²IRCSS San Raffaele Hospital, Milan, Italy

Background: A notable percentage of blood cancer patients who undergo Allogeneic Hematopoietic Stem Cell Transplantation (alloHSCT) still suffers a dismal prognosis; this therapeutic gap could be filled by Adoptive T cell therapy, but its exploitation is still limited by the incomplete knowledge of tumor-specific T cells dynamics in vivo and by the difficulty to isolate such T cell specificities for therapeutic purposes.

Methods: To visualise and purify tumor-specific T cells ex vivo, we screened circulating cells at 30,60,90,120,180 and 365 days after alloHSCT in N=35 patients affected by blood malignancies with a 18-colour Flow Cytometry panel including fluorescent MHC-I complexes loaded with Tumor-Associated Antigen (TAA) peptides or with a viral peptide. Together, we followed T-Cell Receptor (TCR) clonal dynamics by cell sorting and sequencing.

Results: TAA-Specific T cells were found circulating in the patients’ peripheral blood, as soon as 30 days after alloHSCT. By exploiting high-dimensionality un-biased analytical tools we dissected their phenotype, showing that they express multiple inhibitory receptors at higher levels if compared with either the total CD8 T cell population or viral-specific T cells, independently from major clinical variables (disease status at transplant, disease type, GvHD incidence). The inhibitory signature was the most pronounced 4 months after alloHSCT, and was followed by a substantial contraction of the pool of TAA-specific memory T cells.

We also took advantage of cell sorting to isolate and expand TAA-specific T cells. We established a rapid, highly specific protocol that isolated 24 tumor-specific T cell colonies from n=13/20 screened patients, each one enriched for a single TCR clonotype identified by RNA sequencing. When challenged with peptide-pulsed targets, such ex vivo clones were poorly responsive but when the TCR sequences were cloned into lentiviral vectors and transferred in T cells after Crispr/Cas9 disruption of the endogenous TCR (TCR-edited lymphocytes), cells proved highly efficient and specific in lysing matched pulsed targets (fig.1A). This observation, linked with the previous phenotypic analysis, suggests that TAA-specific T cells are circulating in vivo but are exhausted. We thus tried to broaden the search of Tumor-reactive T cell clones by exploiting the exhaustion signature to purify a T cell subset enriched with anti-tumour reactivities. We sorted T cells from 3 patients affected by Acute Myeloid Leukemia (AML) on the basis of the inhibitory receptors (IR) expression and stimulated both IR+ and IR- cells with matched Leukemic Dendritic Cells (LDC). Serial LDC stimulations promoted the expansion of dominant clones over time in the IR+ but not in the IR- fraction and IR+ T cells proved superior in killing autologous AML blasts in vitro. Again, dominant TCRs were identified in IR+ cultures from the first patient, and TCR-edited lymphocytes efficiently and selectively recognized autologous blasts (fig.1B).

Conclusions: Our findings shed some light on the in vivo dynamics of tumor-specific T cells and introduce two models for the isolation of tumor-specific TCRs, one requiring the knowledge of the target peptide, the other exploiting the IR signature to discover novel tumor specificities.

Disclosure:

Chiara Bonini recieves Resarch funds from Intellia Therapeutics and Immudex, and she´s consultant for Intella Therapeutics, Novartis and Molmed.

The other authors declare. no relevant conflict of interest

¹George Papanikolaou Hospital, Thessaloniki, Greece, ²University General Hospital of Patras, Patras, Greece, ³Aristotle University of Thessaloniki, Thessaloniki, Greece, ⁴Altius Institute for Biomedical Sciences, Seattle, WA, United States, ⁵Centre for Research and Technology Hellas (CERTH), Thessaloniki, Greece

Background: Adoptive immunotherapy (AI) with pathogen-specific T cells (pSTs) is a promising alternative to pharmacotherapy for the treatment of opportunistic infections after allogeneic hematopoietic stem cell (allo-HSCT) or solid organ transplantation. However, clinical implementation of AI is limited to patients receiving either low dose or no steroids, a prerequisite for optimal T-cell function, practically excluding the most susceptible to infections patients from the benefits of AI. Aims. We evaluated the impact of dexamethasone (DEX) on primary T cells and developed a CRISPR/Cas9 system to genetically disrupt the glucocorticoid receptor (GR) in lymphocytes and confer resistance to steroids, in order to ultimately develop steroid-resistant pSTs.

Methods: The impact of DEX on T cell proliferation, phenotype and apoptosis was evaluated in human OKT3 blasts generated by stimulating peripheral blood mononuclear cells through CD3 and CD80 ligation. To inactivate the GR gene, 10 guide RNAs (gRNAs) were prepared to target different genomic sequences corresponding to various domains of the GR (a transcription start site, and exons 2, 3, 4 and 5) and delivered separately into the T2 lymphoblastic cell line using lentiviral vectors. Cells transduced with an “empty” viral vector expressing Cas9 but no gRNA were used as negative control. The resistance of T2 cell line to glucocorticoids was assessed as cell viability by trypan blue exclusion. The on-target inactivation of the GR in T2 cell line was measured by western blot and T7 assay.

Results: A 3-day exposure of OKT3 blasts to DEX negatively impaired the proliferation of stimulated primary T cells and induced early apoptosis over the “no DEX” condition (p=0.001, p=0.01 respectively). These effects correlated with a DEX-induced upregulation of T regulatory cells (p=0.0002). DEX also upregulated PD-1 and CTLA-4, the major coinhibitory molecules in antigen-specific immune responses, over the “no DEX” condition (p< 0.05). Then, in order to render cells steroid-resistant, T2 cells were transduced with lentiviral vectors encoding Cas9 and 10 different gRNAs targeting GR and subsequently incubated in the presence or absence of DEX. T2 cells edited with 7/10 single gRNAs, presented normal proliferation on DEX treatment as contrasted to their untreated counterparts and the empty vector-transduced cells, suggesting functional DEX-resistance. The on-target GR inactivation in T2 cells was confirmed by both western blot and T7 assay. Among tested functional gRNAs, the optimal gRNA was selected for further studies, on the basis of high GR disruption efficiency and low off-target activity.

Conclusions: Overall, we provide a series of gRNAs to CRISPR/Cas9-disrupt the GR and ultimately generate steroid-resistant pSTs in order to offer the benefits of AI to the most vulnerable to infections patients, as those with graft-versus-host-disease receiving high-dose steroids post allo-HSCT.

Disclosure: Funding for this project was provided in part by an EHA Research Grant award granted by the European Hematology Association and in part by the State Scholarships Foundation (I.K.Y.).

¹Princess Margaret Cancer Centre, Toronto, Canada, ²University of Toronto, Toronto, Canada

Background: Allogeneic hematopoietic cell transplantation (HCT) is potentially curative for a variety of benign and malignant hematological disease, however may be complicated by disease relapse or graft loss/poor graft function. Both second allogeneic HCT and donor lymphocyte infusions are utilized in the management of both complications. The purpose of the present study is to compare outcomes following both interventions in a single center cohort of patients transplanted over the last five years.

Methods: We retrospectively investigated 65 patients in total, 34 (52%) underwent second allogeneic HCT and 31 (48%) received donor lymphocyte infusions (DLI), from June 2011 to November 2018.

Results: Median patient age at the time of the post-transplant intervention was 51 years (range 19-72). Second HCT was performed for disease relapse in 11 patients (5 of which were transplanted for AML) and for graft failure (GF) in 23 patients (primary in 6 and secondary in 17 patients). Donors for second HCT were related (n=10), unrelated (n=18) and haploidentical (n=6), the same donor was used in 20 (59%) patients. At second HCT, the HCT-CI was 0-2 for 22 patients (65%) and ≥3 for 12 patients (35%). Concerning DLI patients, this was performed for relapse for 17 patients (8 of which were transplanted for AML) and for secondary GF or chimerism loss in 14 patients. Donors for DLI were related for 13 patients, unrelated for 16 patients and haploidentical for 2 patients. KPS at first DLI was 90-100% for 20 patients (65%) and 70-80% for 11 patients (35%). Median number of DLI administered was 2 (range 1-11).

[Figure 1: Overall survival with second transplant vs donor lymphocyte infusion for relapsed patients]

Median follow-up of survivors following intervention was 18 months (range 3-66 months). Univariate analysis demonstrated 2-year overall survival (OS) of 50% (95%CI 37-62%) for the entire cohort, while 2 year OS was identical between all second transplant patients and DLI patients (50% for both groups, p=0.9%). For second HCT patients, 2-year OS was 82% (95%CI 45-95%) and 35% (95%CI 17-54%) for relapse as an indication versus GF respectively (p=0.01). For the DLI patients, 2-year OS was 44% (95%CI 20-66%) and 56% (95%CI 27-78%) for relapse as an indication versus GF/loss of chimerism respectively (p=0.64). For disease relapse as an indication, second HCT was significantly superior to DLI (p=0.03, Figure 1). Multivariable analysis for second HCT patients demonstrated age (HR 1.04, 95%CI 1.00-1.07, p= 0.03) and donor type (HR 0.17 for related donor, 95%CI 0.04-0.75, p=0.02) to independently predict OS. For DLI, multivariable analysis demonstrates KPS at the time of the first dose of DLI as the predominant predictor of survival (HR 0.89, 95%CI 0.82-0.96, p=0.002).

Conclusions: Second allogeneic HCT demonstrates superior survival when performed for disease relapse post-transplant compared to DLI. In contrast, second HCT for graft failure results in poor long-term survival. Second allogeneic HCT should be preferred as a reasonable treatment option for patients that relapse post-transplant and achieve pre-second HCT remission.

Disclosure: Nothing to declare.

¹Miltenyi Biotec B.V. & Co. KG, Bergisch Gladbach, Germany, ²National and Kapodistrian University of Athens, Athens, Greece

Background: Major complications of allogeneic stem cell transplantation are GvHD and infections. Ex-vivo T cell depletion (TCD) can effectively prevent GvHD, however it may prolong immune reconstitution and increase the risk of infections. Depletion of TCRab⁺ T cells combined with the transfer of CD45RA^- donor memory T cells may ameliorate the infection risk and simultaneously decrease the risk of GvHD. Here, we report the development of a single, automated manufacturing process on the CliniMACS Prodigy^® to generate personalized grafts providing a TCRab-depleted stem cell product and a memory T cell product.

Methods: Currently, the combined depletion of TCRab⁺/CD19⁺ cells and the depletion of CD45RA⁺ cells exist as two separate applications on the CliniMACS Prodigy. The novel integrated CliniMACS Prodigy LP-TCRab-19-45RA depletion process merges these two strategies in one application performed in one tubing set, namely CliniMACS Prodigy TS 320. Depending on the desired cell composition of the graft, the user can choose to perform either:

· sequential depletion of CD45RA⁺ and TCRab⁺ cells with or without simultaneous depletion of CD19⁺ cells,

· a depletion of TCRab⁺ cells with or without simultaneous CD19⁺ cells or

· a CD45RA⁺ cell depletion only.

All TCRab depletion cases (with or without simultaneous depletion of CD19⁺ cells) can be performed in normal or large scale, depending on the number of total WBC, TCRab⁺ and CD19⁺ cells. The memory T cell product and the stem cell product are collected in separate bags and can be combined to a single cell product, according to each patient’s need (personalized graft).

The new application software effectively depletes 2.4x10⁹ CD45RA⁺ cells from up to 6x10⁹ total WBC, and 48x10⁹ total TCRab⁺ cells plus 15x10⁹ total CD19⁺ cells from up to 120x10⁹ total WBC.

Results: In-house evaluation runs (total n = 41, 10 mobilized and 31 non-mobilized apheresis products) resulted in comparable values for depletion, yield, recovery, and WBC viability of the target products regardless of the application case performed. The mean log depletion achieved for the TCRab±CD19-depleted products (n = 41) was 4.5 (range 3.5-5.2) for TCRab⁺/CD45RA⁺ cells and 3.4 (range 2.6-4.3) for CD19⁺ cells with a stem cell viability over 90% and mean yield of 81%. In the CD45RA-depleted products (n=31) a mean log depletion of 5.4 (range 3.8-6.4) for TCRab⁺/CD45RA⁺ cells was obtained.

The duration of CD45RA depletion takes between 1.5-1.7 hours, while the duration of TCRab±CD19 depletion ranges between 5.1-8.3 hours. Finally, the combined TCRab±CD19/45RA depletion needs 6.7-10.3 hours to complete, depending on total cell numbers. Importantly, input of a defined process end time is possible.

Effective quality control panels and express modes for MACSQuant^® Flow Cytometers enable easy and accurate monitoring of the entire cell manufacturing process.

Conclusions: In summary, the novel automated CliniMACS Prodigy LP-TCRαβ-19-45RA depletion process is capable to deplete CD45RA⁺, TCRab⁺ and CD19⁺ cells efficiently from apheresis products with a mean yield of 81% for CD34⁺ cells. The performance verification and submission to an European notified body for CE marking as medical device application are the important next steps.

Clinical Trial Registry: n/a

Disclosure: n/a

¹Banc de Sang i Teixits, Barcelona, Spain, ²Hospital Vall d´Hebron, Barcelona, Spain, ³Santa Creu i Sant Pau Hospital, Barcelona, Spain, ⁴Hospital Sant Joan de Déu, Esplugues de Llobregat, Barcelona, Spain, ⁵ICO - Hospital Duran i Reynals, Barcelona, Spain

Background: Acute graft-versus-host-disease (aGVHD) is one of the main complications derived from an allogeneic hematopoietic progenitor cell transplant (HPCT). First line therapy is based on the use of steroids but many patients are refractory. Due to the immunomodulatory characteristics of multipotent mesenchymal stromal cells (MSC) this cell type have been used with success in the treatment of refractory aGVHD. Wharton Jelly’s (WJ) is a new source of MSC with advantages for large-scale production and standardization. The aim of this study is to evaluate the ability of WJ MSC’s to improve refractory aGVHD compared to MSC’s obtained from Bone Marrow (BM).

Methods: Retrospective study of patients with refractory aGVHD treated with MSC produced at Banc de Sang I Teixits between (2017-2019). All patients received at least two doses of MSC (1E6 MSC/kg of patient body weight per dose). To obtain and process the cells, an approved IND was followed in our production facilities using BM-MSC’s (PEI 13-081) or WJ-MSC’s (PEI 16-017). Patients were treated in 4 hospitals of Barcelona area, after receiving corticosteroids and second or further lines of alternative drugs. Upon request by transplant center, MSC samples were released for a therapy scheduled for infusion on days 1, 4, 11 and 18 using a compassionate schema.

Results: Eighteen patients (12 pediatric and 6 adults) have been treated during this period. Table 1 shows diagnosis, graft source, GVHD grade and organ involvement and MSC source. The first MSC infusion was performed on median 5 months after the onset of the GVHD (range 0.6 to 46). There were no adverse reactions related to the MSC infusions. Two patients died before day 7 due to sepsis and viral infection not related to the procedure. They received only 2 doses of therapy and were not included in the survival analysis. Over 16 patients, five patients died due to GVHD progression, relapse or infection. Remarkably, ten patients (63%) have responded to treatment, and five (31%) achieved complete response. Responders achieved high overall survival. The median response time was 14 days after the first MSC infusion (range, 7-28 days). Evaluating performance status (Karnofsky/Lansky scale) median improvement was in day 21 (range, 7-49 days). One responder died later on time, due to sepsis after achieving CR. According to the source of MSC, 7 of 12 evaluable patients that were treated with WJ-MSC responded to treatment (58%), comparable to 3 of 4 from BM-MSC (75%).

Conclusions:

MSC treatment resulted in a safe procedure with a response rate of 63% of heavily pretreated patients. WJ-MSC showed similar results than BM-MSC. These results show the feasibility and support the proposal of a prospective trial in order to demonstrate efficacy in this setting.

[Table 1]

Disclosure: Nothing to declare.

¹George Papanikolaou Hospital, Thessaloniki, Greece, ²Aristotle University of Thessaloniki, Thessaloniki, Greece, ³King Fahad Specialist Hospital Dammam, Dammam, Saudi Arabia

Background: Leukemic relapse and opportunistic viral infections represent the major causes of morbidity and mortality post allogeneic hematopoietic cell transplantation (allo-HCT). T-cell immunotherapy with chimeric antigen receptor T-cells (CAR-Ts) is currently the spearhead of research in refractory hematological malignancies, however, CAR-Ts for myeloid leukemias lag well behind CAR-Ts for B-cell lymphoid malignancies, mainly due to the lack of an appropriate, targetable antigen. On the other hand, while immunotherapy with non-genetically engineered virus-specific T cells has been shown to successfully control viral infections post-allo-HCT, single-epitope leukemia-specific T-cells (Leuk-STs) targeting the less immunogenic leukemia-associated antigens (LAAs) have met limited clinical success. Aim. By adapting our previously developed protocol of generating multivalent Leuk-STs, targeting multiple epitopes of various leukemic antigens by stimulation with overlapping peptides spanning the whole proteins, we here aimed to generate a non-engineered, “all-in-one”, T-cell product from Non-Transplantable Umbilical Cord Blood Units (NT-UCBUs), called LEukemia-VIrus-specific T-cells (LEVIS), which simultaneously targets four viruses and two common LAAs.

Methods: Matured CD34+-derived dendritic cells from NT-UCBUs were stimulated with both leukemic [Wilms tumor protein (WT1) and Preferentially Expressed Antigen in Melanoma (PRAME)] and viral [EBNA1, LMP2 and BZLF1 (EBV); IE1 and pp65 (CMV); Hexon and Penton (AdV) and Large-T and VP1 (BKV)] pepmixes and used to “educate” autologous, naive T-cells.

Results: By reclaiming disqualified for allo-HCT NT-UCBUs and using our approach, we have been consistently obtaining clinical doses of LEVIS (CD3+ cells: 1.01±0.2x10⁸). The resultant T-cell products are polyclonal, containing both CD4+ and CD8+ T-cell subsets (39±2% and 50±2%, respectively), expressing effector memory (CD45RA-/CD62L-: 47.36±5%) and effector memory RA markers (CD45RA+/CD62L-: 48.50±4%), while containing insignificant amount of naïve and regulatory (CD4⁺/CD25^high) T cells. LEVIS demonstrated high specificity against all targeted antigens [spot-forming units (SFC)/2x10⁵ cells: CMV: 311±149, EBV: 319±111, BKV: 245±122, AdV: 432±32, Leuk: 553±257], similar to that conferred by Leuk-STs alone, suggesting successful “training” of naïve T cells and lack of antigen competition by the addition of immunodominant viral antigens. Importantly, LEVIS demonstrated low expression levels of Programmed cell Death protein-1 (PD-1) and barely detectable Cytotoxic T-Lymphocyte Associated Protein-4+ (CTLA-4), which remained stable throughout the culture, suggesting that persistent antigen exposure did not impair their Th-1-polarized function in vitro, an effect that could be translated into anti-leukemic and antiviral response after infusion.

Conclusions: Overall, by “recycling” NT-UCBUs, we provide the potential for future banking of LEVIS, to serve as third-party, “off-the-shelf”, multipotent T-cell products, thus further optimizing adoptive immunotherapy and improving the outcome of allo-HCT.

Disclosure: Nothing to declare.

Technische Universität Dresden, Dresden, Germany

Background: For decades, granulocyte transfusions (GTX) have been performed to treat neutropenic haematological patients with infectious complications. Nevertheless, the clinical efficacy of this cellular therapy is remaining controversial.

Methods: We performed a risk factor analysis in a large cohort of patients who received GTX between 2004 and 2014 at the University Hospital Dresden. Demographical data, diagnosis and outcome of the patients were registered. Among other parameters, type and state of the infection, dosage of the transfused granulocyte concentrates, and adverse effects had been recorded during each GTX cycle. GTX during an active infection were considered as “therapeutically” and GTX in patients who previously had survived life-threatening infections were considered as “prophylactically”. We evaluated overall survival and day-30-mortality from infection according to several risk factors. Treatment-cycle- or product-related variables were modeled as time-dependent variables and analyzed with Cox regression with time-dependent covariate. Cumulative incidences of infection related deaths were estimated according to the methodology of Gray. Competing risk was death from other causes than infection. The cause specific hazard for death due to infection was estimated with Cox regression.

Results: A total of 187 patients received 886 transfusions within 232 treatment cycles. The mean dose was 8.05 ∙ 10¹⁰ neutrophil cells (SD =2.5) per transfusion. In 194 of 232 cycles (84 %) granulocytes were transfused therapeutically, in 37 cycles (16 %) prophylactically.

Patient-related factors had impact on clinical outcome. State of the infection appeared to be the most important factor: Patients with septicemia had significantly lower treatment success than patients with localized infections with a significantly lower Overall survival (HR 2.4; CI: 1.68 - 3.52; p < .001) and a 4.8-fold higher cause specific hazard for infection-related death within 30 days after the first GTX (CI: 2.48 - 9.32; p < .001). Analysis of surrogate parameters for the severity of infections supported these findings (e.g. patients in ICU, patients requiring ventilation support, bacterial versus mycotic infections or a combination of both).

Among transfusion-related factors, early administration of GTX was favorable for therapeutic success. Patients with prophylactic GTX had a significantly lower 30-day-infection-mortality than patients with therapeutic GTX (HR 0.14; CI: 0.02 - 0.94; p = .044) and a slightly better overall survival (HR 0.71; CI: 0.38 - 1.27; p = .238). Patients who received ≥ 4∙10¹⁰ granulocytes per transfusion had a significant lower 30-days-infection-related mortality (HR 0.76; CI: 0.63 - 0.92; p = .005). Transfusion reactions were seen in 60 out of 886 (7 %) transfusions. Our analysis revealed no difference in the frequency of side effects with respect to the amount of granulocytes per transfusion (HR 0.95; CI: 0.67 - 1.34; p = .756).

Conclusions: Our data indicate that patients receiving GTX at an early stage of their infection seem to particularly benefit from this treatment. High dose GTX seem to be advantageous, In our cohort, GTX proved to be a safe approach without any severe side effects.

Nevertheless, these retrospective data are limited and should be validated in further prospective controlled studies.

Disclosure: Nothing to declare.

CHU Amiens Picardie, Amiens Cedex, France

Background: Freezing and storage of hematopoietic stem cells (HSC) graft are keys steps of therapeutic intensification process by autograft. No maximum storage period is defined in literature and less data are available concerning the quality of graft cryoconserved for a long duration. Now a day, only the notion that storage duration more than 15 years may be potentially harmful was advanced by 2014 SFGM-TC guidelines. (Calmels and al, Pathologie biologie 2014; 62: 221-225)

Methods: Fifty seven autologous grafts with long term storage (more than 5 years) were thawing in our study and were:

- evaluated by a quality control using Stem-Kit (Beckman Coulter, France) by flow cytometer including: viability/total nucleated cells count (TNC), viability/number of CD34+ cells, hematopoietic reconstitution evaluation (CFU-GM)

- compared with 60 short-term storage autologous grafts (less than 2 years) thawing routinely in laboratory.

Results: By comparison with routinely thawing graft quality criteria, we observed that CD34+ yield (p< 0.0001), TNC yield (p = 0.037) and number of CFU-GM/kg (p< 0.0001) were negatively impacted, based on lengthening of storage period. Moreover, we highlighted a significatively decreased of clonogenicity linked with increase graft storage duration (p=0.02).

Conclusions: Autologous graft long-term cryopreservation has a clear impact on product quality, in view of decreased CD34+ cells as well as CSH functionality in vitro. No national consensus defining cryopreservation modality and grafts storage, capable of influencing positively or negatively grafts quality, notably during long term conservation.

Disclosure: Nothing to declare.

¹UMC-Utrecht, Utrecht, Netherlands, ²MSKCC, New York, NY, United States, ³AVROBIO Inc, Cambridge, MA, United States, ⁴Princess Máxima Center for Pediatric Oncology, Utrecht, Netherlands

Background: Adoptive T cell therapy utilizing autologous T cells has shown promising results for cancer treatment. However, the limited numbers of tumor associated antigen (TAA)-specific T cells and the functional aberrancies due to disease progression or treatment remain factors that may significantly limit the success of the therapy. The use of allogeneic T cells as an off-the-shelf therapy overcomes these issues, but requires gene-modification to induce a robust and specific anti-tumor effect. Umbilical cord blood (CB) might be particularly suited for this purpose; CB T cells are readily available in cord blood banks, show low toxicity, high proliferation rates and increased anti-leukemic effect upon transfer. Moreover, CB T cells can be used as combinational therapy in the hematopoietic cell transplantation setting to prevent minimal residual disease, relapses, and completely eradicate all tumor cells. However, combining anti-tumor gene modification and preserving advantageous immunological traits of CB T cells represents a major challenge for the harmonized production of T cell therapy products.

Methods: CB CD8⁺ T cells were isolated from fresh CB donors, subsequently expanded and activated. CB CD8⁺ T cells were transduced with lentiviral vectors (LV) expressing GFP and WT1-TCR, in order to compare methods, culture media, promoter strength and use of transduction enhancers. Analysis of immune-phenotype was performed in CB CD8⁺ T cells and PB CD8⁺ cells after isolation, expansion and transduction.

Results: In this manuscript we describe an efficient protocol to expand and transduce CB CD8⁺ T cells using LV, achieving an efficiency up to 83% of transduced cells. The protocol was established by optimizing the timing of LV treatment, selection of culture media, and application of different promoters. We confirmed LentiBOOST as a non-toxic transduction enhancer, however its use decreased the proliferation capacity of the T cells. Finally, we show that CB CD8⁺ T cells were more amenable to LV transduction than PB CD8⁺ T cells, and that the immune phenotype of the two cell sources were remarkably different with respect to the expression of inhibitory receptors and maturation markers.

Conclusions: We show an efficient method of gene modification of CB CD8⁺ T cells using LV, which is especially useful for off-the-shelf adoptive cell therapy products for cancer treatment, especially in post hematopoietic cell transplantation setting.

Disclosure: Nothing to declare.

Hospital Universitario La Princesa, Madrid, Spain

Background: Donor Lymphocyte Infusion (DLI) is often used to treat relapsed haematological malignancies after allogeneic stem cell transplantation. DLI is an immune-mediated therapy, mainly driven by the antitumor effect of donor T cells which can, in part, augment the graft-versus-tumor effect. However it can sometimes induce fatal adverse events such as severe graft-versus-host-disease (GVHD) and infectious complications.

Methods: We retrospectively analyzed 72 patients who received DLI for treatment of relapsed haematological malignancies, who had been allotransplantated in our centre between 1994 and 2018. Median age of 43 years old (range 16-70) at the time of DLI. Underlying diseases treated with DLI included chronic myeloid leukemia (CML) (n=20), acute myeloid leukemia (AML) (n=20), acute lymphocytic leukemia (ALL) (n=11), Hodgkin lymphoma (HL) (n=8), non Hodgkin lymphoma (NHL) (n=7), myelodysplastic syndrome (MDS) (n=5) and multiple myeloma (MM) (n=1). Fifty-nine patients received HLA-matched sibling donor, 2 haploidentical related donor and 11 matched unrelated donor transplant. Conditioning regimen was mieloablative in fifty-three patients, and reduced intensity conditioning in nineteen patients. All patients received DLI as treatment for relapsed disease after allogenic transplantation. In the present study we analyse response rate, graft-versus-host-disease (GVHD), progression free survival (PFS) and overall survival (OS).

Results: Our patients received a median of 3 infusions (range 1-5). The median number of infused CD3+ cells was 0.5x10⁸/kg (range 0.1x10⁸/kg to 2.84x10⁸/kg). Sixty-eight percent of patients received dose-escalation DLI. Patients with low disease burden only received DLI. Thirty-nine percent received DLI-associated therapy (chemotherapy, radiotherapy, tyrosine-kinase inhibitors).

From the sixty-three patients eligible for evaluation, 35 (56%) got clinical benefit (CML n=14, ALL n=6, AML n=6, HL n=5, MDS n=2 NHL n=2). Progression free survival was higher in CML, with a median of 132 months, followed by NHL (84 months). Acute graft-versus-host-disease developed in 15% of the patients (5 patients grades I-II, the other 5 grades III-IV). Two patients died from acute hepatic GVHD. Chronic GVHD developed in 22% (6 cases limited, 9 extend). One patient died from chronic pulmonary GVHD.

With a median follow up of 16 years, median progression-free survival was 120 months [IC 95% 84.51-155.49] for the whole series. There are substantial survival differences according to underlying diseases, with a better survival rates for CML and LH.

Conclusions: Inmunotherapy with DLI is an attractive strategy for relapsed patients after allogeneic transplantation. In our experience, patients with CML have more clinical benefit, with a response rate of 70%, similar to published. DLI response in other pathologies is lower, although it can be useful in association with other therapies. However, further studies are needed to develop strategies to reduce toxicity and enhance anti-tumor activity.

Disclosure: Nothing to declare.

¹University Medical Center Regensburg, Regensburg, Germany, ²Hannover Medical School, Hannover, Germany, ³Hannover Medical School, Hannover, Germany, ⁴University of Ulm, Ulm, Germany, ⁵German Red Cross Blood Service, Baden-Wuerttemberg-Hessen, Ulm, Germany, ⁶German Cancer Research Center (DKFZ), Heidelberg, Germany, ⁷German Center for Infection Research (DZIF), Braunschweig, Germany

Background: Chronic active Epstein-Barr virus infection (CAEBV) is one of the Epstein-Barr virus (EBV)-positive lymphoproliferative diseases. It is a rare and often fatal complication of EBV infection. In CAEBV, EBV-infected B-, T- or NK-cells clonally proliferate and infiltrate multiple organs, leading to their failure. At present, allogeneic hematopoietic stem cell transplantation (alloHSCT) is the only curative therapy. Other treatments such as high-dose systemic corticosteroids or ganciclovir combined with either histone deacetylase inhibitors or proteasome inhibitors (e. g. bortezomib) may temporarily reduce systemic toxicity and allow the patient time to receive a transplant.

Methods: We report a case of T-cell-type CAEBV in a 27-year-old female caucasian patient with severe skin, neurological, hepatic and pulmonary involvement.

Results: After several therapeutic approaches including high-dose systemic steroids, ganciclovir combined with bortezomib and rituximab had failed with EBV encephalitis requiring mechanical ventilation, third-party EBV-specific T-cells were administered and clinical symptoms resolved, while EBV viremia persisted. Subsequently, alloHSCT was performed from an HLA-matched unrelated donor after conditioning with antithymocyte globulin (ATG), fludarabine and treosulfan followed by an alpha-beta T-cell depleted and EBV-specifc T-cell enriched peripheral stem cell graft and GvHD prophylaxis with everolimus. Intriguingly, the viremia cleared after administration of ATG in alloHSCT setting. When the virus reactivated again in persisting host T-cells everolimus was tapered and viremia could again be controlled by transfusion of donor derived EBV-specific T-cells. Until now, no underlying immunodeficiency was found in the patient while complete host genome DNA and EBV genome sequencing is pending.

Conclusions: Treatment with EBV-specific T-cells from a third party donor followed by alloHSCT from an EBV seropositive donor is an effective therapeutic approach in CAEBV. As EBV-viremia was cleared after the administration of ATG in the alloHSCT setting for the first time in the patient, ATG might be further analysed as a potential treatment option in T-cell-type CAEBV due to its depletive activity on T-cells.

Disclosure: Nothing to declare.

Chronic leukaemia and other myeloproliferative disorders

University Hospital Eppendorf, Hamburg, Germany

Background: Despite advances in transplantation procedures and significant prolongation in survival, relapse following allogeneic hematopoietic stem cell transplantation (SCT) for myelofibrosis (MF) remains a significant issue. Most relapse occurs during the early period of allogeneic SCT. We aimed to analyze the clinical characteristics of the patients with late relapse following allogeneic SCT.

Methods: In this cross-sectional study we retrospectively evaluated the files of 259 patients with myelofibrosis transplanted between 1994 and 2015 for late relapses. Late relapse was defined as the relapses later than first five years of stem cell transplantation (SCT). Study patients were grouped according to their relapse status under follow-up after five years. Group A consisted of patients with a late relapse. Patients under long term follow-up after five years with no relapse consisted Group B. Clinical and laboratory parameters of late relapse were investigated.

Results: A total of 94 patients (M/F=55/39, 58.5 vs. 41.4%, respectively) out of 259 MF transplant patients were identified with a median follow-up of 9.15 years (range, 5.12-19.61). Median age at transplantation of the whole study population was 56 (range;29-75). Sixty two patients (66%) had primary MF (PMF), 18 (19.1%) had post polycythemia vera (PV) and 14 (%14.9) had post essential thrombocythemia (ET) myelofibrosis. Thirteen patients (M/F=7/6) experienced (12%) late molecular (n=6) or hematological (n=6) relapses at a median of 7.1 years (range, 5.02-10.20). Eighty- one patients (M/F=48/33) with a median follow-up of 8.76 years (5.02-19.61) did not experienced relapse. Median age at transplant was similar in both groups (Group A vs Group B: 55 (36-73) vs. 57 (29-75)). Although, numerically smaller, median time from diagnosis to transplantation, 20 months (3-100) in Group A and 13 months (1-353) in Group B, had no effect on relapses. Other clinical and laboratory parameters analyzed were not associated with a significantly higher risk of late relapse. Relapse patients received either DLI (n=9) and/or second transplantation (n=4). Of those 61.5 % achieved again full donor cell chimerism and/or molecular remission. After a median follow up of 105 months (range,4-236) of the relapsed patients the 2 years PFS and overall survival is 92.3% and 84.6%, respectively.

Conclusions: In this large MF group we observed late molecular or hematological relapses. DLI and second SCT are effective to induce remission. Early detection of minimal residual disease (MRD) and therapy adjustment resulted in full chimerism and negative MRD status. Our results implicate the importance of close monitoring of MF patients even after 5 years post allograft.

Disclosure: Nothing to declare.

¹Università Sapienza, Rome, Italy, ²Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy, ³Università Tor Vergata, Rome, Italy

Background: Myelofibrosis (MF) is a rare BCR-ABL negative myeloproliferative neoplasm, which can only be cured by Hematopoietic Stem Cell Transplantation (HSCT). Because of transplant related mortality (TRM) and morbidity, HSCT is reserved only to patients aged < 70 years with intermediate-2 or high risk MF, according to IPSS or DIPSS, or intermediate-1 with biological high-risk characteristics. Recently, Myelofibrosis Transplant Scoring System (MTSS) has been proposed in order to estimate the transplant risk. The aim of this analysis was to evaluate the outcomes of patients transplanted for MF in three University Transplant Centres in Rome and to verify the accuracy of MTSS in this population.

Methods: We retrospectively analysed 83 MF patients transplanted in Rome at Policlinico Umberto I (25 pts), Policlinico Tor Vergata (23 pts) and Policlinico Agostino Gemelli (35 pts), between 1986 and 2019 (75% of HSCT performed after 2012). Overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method. The log-rank test was used to compare risk factors categories. Cumulative incidence (CI) was used to calculate TRM, Relapse Risk (RR), graft failure (GF) and GVHD. A modified MTSS not including ASXL1 mutation was used (ASXL1 mutation data available for only 2 patients).

Results: Median age was 54 years (range 21 - 72). 44%, 28% and 28% of patients received transplant from HLA-identical related, unrelated and haploidentical donors, respectively. Peripheral hematopoietic stem cells were used in 59% of patients. RIC regimens (mainly Thiotepa, Busulphan and Fludarabine-based) were employed in 70%. Forty patients had been previously treated with Ruxolitinib: 27 patients responded or showed disease stability; 13 patients progressed during treatment. Modified MTSS was evaluated in 47 patients, for whom driver mutation data was available. The risk was low in 12 (25%), intermediate in 21 (45%) and high in 14 (30%) patients. Five-year OS was 60%. Features associated to a better OS were: Karnofsky ≥90% (p=0.04), spleen< 22 cm (p=0.04) and cGVHD (p=0.013). A trend to a worse OS was observed in patients who had progressed while in treatment with Ruxolitinib. At 5 years, DFS and RR were 56% and 22%, respectively. CMV and EBV reactivations were associated to an increased RR. TRM was 12% at 100 days, 20% at 1 year and 28% at 5 years. CI of GF at 100 days was 6.5%, with a higher risk trend for HSCT performed before 2012 and donor/recipient sex mismatch (F/M). Acute GVHD CI was 38% (III-IV grade 11% of patients). Two-year CI of cGVHD was 45%; mild and moderate cGVHD was observed in 82% of cases. Transplant from sibling donor and MAC regimen were associated to an increased risk of cGVHD. The 2-year OS according to modified MTSS was: 100% for low, 85% for intermediate and 50% for high risk (p=0.01).

Conclusions: In our experience, better outcome was observed for patient < 57-year-old, with higher PS, not progressing during Ruxolitinib treatment before HSCT. Modified MTSS was a robust tool for the evaluation of transplant risk.

Disclosure: Nothing to declare.

University Hospital Essen, Essen, Germany

Background: Tyrosine kinase inhibitors (TKI) have fundamentally changed the therapeutic concept in CML leading to excellent outcome. Although allogeneic stem cell transplantation (HSCT) is currently only required for a limited number of patients (pts) post-transplant relapse remains a major challenge.

Methods: Retrospective single center long-term evaluation of overall survival (OS), relapse-free survival (RFS) and the incidence of CML relapse after allo-HSCT. Analysis of OS and leukemia-free survival (LFS) among relapsed transplant recipients compared to non-relapse pts, review for prognostic factors and evaluation of response to relapse treatment. Data on 488 eligible CML pts transplanted between January 1996 and September 2015 were analyzed. At time of transplant 80% of all pts were in chronic, 12% in accelerated and 8% in blast phase. For the comparison between OS in pts with and w/o relapse after HSCT only survival longer than 15 months post-transplant (n=352) was considered to minimize lead-time-bias by landmark analysis. Cox regression was used to ascertain influencing factors for RFS.

Results: Median follow-up in the cohort was 129 months, 25% (n=120) of all transplant recipients sustained relapse with a median onset of 15 months after HSCT. Cumulative incidences (CI) of relapse were 13%, 23%, 26%, 28% and 30% after 1, 3, 5, 10 and 15 years post-transplant. RFS was assessed 67%, 53% and 47% after 1, 5 and 10 years post-transplant. Multivariate analysis of RFS proved advanced disease stages (> 1. chronic phase) at time of HSCT to be an independent adverse prognostic factor (p=0,005) whereas chronic GvHD showed only significant impact in univariate analysis. Based on landmark analysis, OS could be demonstrated to be significantly higher in transplant recipients w/o relapse (p=0,042). Among relapsed pts OS was significantly worse in hematologic compared to molecular or cytogenetic relapse (p=0,018; p=0,012). In 72% of pts with CML-relapse long-term remission could be induced resulting in a median progression-free survival of 98 months. For molecular relapse 15-year OS was 92% after discontinuation of immunosuppression, 100%, 89% and 80% after treatment with DLI, IFN or TKI. For cytogenetic relapse 15-year OS was 56% after discontinuation of immunosuppression and 100% after treatment with DLI, IFN or TKI. Hematologic relapse resulted in a 10-year OS of 100% after treatment with IFN and 67% after TKI therapy.

Conclusions: To achieve favorable RFS in CML, allo-HSCT should be applied in non-advanced disease stages. However, even in case of relapse after HSCT remissions with favorable long-term survival can be induced in particular when relapse is diagnosed as molecular or cytogenetic CML recurrence.

Disclosure: Nothing to declare.

Pavlov First Saint Petersburg State Medical University, Saint Petersburg, Russian Federation

Background: The overall therapeutic tactics strategy in CML patients has changed drastically after tyrosine kinase inhibitors (TKIs) were introduced. There is, however, a subgroup of advanced disease phase patients or patients with TKIs intolerance/ loss of response, in which the overall prognosis is dismal and allo-HSCT is the only curative option. As a large transplant center we have observed the overall treatment landscape change with new TKIs generations being introduced. This retrospective study summarizes our experiences in pre- and post-TKIs era.

Methods: Our retrospective cohort study includes allo-HSCT recipients with CML treated between 1995 and 2019 (n=114). The diagnosis was based on clinical and laboratory criteria. In all patients either Philadelphia (Ph) chromosome or chimeric BCR-ABL gene were found. Disease stage was determined according to WHO criteria. The chronic phase 1 (CP1) was confirmed in patients with no history of accelerated phase (AC) or blast crisis (BC), otherwise CP≥2 was confirmed. Pre allo-HSCT hematological, cytogenetic or molecular response was evaluated according to ELN criteria. The myeloablative conditioning regimen used consisted of 16 mg/kg of busulfan and 120 mg/kg of cyclophosphamide. However, 96% of patients received reduced intensity conditioning regimen with 180 mg/m² of fludarabine and 8-14 mg/kg of busulfan or 140 mg/m² of melphalan.

Results: The number of transplant-eligible CP1 patients decreased dramatically after TKIs introduction. While in 1995-2004 as much as 75% transplant recipients were in CP1 there were only 12% in 2017-2019. In recent years most CP1 patients scheduled for allo-HSCT (93%) have history of TKIs resistance, some also are transplanted after T315I mutation is found or due to treatment intolerance (7%). From 2008 on, there is also a concurrent trend for less CML patients receiving allo-HSCT in AP or BC (50% in 2008 and 21% in 2017-2019). Most of these patients reached CP≥2 on 1^st and 2^nd generation TKIs. Since 2004-2005 the CP≥2 patients’ proportion is consistently raising reaching as much as 65.6% in 2017-2019. Due to the targeted therapy improvement we are now able to achieve response even in BC patients. Therefore, the proportion of patients with BC history increased from 12% in 2004 to 60% in 2019, 20% of current allo-HSCT recipients having history of several BCs. The latter may point at a failure to refer a patient to allo-HSCT in time. Some recent years are marked by increase of 5-year overall survival (OS) from 25% to 58%, which may be explained by the fact that much less patients are now receiving allo-HSCT in AC or BC. A total of 46 patients in our cohort died, 29% of them (n=13) due to GVHD, 24% (n=11) of infectious complications, 39% (n=18) after disease relapse, 4% (n=2) due to heart attack, 4% (n=2) due to VOD.

Conclusions: The allo-HSCT belongs currently to 3^rd or 4^th line therapy for CP1 CML patients. It is also still a modality of choice if there is history of AC or BC. New generation TKIs are used to prepare patients for allo-HSCT thus raising significantly the CP≥2 allo-HSCT recipients proportion.

Clinical Trial Registry: NA

Disclosure: Nothing to declare.

University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom

Background: Despite recent advances in understanding the pathogenesis and molecular landscape of myelofibrosis over recent years, the condition continues to pose a number of challenges for the treating clinician. Allogeneic stem cell transplant remains the only potentially curative option, however, the heterogeneity in both clinical course and therapeutic response, as well as patients’ comorbidities, can make it difficult to weigh up the risks and benefits for individual patients. The advent of JAK inhibitors has revolutionized the treatment paradigm over the last decade with preliminary data suggesting positive impact on transplant outcomes. We conducted a retrospective review of patients undergoing a reduced-intensity Alemtuzumab- conditioned allogeneic stem cell transplant for myelofibrosis over a 9-year period, at Birmingham Heartlands Hospital, in order to provide real world data and identify any significant correlation between patient characteristics, JAK-2 inhibitor use, and outcomes.

Methods: We identified 27 patients (16 Male vs 11 Female, 8 sibling donor vs 15 matched-unrelated donor vs 4 mismatched-unrelated donor) who had undergone an allogeneic stem cell transplant for myelofibrosis at Heartlands Hospital between 16^th April 2010 and 7^th August 2019. 9 patients had received Ruxolitinib prior to allogeneic stem cell transplant. All patients were DIPS score intermediate 2/high. Data was obtained from transplant protocols, discharge letters and clinic letters accessed via the hospital online record system. The information was inputted onto an excel spreadsheet and statistical analysis was carried out using SPSS.

Results: Patients had a median age of 64.6 years and were followed up for a median of 23 months. Median overall survival for the cohort was 65.9%. (see figure 1)

25% patients developed acute graft versus host disease (GVHD) grade 3/4, including 2 patients who died of GVHD, and 14% patients developed chronic GVHD. Only 1 patient died of disease progression post transplant, a 2^nd patient progressed but regained remission with donor lymphocyte infusion (DLI) and ruxolitinib. Progression free survival was 62% at 23 months.

37% patients in total received DLI and 1 patient received a stem cell top up for secondary graft failure. 7.4% patients had a prior diagnosis of essential thrombocythemia, and 81% patients had neutrophil engrafted by day +28.

Sibling donors were associated with significantly better survival than matched unrelated donors (p=0.033). There was also a statistically significant improvement in survival in those patients who received DLI (p=0.037).

In our cohort, we did not identify any statistically significant correlation between prior ruxolitinib use and risk of death, progression, or acute and chronic GVHD.

Conclusions: Although patient numbers were small, our results highlight the curative potential of allogeneic stem cell transplantation in myelofibrosis using a reduced intensity approach with Alemtuzumab-based T-cell depletion. This approach is both safe and effective, even in a relatively older population, and the suggestion that post -transplant DLI may confer a survival benefit will need further evaluation in larger multicentre cohorts.

[Figure 1- overall survival]

Disclosure: Nothing to declare.

¹HELIOS Klinikum Berlin-Buch, Berlin, Germany, ²Universitätsmedizin Mannheim, Mannheim, Germany

Background: Systemic mastocytosis (SM) is characterized by proliferation and accumulation of clonal mast cells in bone marrow, skin and visceral organs. Bone marrow mast cell infiltration, elevated serum tryptase and a KIT D816V mutation (>90% of patients) are diagnostic hallmarks. The various subtypes of this rare haematological neoplasm are characterized by a more or less aggressive course. Targeted therapy against mutant-KIT with midostaurin has been approved, however, complete responses have not yet been reported and durable major response may only occur in 50-60% of patients. Cladribine has demonstrated efficacy in treatment of indolent SM and advanced SM (AdvSM) while allogeneic stem cell transplantation (ASCT) is a treatment option for eligible AdvSM patients with refractory or aggressive clinical course. In a retrospective study, response rates of 70% have been reported at day +100, followed by long term survival in 50-60% of patients.

Methods: We here report on ASCT in two patients (female, 70 years old; male, 50 years old) with aggressive SM and associated myelodysplastic/myeloproliferative neoplasm (ASM-MDS/MPN). The first patient presented with a bone marrow infiltration of 5%, a serum tryptase of 320 µg/l (normal value < 11.4), massive splenomegaly and multiple additional somatic mutations in ASXL1, SETBP1 and CSF3R in addition to KIT D816V. The second patient presented with a bone marrow mast cell infiltration of 80%, a serum tryptase of 540µg/l and only mild splenomegaly. Somatic mutations were identified in KIT D816V, NRAS and TET2. Both patients were resistant to midostaurin but achieved a stable partial remission on one and seven cycles cladribine, respectively. Bone marrow biopsy revealed residual mast cells of < 5% and serum tryptase was decreased to 52µg/l and 102µg/l when conditioning therapy with fludarabine (150mg/m2), treosulfan (36g/m2) and ATG Neovii® (45mg/kgBW) was initiated. Peripheral stem cells from unrelated 10/10 donors were used as stem cell source. While one patient had negligible skin reactions associated to the central line, the second patient presented with high fever and rash one week after transplantation mimicking hyperacute GvHD, which was, however, most likely an associated with mediator release/allergic reaction upon antimycotic treatment with an echinocandin.

Results: Both patients show complete chimerism on day +100, tryptase is normal in the first patient and near normal (35µg/l) in the second patient. The first patient shows mild mucocutaneous chronic GvHD.

Conclusions: Our experience shows feasibility and short-term efficacy of ASCT in ASM-AHN after induction of best possible remission with several cycles of cladribine and treosulfan-based conditioning. Mediator release may remain an important issue during and after transplantation and its differentiation from GvHD may be difficult.

Disclosure: Nothing to declare.

¹San Gerardo Hospital, Monza, Italy, ²University of Milano-Bicocca, Monza, Italy

Background: Allogeneic Stem Cell Transplantation (ASCT) is the only curative option for Myelofibrosis (MF). Development of reduced intensity conditioning (RIC) regimens and introduction of Ruxolitinib (Rux) have improved the outcome of ASCT. However, this procedure is still burdened by substantial morbidity and high transplant-related mortality (TRM). Here we report our experience with ASCT in MF setting, in order to evaluate the factors influencing post-transplant outcome, in term of overall survival (OS) and Progression-free survival (PFS).

Methods: In the last 10 years we performed 30 ASCT on 27 MF patients (pts); 3 pts of them received a second ASCT for MF relapse. The median age was 51 (range: 25-68) years. Driver mutations were found in 23 pts and were: JAK2V617F in 16 (59%), MPL in 3(11%) and CALR mutations in 4 (15%) pts; 4 (15%) pts were defined as “triple-negative”. According to Dynamic International Prognostic Scoring System (DIPSS) at transplant, pts were stratified into high, intermediate-2 and intermediate-1 risk in 11 (41%), 12 (44%) and 4 (15%) cases, respectively. Considering the first ASCT, donors were matched related (MRD), matched unrelated (MUD) and haploidentical in 18 (67%), 7 (26%), and 2 (7%) of cases, respectively. Conditioning regimen (CR) was RIC in 11 pts (41%) or myeloablative in 16 pts (59%); all CR were Busulfan and Fludarabine-based, in 48% of cases (n=13) associated with Tiothepa. Conventional GVHD prophylaxis regimens were used according to type of ASCT. Splenectomy or spleen irradiation were performed before ASCT in 2 and 6 pts in pre-Rux era; 16 pts (59%) received Rux before ASCT. Source of stem cells were bone marrow in 15 (56%) or peripheral blood stem cells in 12 (44%) pts. OS and PFS have been evaluated by Kaplan-Meier analysis.

Results: Aafter a median follow-up of 18.5 (range: 0.5 - 175) months from first ASCT, 4/27 pts (15%) died for early TRM, 6 (22%) pts for MF relapse (4) or leukemic evolution (2). 17 (63%) pts were alive, 15 of them with full chimerism and complete remission (one after the second ASCT); 2 pts were alive in MF relapse. Chronic GVHD occurred in 6 (22%) pts.

The probability of OS for the entire cohort at 2 and 5 years was respectively 75% and 60% and the 2 and 5 year PFS was 75% and 55% respectively. In statistical analysis, significant predictive factors of good outcome were: intermediate-1 DIPSS score at transplant, Rux-exposition pre-transplant and development of chronic GVHD. There was no correlation between clinical outcome and type of driver mutations, age at transplant, donor type, CR, source of stem cells.

Conclusions: ASCT in MF is actually a valid therapeutic option for pts eligible to the procedure also in the Rux era. In our experience, earlier stage of MF at time of transplant and Rux exposition before transplant seem to have a favourable impact on the outcome post-ASCT; also a chronic GVHD seems to play a protective role for reducing relapse risk post-ASCT.

Disclosure: Nothing to disclose

Almazov National Medical Research Centre, Saint-Petersburg, Russian Federation

Background: Allogeneic hematopoietic stem cell transplantation (alloHSCT) is currently considered a mandatory therapy option in patients with refractory to at least two of tyrosine kinase inhibitors (TKI). Haploidentical alloHST are becoming increasingly important in this cohort of patients.

Methods: 33 years old, male. History of CML: blast crisis as a debut; the disease was characterized by primary cytogenetic resistance to imatinib and bozutinib. In the study of BCR-ABL mutations during bozutinib therapy, the T315I mutation was detected. The loss of complete hematological response (CHR) was stated with the preservation of the chronic phase (CP) of CML; cytoreductive therapy with hydroxyurea 3000 mg/day was added to bozutinib. Patient only had one haploidentical donor (mother).

When CHR was achieved, alloHSCT was performed (period from disease debut to alloHSCT is 58 months). Conditioning regimen (CR):fludarabine 150 mg/m2, busulfan 8 mg/ kg; prophylaxis of the graft-versus-host disease (GVHD): high-dose (50 mg/kg DD3,4) cyclophosphamide was administered, tacrolimus and mycophenolate mofetil therapy was initiated at D5. To D+30 the patient had 100% donor chimerism, Ph-chromosome in cytogenetic studies of bone marrow was not determined, but minimal residual disease (MRD) remained-0,210% BCR-ABL p210 (15349 ABL copies). Prophylactic therapy with TKI- dasatinib 50 mg/day was initiated at D+58. From D+62, there was a decrease in donor chimerism: 93.8% (D+62) => 91.5% (D+82) => 91.6% (D+118), MRD by these terms decreased by 1 log. By D+128 immunosuppressive therapy (IST) was withdrawn. From D+148: deepening profundity of persistent cytopenia, decreasing of donor chimerism to 82%. Infusion of donor lymphocytes (DLI) - 1*10^6 CD3+CD45+/kg was performed on D+152. Total bone marrow hypoplasia, decreasing of donor chimerism to 33.5% were detected on D+158. The secondary graft failure was stated.

Results: Second alloHSCT from the same donor was performed within 7 days after the diagnosis of secondary graft failure. CR: fludarabine 150 mg/m2, melphalan 140 mg/m2; prophylaxis of GVHD was the same. On D+29 100% donor chimerism was detected, BCR-ABL p210-0% (11212 ABL copies). By D+63 decreasing of donor chimerism to 93,3% was stated, on D+63 IST was completely withdrawn. On D+78, donor chimerism increased up to 98%. On D+83, due to high risk of secondary graft failure, DLI was performed (5*10^5 CD3+CD45+/kg). On DD+110, +137 full donor chimerism was defined. MRD was not detected during the entire post-transplant period, and therefore prophylactic administration of TKI was not resumed. To date, chronic multilocus GVHD (skin, mucosa, liver) has occurred, which was successfully treated with ruxolitinib and extracorporeal photopheresis.

Conclusions: Allogeneic (haploidentical) HSCT in patients with refractory CML may be a successful alternative to a fully HLA-compatible SCT. Second allogenic (haploidentical) HSCT from the same donor with the change of CR in our patient was effective. As a stimulation of the graft-versus-leukemia (GVL) effect, "earlier” withdrawal of IST and DLI may be successfully performed. “Deep molecular response” in post-transplant period can be achieved without administration of TKI due to satisfactory graft function. Ruxolitinib is actively used in GVHD treatment, and can also stimulate an antitumor response.

Earlier alloHSCT can contribute to reduce incidence of complications.

Disclosure: Nothing to declare.

Conditioning regimens

¹Prinses Maxima Centre for Pediatric Oncology, Utrecht, Netherlands, ²University Medical Center Utrecht, Utrecht, Netherlands, ³Leiden University Medical Center, Leiden, Netherlands, ⁴Memorial Sloan Kettering Cancer Center, New York, NY, United States

Background: The combination of Clofarabine + Fludarabine + Busulfan (CloFluBu) was found to have synergistic anti-leukemic activity against ALL and AML blasts in vitro (Andersson et al: BBMT 2011). As TBI induces significant late effects in childhood ALL, and AML patients have high relapse rates, we hypothesized that CloFluBu may be a potential alternative to TBI in ALL, and could add anti-leukemic activity in AML. Within the “Dutch COG HCT Working Group” we prospectively studied the outcomes of a CloFluBu-conditioning regimen for lymphoblastic and myeloid malignancies.

Methods: Patients from the 2 pediatric HCT programs (LUMC and UMC Utrecht/Princess Máxima Center for Pediatric Oncology) in the Netherlands with a lymphoblastic or myeloid malignancy receiving their first HCT, between August 2011 and April 2019, were included. Over 4 days, Clofarabine 30mg/m2 was given in 1 hour, followed by Fludarabine 10mg/m2 in 1 hour, followed by a 3-hour infusion of once-daily targeted Busulfan (weight-based dosing + therapeutic drug monitoring to a total Bu-exposure of 90mg*h/L). Thymoglobulin was added in unrelated donors (except in AML patients receiving cord blood). GvHD-prophylaxis was according to standard protocols. Minimal Residual Disease (MRD) negative was defined as < 10e-4. Primary endpoints were Overall Survival (OS) and Leukemia Free Survival (LFS). Secondary endpoints were Non Relapse Mortality (NRM), Relapse, acute and chronic Graft-versus-Host Disease (GvHD), and VOD/SOS. Cox Proportional Hazard and fine and gray competing risk models were used for data analysis.

Results: 155 children were included; 66 ALL (38 in CR1, 28 ³ CR2), 69 AML (28 in CR1, 40 in CR2, 1 in active disease) and 20 other malignancies (mostly MDS-EB). Median age was 9.7 (0.5-18.6) years. Most donors were unrelated (119 vs 36 related); 79 Bone Marrow (BM), 66 Cord Blood (CB) and 10 Peripheral Blood Stem Cells. Median follow up was 964 (19-2994) days. Overall the 3-yr estimated OS and LFS was 72 ± 4.5% and 65 ± 5% respectively. Estimated 3-yr LFS for MRD-neg ALL, MRD-pos ALL, AML CR1 and AML CR2 was 74 ± 7%, 40 ± 12%, 64 ± 10%, 65 ± 9% respectively). NRM in whole cohort was 10.3 ± 3.0% (with 25 ± 4.3% for AML CR1 (n=28), and 5.8 ± 2.3% in the rest). Other endpoints: only 2 graft-failures were noted, incidence of aGvHD III-IV at 6 months was 11 ± 3%, extensive chronic GvHD at 3-yr was 5.2 ± 2.2%. Relapse at 3-yr was 25 ± 4.3% (MRD-neg ALL 16.2 ± 3.7%, versus 60 ± 4.9% in MRD-pos ALL, in AML 22.5 ± 4.2%) and no VOD/SOS was noted.

Conclusions: CloFluBu in myeloid- and lymphoblastic malignancies, showed very limited toxicity and encouraging LFS in all groups, in particular for MRD negative ALL. More studies, preferably in randomized controlled clinical trials, are needed to draw firm conclusion with regards to the anti-leukemic effect and late effects.

Clinical Trial Registry: N/A

Disclosure: nothing to disclose

¹Hematology and Stem Cell Transplant Center AORMN, Pesaro, Italy, ²Carreggi Hospital, Firenze, Italy, ³IRCCS Casa Sollievo della Sofferenza Hospital, San Giovanni Rotondo, Italy, ⁴Ospedali Riuniti, Ancona, Italy, ⁵San Martino Hospital, Genova, Italy, ⁶La Sapienza University, Roma, Italy, ⁷AOU di Udine, Udine, Italy, ⁸Santa Maria delle Croci di Ravenna, Ravenna, Italy, ⁹Spirito Santo Hospital, Pescara, Italy, ¹⁰Piacenza Hospital, Piacenza, Italy, ¹¹IRST, Meldola, Italy, ¹²IRCCS Regina Elena Institution, Roma, Italy, ¹³Mazzoni Hospital, Ascoli Piceno, Italy, ¹⁴AOU Policlinico di Bari, Bari, Italy, ¹⁵Infermi Hospital, Rimini, Italy, ¹⁶Sant’Orsola Hospital, Bologna, Italy, ¹⁷Carlo Bo University, Urbino, Italy

Background: A major drawback affecting clinical trials of high-dose therapy (HDT) followed by autologous stem cell transplant (ASCT) in lymphomas is the high heterogeneity of histological entities. As a consequence, the statistical power is reduced when we focus on a specific histological subset, and data are often not conclusive. We designed a phase II study to evaluate the efficacy of the BeEAM conditioning (bendamustine 200 mg/m2 on days -7,6, cytarabine 400 mg/m2 days -5-4-3-2, etoposide 200 mg/m2 days -5-4-3-2, melphalan 140 mg/m2 day-1) in resistant/relapsed diffuse large B-cell non-Hodgkin lymphoma (DLBCL) patients.

Methods: The study was registered at European Union Drug Regulating Authorities Clinical Trials (EudraCT) N. 2011-001246-14. 64 patients (median age 54.5 years, range 19-70) with resistant/relapsed DLBCL or transformed follicular lymphoma were enrolled. The primary end-point of the study is to evaluate the 1-year complete remission rate.

Results: Briefly, 47/64 patients had advanced stage disease (III-IV); 21 were primary refractory and 43 had relapsed. 33/64 were in II or subsequent CR after salvage therapy, whereas 24 were in PR and 7 in progressive disease. A median number of 5.55x10⁶ CD34+/Kg cells (range 2.07-12.20) collected from peripheral blood was reinfused to patients. All patients engrafted, with a median time to ANC>0.5x10⁹/l of 10 days. Median times to achieve a platelet count >20x10⁹/l and >50x10⁹/l were 13 and 18 days respectively. Twenty-four out of 64 patients presented a FUO (37.5%). One patient died due to an incomplete hematological recovery after transplant and one patient died due to acute liver failure, producing an overall transplant related mortality of 3.1%. Sixty-two patients are evaluable for response: 51/62 (82%) obtained a CR, 4/62 (6%) a PR, whereas 7/62 (11%) did not respond to therapy. The median follow-up after transplant was 34 months (range 1-90).

Conclusions: The stringent inclusion criteria at enrollment allow to precisely evaluate the impact of HDT with Bendamustine followed by ASCT in a highly selected population of patients with DLBCL. The 1 year remission rate was superior to 55%, thus reaching the primary end-point. Accordingly, our data provide the evidence that the Benda-BEAM regimen is safe and has promising high efficacy in resistant-relapsed aggressive diffuse large B cell lymphoma.

Disclosure: Nothing to declare.

University of Freiburg Medical Center, Freiburg, Germany

Background: The age of patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) has increased during the last decades, mainly due to improved reduced intensity/toxicity conditioning protocols. A reduced-intensity conditioning based on fludarabin, carmustin/BCNU and melphalan (FBM) has been previously developed at our institution. Since we observed detrimental effects in patients with compromised lung function prior allo-HCT and conditioned with FBM, efforts have been made in order to replace BCNU by thiotepa (FTM) to reduce toxicity.

Methods: In this study, we retrospectively analyzed the outcome, Graft-versus-Host (GvHD) incidence, lung function and organ toxicity of patients transplanted at our institution after conditioning with the reduced intensity/toxicity protocols FBM (n=122) and FTM (n=73) between January 1^st 2013 and December 31^st 2017. Patients were stratified by caring physicians to receive conditioning according to FBM protocol (fludarabine 4x30mg/m², BCNU/carmustine 2x150mg/m² and melphalan by patients >55 years:1x110mg/m² or < 55 years:1x140mg/m²) or FTM (fludarabine 4x30mg/m², thiotepa 2x5 mg/kg and melphalan for patients >55 years:1x110mg/m² or < 55 years:1x140mg/m²). We included in the analysis all patients at first allo-HCT and surviving at least 100 days after allo-HCT. During the observation period, continuously increasing number of patients were treated with FTM. Therefore, patients treated with FBM had a longer median follow-up of 957 (range 104 -2337) vs. 801 days (range 124 -1667) of FTM-treated patients.

The Cox proportional hazards regression model was used to estimate hazard ratios (HR) and confidence intervals (CI) for overall survival and progression-free survival. We applied the Fine and Gray model to compare cumulative incidence rates in the presence of competing risks and presented as subdistribution hazard ratios for relapse incidence, non-relapse mortality, aGvHD and cGvHD incidence. Pearson’s chi-square and Fisher’s exact tests were used to compare categorical variables as appropriate and Student’s T-test to compare continuous variables.

Results: Compared to patients conditioned with FBM, FTM-treated patients were younger and received less frequently GvHD prophylaxis with alemtuzumab. Patients treated with FTM suffered more frequently lymphoid malignancies and received more chemotherapy cycles. As expected, there were more patients with a HCT-CI score ≥ 4 and with impaired lung function allocated in the FTM group, due to the patient selection by caring physicians to the presumably less pulmonary toxic protocol.

Despite a higher comorbidity-index prior allo-HCT, patients conditioned with the FTM protocol show similar overall survival and relapse incidence. Hence, patients with impaired lung function prior allo-HCT, as defined by FEV1< 80% of predicted or DLCOcSB< 80% of predicted, and conditioned with FTM had a 2-year overall survival of 83.0% compared to 71.1% of FBM-treated patients (p=0.11). FTM-treated patients had less pulmonary cause of death compared to patients treated with FBM. In contrast, gastrointestinal complications were more frequently observed in patients conditioned with FTM. No differences were observed in incidence and severity of acute and chronic GvHD. Lung function was reduced in FTM-treated patients prior allo-HCT and 1 year after allo-HCT compared to FBM-treated patients.

Conclusions: In summary, the FTM protocol has reduced toxicity but sufficient anti-neoplastic effect and is suitable for patients with impaired lung function prior allo-HCT.

Disclosure: Nothing to declare.

¹Imperial Healthcare Trust, London, United Kingdom, ²Imperial College London, London, United Kingdom, ³Guy’s and St. Thomas’ NHS Foundation Trust, London, United Kingdom

Background: Haematopoietic stem cell transplantation (HSCT) in advanced cutaneous T-cell lymphomas (CTCL), of which mycosis fungoides (MF) and Sezary syndrome (SS) are the most common subtypes, is increasingly practiced as a curative therapy. Minimal-intensity conditioning, using a protocol established in Stanford using anti-thymocyte globulin (ATG) and total nodal lymphoid irradiation (TNLI), is an option for CTCL patients, particularly those of older age, and those with chronic colonisation of skin lesions by potentially multi-resistant organisms which would render myeloablative conditioning regimens higher risk. The conditioning protocol comprises initial total skin electron beam therapy (TSEB) (4-8 week course) pre-transplant, followed by TNLI (day -11 to day 0), 10 x in 80cGy fractions of 4 radiation fields (2 anterior and 2 posterior including all major lymphoid areas) and ATG (day -11 through day -7, 1.5mg/kg/day). Ciclosporin was given from day -3 onwards, MMF was given from day +1 onwards. The benefits of this protocol include reduced incidence of acute GvHD and prompt multi-lineage engraftment, with evident graft vs tumour effect.

Methods: This is retrospective case series of 32 CTCL patients who underwent allogeneic transplant for advanced CTCL using the TSEB/ATG/TNLI protocol at a single centre after failure of standard therapy between 2012 and 2019. Of the 32 patients, 3 had SS and 29 of had MF. The number of prior treatments ranged from 3-8. 11 patients had matched sibling allografts, 2 patients had haploidentical sibling allografts and 19 patients had grafts from matched unrelated donors. We used the patients’ transplant protocols and hospital electronic records to retrieve information. We collected data for DFS and OS analyses as well as transplant-related mortality, and the doses and responses to donor lymphocyte infusions (DLI).

Results: We used the Kaplan Meier method to generate survival curves looking at time to two events; disease-free survival (DFS) and overall survival (OS). Of the 32 patients who were transplanted, 14 patients relapsed, of which 4 then died due to the disease progression. 7 patients received at least one DLI post-transplant, either for relapsed disease or falling chimerism, and 4 were successfully salvaged with DLI and chemotherapy/radiotherapy. An additional 5 patients died due to sepsis/GvHD. 13 patients remain in remission. The Kaplan Meier estimates of 5-year OS and 5-year DFS in this study were 63% and 45%, respectively.

Conclusions: Use of this minimally intensive protocol resulted in a predicted OS of 2/3 of patients at 5 years with approximately half of the patients being disease free, suggesting promising long-term outcomes in a disease with otherwise poor overall survival. This study has shown successful engraftment can be achieved with this minimally-invasive protocol and suggests reducing the risk of non-relapse related mortality can be achieved without increasing risk of relapse or progression. For those who relapse DLI may be of benefit and further study of its use in this setting is recommended.

[Kaplan Meier Survival Curves]

Disclosure: Nothing to declare.

¹Ancona University Hospital, Ancona, Italy, ²Saint Antoine Hospital, Paris, France, ³HUCH Comprehensive Cancer Center, Stem Cell Transplantation Unit, Helsinki, Finland, Helsinki, Finland, ⁴Hopital St. Louis, Paris, France, ⁵University Hospital Eppendorf, Hamburg, Germany, Hamburg, Germany, ⁶CHU Bordeaux, Hôpital Haut-leveque, Bordeaux, France, ⁷St. James`s Hospital, Dublin, Ireland, ⁸Dél-pesti Centrumkórház - OrszágosHematológiaiésInfektológiaiIntézet, Budapest, Hungary, ⁹Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, The Netherlands, Rotterdam, Netherlands, ¹⁰Bristol Royal Hospital for Children, Bristol, United Kingdom, ¹¹CHU de Lille, LIRIC, INSERM U995, Université de Lille, Lille, France, ¹²Centre Hospitalier Universitaire de Rennes, Rennes, France, ¹³Vanderbilt University Medical Center, Nashville, TN, United States, ¹⁴Chaim Sheba Medical Center, Tel-Hashomer, Israel

Background: We report here the results of a retrospective study designed to evaluate outcome of ALL patients undergoing allo-HCT with KPS score ≤80%.

Methods: The analysis included ALL patients aged ≥18 years, undergoing allo-HCT in first remission between 2000 and 2018, with a KPS score of 50% to 80% at the time of transplant. Patients who received manipulated grafts or had incomplete data about cytogenetics were excluded. Conditioning intensity was defined according to EBMT definitions (Aoudjhane M. et al, Leukemia 2005; 19: pp. 2304-2312).

Results: A total of 1,010 patients were identified. Median age at transplant was 43 years (18-76 years). Median year of transplant was 2011. The KPS score was =80% in 83% of the patients and < 80% in 17% of the patients. Diagnosis was Philadelphia chromosome (Ph) negative B-ALL, Ph positive B-ALL or T-ALL in 34%, 44% and 22% of the patients, respectively. Donor type was MSD or 10/10 UD in 60% and 40% of the patients, respectively. Conditioning was myeloablative (MAC) or reduced-intensity (RIC) in 78% and 22% of the patients, respectively, and it was TBI-based in 79% of the patients. Stem cell source was PBSC in 76% and BM in 24% of the patients, respectively. Anti-thymocyte globulin (ATG) was administered to 21% of the patients receiving MSD and 68% of the patients receiving 10/10 UD as donor type. Cumulative incidence of grade II-IV and III-IV aGVHD was 32% and 9%, respectively. The 2-year cumulative incidence of chronic GVHD (cGvHD) and severe cGVHD was 43% and 18%, respectively. Non relapse mortality (NRM) and relapse incidence (RI) at 2 years were 18% and 28%, respectively. At 2 years, leukemia-free survival (LFS), overall survival (OS) and GVHD-free, relapse-free survival (GRFS) rates were 54%, 64% and 41%, respectively.

On multivariate analysis, transplant from 10/10 UD was associated with higher incidence of aGVHD (HR 1.8, p< 0.0001) and higher risk of NRM (HR 1.7, p< 0.01) as compared to MSD. RIC conditioning was associated with higher risk of relapse (HR 1.2, p=0.02), lower LFS (HR 1.3, p=0.03) and lower GRFS (HR 1.3 p=0.02) as compared to MAC. NRM was not significantly different between MAC and RIC. Factors independently associated with improved OS were younger age at transplant, female sex, more recent year of transplant and Ph+ B ALL phenotype. Administration of ATG was associated with reduced risk of developing grade II-IV aGVHD (HR 0.6, p< 0.001), cGVHD (HR 0.5, p< 10^-4) and severe cGVHD (HR 0.4, p< 10^-4).

Conclusions: In conclusion, allo-HCT is feasible in patients with acute lymphoblastic leukemia in first remission and KPS score ≤80%, with acceptable NRM and survival rates. Transplant from a sibling donor was associated with reduced risk of NRM and aGVHD as compared to matched unrelated donor. Interestingly, despite the poor KPS score of the patients included in the analysis, a MAC protocol was associated with similar NRM, lower relapse and better LFS and GRFS as compared to RIC in the selected population. Finally, administration of ATG was associated with reduced acute and chronic GVHD rates.

Disclosure: Nothing to declare.

¹CIBMTR (Center for International Blood and Marrow Transplant Research), Medical College of Wisconsin, Milwaukee, WI, United States, ²Medical College of Wisconsin, Milwaukee, WI, United States, ³Princess Margaret Cancer Center, Toronto, Canada, ⁴University of Florida, Gainesville, FL, United States, ⁵University of Virginia Health System, Charlottesville, VA, United States, ⁶Loyola University Medical Center, Maywood, IL, United States, ⁷Memorial Sloan Kettering Cancer Center, New York, NY, United States, ⁸City of Hope, Duarte, CA, United States, ⁹University of Texas MD Anderson Cancer Center, Houston, TX, United States, ¹⁰Winship Cancer Institute of Emory University, Atlanta, GA, United States, ¹¹Swedish Orphan Biovitrum (Sobi), Stockholm, Sweden

Background: Incidence of debilitating oral mucositis (OM) can be as high as 99% after myeloablative conditioning regimens preparing patients with hematologic malignancies for hematopoietic cell transplant (HCT). Palifermin is a recombinant human keratinocyte growth factor that stimulates proliferation and differentiation of epithelial cells. In randomized controlled trials, palifermin reduced incidence and duration of severe OM in patients with hematologic malignancies receiving myelotoxic therapy in the setting of autologous hematopoietic cell support. Long-term safety of palifermin or the potential risk of stimulation of new malignancies (NM), however, has not been well established.

Methods: In this long-term, prospective, matched cohort study, patients who received palifermin and underwent autologous or allogeneic HCT for hematologic malignancies from 2006-2013 were 1:1 matched to patients who did not receive palifermin. Subjects were matched on age, HCT type, donor type, HCT date, disease type, disease status, region, and whether TBI was included in the conditioning regimen. Primary outcomes were overall survival (OS), relapse, and NM.

We adjusted for imbalances with a propensity score, modeled by logistic regression. The following covariates were used to identify factors associated with treatment assignment: age, race, disease, disease status, time from diagnosis to HCT, prior radiotherapy, type of HCT, growth factors use, graft source, donor age, donor-recipient sex and cytomegalovirus (CMV) serostatus match, conditioning regimen, graft-vs-host disease (GVHD) prophylaxis, year of HCT, and region. Equal propensity scores in both groups predicted they were equally likely to be treated with palifermin. Relative risks were estimated using Cox proportional hazards regression analysis, stratifying on the matched pair and considering the propensity score as a continuous covariate.

[Figure 1 overall survival; Figure2 New Malignancy]

Results: The analysis population consisted of 2191 matched pairs. The median follow-up was 8 years (range, 1-12.5 y), with excellent completeness of data across both arms (93% at 8 y). Overall, the median age was 51 y (range, < 1-80 y). HCT for acute leukemia was the most common indication (40%), followed by plasma cell disorder (28%), and non-Hodgkin lymphoma (13%). TBI was used in 41% of conditioning regimens. Fifty percent of the matched pairs underwent allogeneic HCT, and the two most common donor types were identical siblings (37%) and well-matched unrelated donors (35%). Among allogeneic HCT recipients, the majority (88.5%) received myeloablative regimens. In multivariate analyses, the relative risks of OS, relapse, and NM were not statistically significantly different between those who received palifermin and those who did not (relative risk [RR] for OS 1.01 (95% confidence intervals [CI] 0.91-1.12); RR for relapse 1.06 (95% CI 0.94-1.18); RR for NM 0.89 (95% CI 0.67-1.18)) (Figures 1, 2). The potential interactions between receiving palifermin and propensity score were tested, and no interactions were detected.

Conclusions: Long-term safety of palifermin was confirmed with no increased risk of overall mortality, relapse or NM.

Clinical Trial Registry: Not applicable

Disclosure: Swedish Orphan Biovitrum (Sobi) contracted with CIBMTR for services associated with fulfillment of the LTFU study. CIBMTR aligns all activities through the lens of its research mission and utilizes funding sources only to expand research infrastructure and to facilitate a broad research portfolio. It contractually maintains independent review and publication rights and, as such, does not consider the services provided to be a conflict of interest.

Kullenberg and Rudebeck are employees and shareholders of Sobi.

Dr. Perales reports honoraria from Abbvie, Bellicum, Celgene, Bristol-Myers Squibb, Incyte, Merck, Novartis, Nektar Therapeutics, Omeros, and Takeda. He serves on DSMBs for Cidara Therapeutics, Servier and Medigene, and the scientific advisory boards of MolMed and NexImmune. He has received research support for clinical trials from Incyte, Kite/Gilead and Miltenyi Biotec. He serves in a volunteer capacity as a member of the Board of Directors of American Society for Transplantation and Cellular Therapy (ASTCT) and Be The Match (National Marrow Donor Program, NMDP), as well as on the CIBMTR Cellular Immunotherapy Data Resource (CIDR) Committee.

¹Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Weill Cornell Medical College, Cornell University, New York, NY, United States

Background: High dose chemotherapy with BEAM (Carmustine, etoposide, cytarabine and melphalan) is a standard regimen for autologous hematopoietic cell transplantation (AHCT) in lymphoma patients. Multiple myeloma studies have shown that dosing melphalan as a fixed dose based on body surface area leads to inter-patient differences with a 5-fold variability in area under the curve (AUC), with higher AUCs associated with improved outcomes but increased toxicity. In this study, the pharmacokinetics (PK) of Evomela® (propylene glycol free melphalan, PGF-MEL) in BEAM, and its associations with outcome and toxicity were evaluated.

Methods: On D-1 prior to AHCT, 140 mg/m2 of PGF-MEL was given over 30 minutes and serum sample were drawn serially at 5, 15, 30, 40, 75, and 150 minutes after the dose. AUC PK modeling was done with Cetara Phoenix WinNonlin, Princeton, NJ. Toxicity collection is ongoing using CTCAE v4 through D+100 after AHCT.

Results: Eighty-seven patients that received BEAM conditioning between 08/2016 and 09/2019 had melphalan PK analysis. The median age was 51 (range, 19-74), 62% were male, and 53% had aggressive B-cell lymphoma. The median PK parameters were as follows: AUC 8.1 mg*h/L (range, 3.8-18.8); clearance 31.8 L/h (range 16.4-79.1); volume of distribution 33.2 L (range, 19.7-70.1); and half-life of elimination 0.7 hours (range, 0.5-1.7). The median dose of melphalan given was similar between patients ≤ median AUC and those above (260 mg [range, 200-340 mg) and 270 mg [range, 210-340 mg], respectively.) With a median follow up of 8.94 months (range 0.72-32.91) in survivors, univariate analysis showed no difference in 1-year overall survival (OS) (95.5% [84-100%] vs. 87.4% [76.5-100%], p=0.2) or progression-free survival (PFS) (78.4% [63.6-96.6%] vs. 78% [63.7-95.5%], p>0.99) when evaluating patients ≤ or above median melphalan AUC, respectively. Patients with a melphalan AUC ≤ the median had an average length of stay of 19 days (range, 5-27) vs. 21 days (range, 7-38) for those above the median exposure (OR 1.19 [1.05-1.38], p = 0.004). Toxicity data collection is ongoing.

Conclusions: Melphalan exposure ≤ 8.1 mg*h/L resulted in a shorter length of hospitalization likely driven by less toxicities, that will be reported upon completion of toxicity collection. Despite early results showing no difference in OS and PFS, the 5-fold variability seen with PGF-MEL AUC suggests that a sweet spot to optimize outcomes and minimize toxicities is needed.7

[Table 1. Baseline Characteristics]

Clinical Trial Registry: n/a

Disclosure: Valkal Bhatt (Incyte)

Miguel Perales (MolMed, NexImmune, Abbvie, Bellicum, Bristol-Myers Squibb, Incyte, Nektar Therapeutics, Novartis, Omeros, Takeda, Kite, Merck, Servier, Medigene)

Craig S. Sauter (Juno Therapuetics, Sanofi-Genzyme, Celgene, Spectrum Pharmaceuticals, Novartis, Genmab, Precision Biosciences, Kite, a Gilead Company, Gamida Cell, Pfizer, GSK)

Gunjan L. Shah (Janssen, Amgen)

¹MedicalPark Göztepe Hospital, İstanbul, Turkey, ²Bahcesehir University, İstanbul, Turkey, ³MedicalPark Antalya Hospital, Antalya, Turkey

Background: Pediatric patients with acute lymphoid leukemia (ALL) mainly receive myeloablative conditioning regimens based on total body irradiation (TBI) or chemotherapy (CHT) including busulfan before allogeneic hematopoietic cell transplantation (allo-HSCT). Due to severe long term complications of TBI, CHT-based conditioning has been preferred in many centers for pediatric patients. But there is lack of data about the early complications of allo-HSCT comparing TBI vs CHT.

Methods: To compare early complications of TBI and CHT consisting of busulfan, fludarabine and thiotepa conditioning regimens, we performed a retrospective analysis of single center registry data collected between 1^st of January, 2015 and 30^th of June, 2019 to assess the outcomes of patients receiving these regimens before an allo-HSCT. Variables associated with early complications of allo-HSCT (only in the first 100 days after transplant) and hence included into the analysis were: engraftment time, engraftment syndrome, acute graft versus host disease (aGVHD) grade 2-4, veno-occlusive disease (VOD), capillary leakage syndrome (CLS), thrombotic microangiopathy (TMA), cytomegalovirus (CMV) reactivation, bloodstream infection (BSI), hemorrhagic cystitis and posterior reversible encephalopathy syndrome (PRES).

Results: The characteristics of 72 patients was revealed in Table 1. These two conditioning regimens (CHT, n: 50; TBI, n: 22) were compared in pediatric ALL patients aged 18 years or younger at the time of transplantation in complete morphological remission (CR) (CR1, n: 40/CR2, n: 30/>CR2, n: 2). The incidences of aGVHD grade 2-4, VOD, CLS, TMA, BSI, hemorrhagic cystitis and PRES before day 100 were similar for both conditioning regimens; however, patients received TBI-based conditioning had significantly longer neutrophil engraftment time (17.5 vs 13 days, p: 0.001) and tended to have more engraftment syndrome (45.5% for TBI vs 24.0% for CHT, p: 0.069). Multivariate analysis showed that TBI-based conditioning was associated with a longer neutrophil engraftment time (HR: 1.20, p: 0.006), more CMV reactivation (HR: 3.65, p: 0.038) and more engraftment syndrome (HR: 3.18, p: 0.078). At the time of last follow-up, 59 patients were alive. Four patients died of disease progression and infection (n: 4) was the most common cause of non-relapse mortality (NRM). With a median follow-up of 25 months (2-45 months), 3 year-overall survival (OS) and -event-free survival (EFS) were 79.1% (95% CI 68.9-89.4). There was no survival advantage between two conditioning regimens [84.2% (95% CI 67.7-100.0) for TBI and 77.0% (95% CI 64.2-89.7) for CHT, p: 0.538]. Cumulative incidence of relapse (CIR) and NRM were 11.9% (95% CI 6.2-22.4) and 14.0% (95% CI 7.6-26.0), respectively, for all patients. Both groups showed a similar CIR and NRM [CIR, 5.0% (95% CI 0.7-37.1) for TBI and 6.6% (95% CI 2.2-19.7) for CHT, p: 0.844; NRM, 10.2% (95% CI 2.7-38.3) and 15.7% (95% I 7.9-31.5), respectively, p: 0.588].

Conclusions: Although this retrospective registry-based analysis has several limitations, both conditioning regimens showed a similar early complications profile. Conditioning by TBI demonstrated longer neutrophil engrafment time and more CMV reactivation in comparison to CHT and also there is a tendency for engraftment syndrome with TBI based conditioning. Comparison of these conditioning regimens warrant further evaluation in a prospective manner.

Disclosure: Nothing to declare.

¹King’s College Hospital, London, United Kingdom, ²King’s College London, London, United Kingdom

Background: Alemtuzumab is a monoclonal anti-CD52 antibody, a pan-lymphodepleting immunosuppressive agent in common use as part of conditioning for allogeneic stem cell transplantation (Allo-HSCT) in United Kingdom and many other centres across the globe, with benefits related to reduced graft versus Host disease (GVHD) and lower non-relapse mortality (NRM). However, evidence for effective dose schedule in Allo-HSCT remains debatable with some concerns related to delayed immune reconstitution, increased relapses with higher doses; but increased risk of acute and chronic GVHD with lower doses.

Methods: We retrospectively evaluated 391 patients undergoing Allo-HSCTs for myeloid malignancies(AML/MDS/MPNs) during 12-year period (Jan 2008 to April 2019) at Kings College Hospital, London. Two dosage schedules of Alemtuzumab based T-cell deplete conditioning with FluBu and Bu-Cy regimens using standard 100mg dose (n-158; 40.4%) were compared to those (n-233; 59.6%) receiving a lower < 100mg dose, with respect to HSCT outcomes. Close monitoring for infections, GVHD, chimerism (included fractionated lymphoid/myeloid) and disease assessments post HSCT were undertaken as per institutional policy.

Results: Baseline characteristics were broadly similar between the 2 groups in terms of conditioning intensity, patient age, underlying disease, disease risk index and donor HLA matching. Median follow up of survivors was 38 months (range 01-136months) with significantly longer follow up available for 100mg group (median 102 months vs 28 months;p< 0.001). Standard Alemtuzumab dose (100mg) was associated with a significant improvement in composite GRFS (54% vs 24% at 60 months; p< 0.001; Fig 1a) and significantly lower incidence of both grade 3-4 acute (18% vs 42% at D100; p-< 0.003; Fig 1b) and chronic GVHD (all grades)(19% vs 42% at 12 months; p< 0.001; Fig 1c) compared to < 100mg dose. No differences in OS (45% vs 45% at 60 months; p-0.55; Fig 1d), NRM (28% vs 23% at 60 months; p-0.32; Fig 1e) and relapse incidences (29% vs 30% at 60 months; p-0.75; Fig 1f) were observed along with no impact on rates of CMV, Adenoviraemia or invasive fungal disease(IFD) between the 2 cohorts, except lower EBV viraemia incidence was noted in 100mg dose group(49% vs 66%; p< 0.001).

Multivariate adjusted cox analysis (MVA) confirmed older age>60 years, mismatched unrelated donor, absence of chronic GVHD, disease relapse, ITU admission event, CMV reactivation and absence of any EBV reactivation post HSCT as significant predictive factors for poor OS, but this not affected by different Alemtuzumab doses, disease risk index or type of disease. Similarly NRM was not affected by differential alemtuzumab doses, while GRFS was positively influenced by standard 100mg dose on MVA

Conclusions: Despite concerns of relapses and delayed immune reconstitution, this report on a homogenous cohort of allo-HSCTs in myeloid malignancies confirms the contrary with no impact on OS, NRM or relapses and no significant increase in opportunistic infections with 100mg dose. With improved supportive care, effective infection management and pre-emptive cellular therapy approaches available in current era, standard dose (100mg) of alemtuzumab can be considered safe and effective in both RIC and myeloablative allo-HSCTs for myeloid malignancies, with significantly lower GVHD related morbidity and overall better GFRS.

Disclosure: No disclosures or conflict of interest to declare.

¹National Institutes of Health, National Cancer Institute, Bethesda, MD, United States, ²National Institutes of Health, National Institute of Allergy and Infectious Disease, Bethesda, MD, United States, ³National Institutes of Health, National Human Genome Research Institute, Bethesda, MD, United States, ⁴Frederick National Laboratory for Cancer Research sponsored by the National Cancer Institute, Frederick, MD, United States

Background: HCT has been used for decades as a definitive therapy in both primary immunodeficiency (PID) and hematological malignancy. A subset of these patients have a dysregulated T cell compartment either due to underlying PID or peripheral T cell lymphoma (PTCL) and are at particularly high risk of graft failure and/or relapse but may also enter HCT with significant comorbidities necessitating a low toxicity approach.

Methods: Twelve patients with PID (n=7) or PTCL (n=5; relapsed, n=3 and primary refractory, n=2), median age 22 years (range 7-64) received a serotherapy-based, radiation-free RIC platform designed with the goals of enhancing host T cell depletion pre-HCT to reduce graft failure risk and provide disease control, while also optimizing immune reconstitution, minimizing toxicities and complications such as graft-versus-host disease (GVHD), and permitting use of alternative donors via a posttransplantation cyclophosphamide-based approach. This was a high-risk cohort with median HCT comorbidity index score of 3 (range 0-7), and active disease in 2 PTCL patients at time of HCT. Alternative donors were commonly used: 5 patients received mismatched grafts (4 haploidentical, 1 mismatched unrelated) and 5 matched unrelated grafts. Patient and donor characteristics are detailed in Figure 1b.

Results: Neutrophil recovery occurred at median day +16 (range 13-25). With median follow up of 6 months (range 2-14), graft-failure-free survival was estimated at 81% at 6 months, with no deaths. There were 2 graft failures (1 primary, in context of rising donor-specific HLA antibodies despite desensitization, and 1 secondary), both now with full donor chimerism after retransplantation. GVHD rates have been low, with grade 1 skin only acute GVHD, not requiring systemic therapy (n=1), grade 2 steroid-responsive acute GVHD of the skin and gut (n=1), and mild chronic GVHD (n=1). Bacterial infectious complications included sepsis/pneumonia (n=2), bacteremia (n=2), and furunculosis (n=1). While BK virus-associated hemorrhagic cystitis occurred at high rates (58%), severe viral complications were infrequent. CMV reactivation occurred in 29% of known at-risk patients (n=2 of 7), with no CMV disease. RSV, asymptomatic adenoviruria, and anemia due to parvovirus B19 occurred in 1 patient each, none requiring inpatient management. At last follow up, some degree of phenotype reversal is evident in all PID patients, and all PTCL patients are either in confirmed complete remission (n=2) or show no clinical signs of disease (n=3).

Conclusions: Based on promising early outcomes, this novel platform offers a safe and effective HCT approach to diseases with historically poor survival or high risk of graft failure, while enabling use of alternative donors. Longer term follow up is needed to better characterize phenotype reversal in PID patients, incidence of relapse in PTCL patients, graft durability, immune reconstitution and late toxicities of the platform.

Clinical Trial Registry: NCT03663933

NCT03922724

Disclosure: None

¹Nantes University Hospital, Nantes, France, ²EFS, Nantes, France

Background: Prophylactic T cell depletion via anti-thymocyte globulin (ATG) during ASCT conditioning is a standard of care for GVHD prophylaxis, although the optimal dosing strategy is still unknown. Recent studies have reported that absolute lymphocyte counts at the time of ATG administration (ALC/ATG) may predict survivals in ASCT with unrelated donors, suggesting that the dose (especially at the cut-off of < 0.1x10⁹/L) and timing of ATG administration must be taken into account (Soiffer et al, JCO 2017; Kennedy et al, BBMT 2018).

Methods: To examine this issue, the outcome of ASCT was evaluated in all consecutive patients transplanted between 2009 and 2019 for a hematologic malignancy in our department. Conditioning regimen were purine analogue/busulfan/ATG-based. The reduced-intensity conditioning (RIC) regimen consisted of fludarabine 30mg/m²/day (d) from d-6 to d-2, busulfan 3,4 mg/kg/d from d-4 to d-3 and ATG (Thymoglobuline, Sanofi, Lyon, France) 2,5 mg/kg/d, d-2 and d-1 (FB2A2) or the same but with clofarabine 30mg/m²/d in replacement of fludarabine with 1 or 2 d of ATG (CloB2A2/CloB2A1). Reduced-toxicity myeloablative conditioning regimens (RTMAC) consisted of the same as FB2A2 but with 3 or 4 d of busulfan instead of 2 (FB3A2/FB4A2). Peripheral blood stem cells were used as source of graft from matched or 9/10 mismatched unrelated donors or siblings. We exhaustively looked at patients for whom a blood differential was available in order to evaluate the impact of lymphocyte counts at the time of ATG administration (ALC/ATG) in terms of overall, disease-free and GVHD-free/relapse-free survival.

Results: Of 395 eligible patients, 116 had a documented differential on the day of ATG administration. The median follow-up for alive patients was 49 months. RIC was administered in 80 (69%) of the patients as follows: 39 FB2A2, 12 CLOB2A2 and 29 CLOB2A1. The 36 other patients received RT-MAC: FB3A2 for 27 and FB4A2 for 9 respectively. Four-year OS, DFS and GRFS were 56.2% (47-66), 40.9% (32-51) and 34.5% (26-45), respectively for the whole cohort.

ROC curve analysis failed to identify a cut-off allowing to predict better survivals according to ALC/ATG. The median ALC/ATG was 0.070x10⁹/L (range: 0-2.300). No difference in terms of survivals was observed when considering patients under this threshold vs others (Fig A). The same was true when considering 0.100x10⁹/L as ALC/ATG cut-off. Regarding MAC, the median ALC/ATG was 0.100x10⁹/L with no difference in survivals between patients under or above this value. The same was true for RIC with ALC/ATG cut-offs below the median (0.055x10⁹/L) or below 0.100 x10⁹/L. Interestingly, considering patients with ALC/ATG below 0.100 x10⁹/L within the RIC setting, survivals were similar between patients who received 1d (n=25) or 2d (n=29) of ATG (Fig B).

Conclusions: This study indicates that ATG can be administered to ASCT recipients whatever the conditioning regimen and the lymphocyte count.

[Survivals according to (A) ALC/ATG (B) number of ATG administration in lymphopenic patients]

Clinical Trial Registry: Non applicable

Disclosure: Nothing to declare.

¹Unifesp, Sao Paulo, Brazil, ²Santa Marcelina, Sao Paulo, Brazil, ³INCOR, Sao Paulo, Brazil, ⁴USP, Sao Paulo, Brazil

Background: Myeloablative conditioning regimens for HSCT elicits high toxicity

Maranhao (1994, 2003) have already showed that lipid core nanoparticles (LDE), as carrier of anti-cancer drugs reduces drug toxicity. We tested LDE-etoposide in the myeloablative conditioning regimen of HSCT of AML patients not responding to induction therapy.

Methods: A prospective pilot study with 15 patients from 2 academic hospitals in São Paulo, Brazil

Inclusion criteria: primary AML not responding to the induction therapy, 18 - 70yr, HLA-matched related or unrelated donor, ECOG ≤ 2, Karnofsky ≥ 80, and comorbidity score ≤ 2. Exclusion criteria: haploidentical donor or umbilical cord blood.

Conditioning regimen: LDE-etoposide from 20mg/kg/BW until 60mg/kg/BW on D-7 and D- 6 and TBI 1200cGy on D-3, D-2 and D-1. D0: day of stem cells infusion. For unrelated donors, thymoglobulin was added. Graft-vs-host disease (GVHD) prophylaxis: cyclosporine and methotrexate.

Results: 15 AML patients (8 males, 7 females), aged 22-66 yrs (median 47 yrs), 10 x 10 HLA-matched stem cells (9 related, 6 unrelated donors) were enrolled. Peripheral stem cell donors were mobilized with GCSF. CD34+ average infused cells were 7.6±1.6 x 10⁶ /kg/BW. Two patients received peripheral and marrow stem cells: CD34+ (9.0±1.0 x 10⁶ cells/kg/BW) and TNC (3.5±0.5 x 10⁸ cells/kg/ BW). Neutrophil engraftment occurred on day 20 ± 5 and platelet 16 ± 4. All patients engrafted. There were no episodes of hypotension, anaphylaxis, or other adverse effects during LDE-etoposide infusion. There was no grade 4 or higher toxicities. Grade 3 toxicity: mucositis (6 patients), diarrhea (3) and elevation of total bilirubin (1), all before D+30. SOS was observed in 1 patient based on the Seattle criteria, which did not fulfill the Baltimore criteria.

Acute GVHD: skin grade 1 in 4 patients and grade 2 in 1. One patient had skin and GI grade 1 aGVHD. The rate of systemic aGVHD was 33,7% (26.7% grade 1, 6.7% grade 2). Chronic GVHD: 8 patients (57,1%): 4 moderate global cGVHD (28.6%) and 4 severe global cGVHD (28.6%). No fatal GVHD events occurred.

CMV reactivation: 5 patients before D+100 and 1 patient after D+100. Bacterial infection: 7 patients before D+ 100 (3 by multiresistant bacteria) and in 7 patients after D+100 (2 by multiresistant bacteria). One patient had disruption of the pulmonary aspergilloma on D+41 after engraftment and one reactivated Aspergilosis sp infection after D+60.

Five patients died, one before D+100 (aspegilloma disruption), 3 patients of refractory relapse on D+174; D+207, and D+285; and 1 patient during re-induction therapy on D+181. Seven patients are in complete response with 100% chimerism.

The median follow-up time of patients was 17.4 months (41 - 836days). Cumulative incidences of overall survival, event-free survival, relapse and non-relapse mortality at 27 months were 66.7%, 46.7%, 46.7% and 6.7% respectively.

Conclusions: LDE-etoposide based conditioning regimen of HSCT for AML has a clear-cut potential for being advantageously introduced in the clinical practice.

Disclosure: Nothing to declare.

¹Universität Köln, Köln, Germany, ²Universitätsklinikum Großhadern, Ludwig-Maximilians-Universität, München, Germany

Background: Conditioning regimens and the choice of immunosuppression have substantial impact on immune reconstitution after allogeneic hematopoietic stem cell transplantation (aHSCT). The pivotal mechanism to achieve and maintain remission in patients undergoing allogeneic transplantation is the induction of the graft-versus-tumor effect (GvT). Such GvT effects are not achieved in all patients transplanted and relapse is a common event. Moreover, graft versus host disease (GvHD) attacking the recipients’ healthy tissues often preceeds the development of the GvT effect and requires prolonged immunosuppressive therapy hereby abolishing the desired GvT effect. Classic immunosuppressive strategies implementing calcineurin inhibitors (CNI) hamper the immune recovery and built-up of the anti-cancer immune response.

Methods: We designed a phase II clinical study for patients with high-risk hematological malignancies using a CNI-free approach consisting of post-transplant cyclophosphamide and short-term everolimus, an immunosuppressant with anti-proliferative properties given from d+5 to d+100, after reduced-intensity conditioning and matched peripheral blood stem cell transplantation. Results after recruitment of all 19 patients planned will be presented.

Results: Nineteen patients with relapsed or refractory lymphoma and myeloma at high-risk for relapse underwent allogeneic peripheral blood stem cell transplantation with a matched related or unrelated donor after conditioning with fludarabine and busulfan. After application of post-transplant cyclophosphamide on d+3 and +4 after transplant, short-term everolimus was given from d+5 to d+100. Primary endpoint is the cumulative incidence and severity of acute GvHD. All patients presented a complete donor chimerism by d+30 and d+100. Engraftment was delayed with 17, 29 and 27 days for neutrophils, hemoglobin and platelets, respectively. The overall incidence of acute GvHD was 53%. Grade II aGvHD was found in 36% while none of the patients experienced grade III or IV aGvHD. In most cases aGvHD presented as cutaneous manifestation shortly after engraftment. The overall incidence of chronic GvHD was 21%, which was mild in all cases. Two patients died due to sepsis 18 and 20 days after transplant. One patient died due to secondary AML/ MDS three years after transplant. The cumulative incidence of non-relapse mortality on d+100 and d+365 was 11% with a median follow-up of 628 days (18-1152 days). There was one secondary graft failure. The cumulative incidence of relapse was 32% and 37% at one and two years after transplant, respectively. Relapse-free survival was 58% and 52% after one and two years. The overall survival was 73% and 64% after one and two years. All surviving patients are currently without cGvHD and immunsuppressive medication.

Conclusions: The use of post-transplant cyclophosphamide and short-term everolimus is safe with low rates of aGvHD, no severe aGvHD and a low incidence of mild cGvHD translating into a low rate of early non-relapse mortality. The relapse rates in this difficult to treat patient population are encouraging and warrant further studies using the combination of post-transplant cyclophosphamide and everolimus.

Clinical Trial Registry: Study protocol code: Uni-Koeln-1717 EudraCT number: 2013-005507-14

Disclosure: The study was supported by a research grant from Novartis to CS/UH. The other authors have no conflicts of interest to disclose.

¹IRCCS San Raffaele Scientific Institute, Milan, Italy, ²University Vita-Salute San Raffaele, Milan, Italy

Background: Allogeneic hematopoietic stem cell transplantation (allo-SCT) remains the only potentially curative treatment for many hematological malignancies. For most of these, median age of occurrence is 60 years and even more. Nevertheless, the use of allo-SCT had been usually limited to a younger population because of concern related to non-relapse mortality (NRM) of older patients. We here report our large experience in allo-HSCT in patients diagnosed with hematological malignancies and older than 64 yrs.

Methods: From 2005 to 2019, 118pts older than 64yrs received a T-replete allo-SCT for acute leukemias (88pts, 75%), myelodysplastic syndromes (21pts, 18%) or others hematological malignancies (9pts, 7%) at our center. Donors were matched siblings in 19pts (16%), unrelated in 39pts (33%), haploidentical in 57pts (48%) and single cord blood unit in 3pts (3%). Median age at transplant was 67y (65-76). Seventy-seven patients (65%) were transplanted in early disease status (complete remission, CR, or upfront) while 41pts in active disease (35%). One-hundred and six patients out of 118 (90%) received a myeloablative treosulfan-fludarabine based conditioning regimen. Graft-versus-host-disease prophylaxis was sirolimus-based in 91 out of 118 pts (77%), cyclosporine-based in 27pts (23%). Post-transplant Cyclophosphamide was used in 68pts (58%), antithymocyte globulin in 41pts (35%).

Results: Median follow-up among survivors (63pts) was 35 months (3-104). All but two patients engrafted. Median time from transplant to engraftment was 21 days for neutrophils (11-50) and 24 days for platelets (9-632).

Overall survival (OS) at 1 and 3 years was 67+/-4% and 56+/-5%, respectively. Disease free survival (DFS) at 1 and 3 years was 62+/-5% and 46+/-5%, respectively. Day-100 NRM was 18+/-4%. The 1 and 3-year NRM was 26+/-4% and 36+/-5%, respectively. The 1 and 3-year cumulative incidence (CI) of relapse was 16+/-4% and 27+/-5%. Day-100 CI of acute GvHD grade II-IV was 41+/-5%, of grade III-IV was 15+/-3%. CI of overall cGvHD at 1 year was 30+/-5%, of extensive cGvHD was 19+/-4%. No differences in transplant outcomes were found in patients younger or older than 70yrs.

In multivariate analysis early disease status at transplant was the only risk factor associated to OS (HR 0.478; p=0.007. CI: 0.279-0.818), DFS (HR 0.435; p=0.001. CI: 0.262-0.722) and NRM (HR 0.433; p=0.011. CI: 0.227-0.823). The 3-year OS, DFS and NRM for patients transplanted in early disease status were as follows: 70+/-5%, 58+/-6% and 13+/-4%, respectively. Matched sibling donors were associated to lower CI of day-100 aGvHD in multivariate analysis (HR 0.538; p=0.023. CI: 0.316-0.918). Diagnosis of acute leukemia was the only risk factor associated to lower CI of cGvHD (HR 0.311; p=0.00044. CI: 0.162-0.597).

Conclusions: Based on our results we can conclude that age alone should not limit allo-SCT eligibility of patients with hematological malignancies, above all in early disease status. The use in the majority of our patients of treosulfan, an alkylating agent with a low toxic profile, could have contributed to the low incidence of NRM without negatively affecting long-term disease control.

Disclosure: Nothing to declare.

¹H Lee Moffitt Cancer Center and Research Institution, Tampa, FL, United States, ²University of South Florida, Tampa, FL, United States, ³Memorial Healthcare System, Pembroke Pines, FL, United States

Background: A recent large CIBMTR study demonstrated no survival benefit with use of myeloablative (MAC) compared to reduced-intensity conditioning (RIC) in patients receiving allogeneic hematopoietic cell transplant (alloHCT) for acute myeloid leukemia (AML) or myelodysplastic syndrome with high-risk disease risk index (DRI) (Bejanyan, ASH 2019). While commonly used MAC fludarabine-busulfan (FluBu) and RIC fludarabine-melphalan (FluMel) result in similar outcomes after alloHCT for AML in remission (Eapen, Blood Adv 2018), the preferred conditioning regimen for active or detectable residual (MRD+) AML at alloHCT remains unknown.

Methods: We analyzed outcomes of 125 patients with active (n=62) or MRD+ (n=63) AML who received alloHCT (2005-2017) with either MAC FluBu4 (72%) with PK-targeted IV daily average Bu AUC of 5300 or RIC FluMel (28%) with total Mel dose of 140 mg/m2.

Results: The group receiving FluMel had a higher proportion of >60-year-old patients (74% vs 21%, p< 0.001), adverse genetic risk AML by ELN 2017 (63 % vs. 51%, p=0.015), alloHCT performed from 2015-2017 (83% vs. 33%, p< 0.001) and Tacrolimus/ Sirolimus-based GVHD prophylaxis (86% vs. 50%, p=0.001). The rest of the characteristics were similar between FluBu and FluMel recipients, including the disease status at HCT (active AML, 54% vs. 37%, p=0.14). Probabilities of 2-year non-relapse mortality (NRM), relapse, leukemia-free survival (LFS) and overall survival (OS) are shown in the Figure. In multiple regression analysis after adjusting for disease status at alloHCT (active vs. MRD+) and DRI, the FluMel regimen compared to FluBu resulted in significantly lower risk of relapse (HR=0.26, 95% CI 0.11-0.63; p=0.003) and higher LFS (HR=0.49, 95% CI 0.28-0.86; p=0.014), but there was only a statistically non-significant trend of better OS (HR=0.57, 95% CI 0.32-1.02; p=0.06) (Table). NRM was similar between the two conditioning groups.

Conclusions: In conclusion, our data support the use of the RIC FluMel regimen for alloHCT in patients with MRD+ or active AML as it results in lower risk of relapse and better LFS compared to MAC FluBu. This study´s findings require confirmation in a larger cohort of patients with MRD+ and active AML.

[Multivariate Analysis of Clinical Outcomes]

[Clinical outcomes of active or MRD+ AML patients by conditioning regimen]

Disclosure: Aleksandr Lazaryan- Eusa Pharma LLC scientific advisory board

The rest of the authors have nothing to declare.

Ulm University Medical Center, Ulm, Germany

Background: Reduced Intensity Conditioning (RIC) regimens allowed allogeneic stem cell transplantation (allo-SCT) for patients with high risk hematological malignancies at advanced age and/or with comorbidities. In aggressive leukemia, RIC regimens may not be sufficient to control the disease, resulting in high relapse rates. The FLAMSA RIC regimen, that associates a short course of chemotherapy with a RIC backbone including TBI 4Gy, reported encouraging results in the treatment of high risk AML and MDS. Still the original protocol is associated with acute toxicity, mainly due to TBI. In this context Treosulfan is being investigated at different dosages as an attractive alternative in order to ameliorate the toxicity profile, preserving the anti-leukemic activity in a high risk population.

Methods: We substituted in the FLAMSA protocol (Schmid, JCO 2005) the TBI with Treosulfan 12g/m2/d from day -6 to -4 (FLAMSA-Treo). A retrospective comparison was then performed between FLAMSA-TBI and FLAMSA-Treo considering patients with high risk AML in first Complete Remission (CR1) and high-risk MDS. The high risk status was defined according to molecular markers, karyotype, delayed response to induction chemotherapy, and AML secondary to MDS or previous chemotherapy. Standard risk AML patients in molecular relapse after standard treatment were also considered “high risk”. The decision to treat patients with FLAMSA-Treo instead of FLAMSA-TBI conditioning was at the physician’s board discretion according to TBI availability, patient age and/or presence of comorbidities.

Results: Between 01/2006 and 06/2019 a total of 59 patients with high risk AML in CR1 (n=53) and high risk MDS (n=6) received allo-SCT after a FLAMSA conditioning. Out of 59 patients, in 45 (76%) a FLAMSA-TBI protocol was administered, while in the remaining 14 (24%) Treosulfan replaced TBI. All the patients, except three, received PBSC as source of transplantation. The GvHD Prophylaxis was based on a combination between CyclosporinA and Mycophenolate Mofetil. Further Patients’ characteristics are listed in Figure 1a. Comparing the outcome of the two subpopulations (TBI vs Treo), no significant differences were observed in terms of OS (1yOS 73% vs 90% respectively, p=0.15), TRM (1yTRM, 45% vs 7%, p=0.3) and relapse incidence (1yRI 22% vs 20%, p=0.4). Considering that we introduced the FLAMSA-Treo platform mostly in the last two years (13/14 pts) and in order to minimize potential biases related to the year of transplantation, we performed a time driven sub-analysis, including only patients transplanted since 01/2017 in both cohorts (n=23, TBI n=10, Treo n=13). In this context, Treosulfan proved to confer a survival advantage to TBI-based conditioning (1yOS 92% vs 50%, p=0.05), manly due to a reduction in the transplant related mortality (1yTRM 8% vs 40%, p=0.09).

Conclusions: In our analysis the Treosulfan-based FLAMSA protocol demonstrated a favorable toxicity profile, at least not inferior to the standard platform including TBI, for the treatment of high risk AML/MDS older patients and/or with comorbidities. The reduced toxicity profile of Treosulfan could favor especially AML patients in first complete remission. A larger prospective series of patients is needed in order to confirm these promising preliminary findings.

Disclosure: Sala E: Honoraria with Gilead.

¹Tokyo Women’s Medical University, Tokyo, Japan, ²Imamura General Hospital, Kagoshima, Japan, ³Chiba University Hospital, Chiba, Japan, ⁴Federation of National Public Service Personnel Mutual Aid Associations, Toranomon Hospital, Tokyo, Japan, ⁵Osaka University Hospital, Osaka, Japan, ⁶Shinshu University, Nagano, Japan, ⁷Kindai University Hospital, Osaka, Japan, ⁸Jichi Medical University Saitama Medical Center, Saitama, Japan, ⁹National Cancer Center Hospital, Tokyo, Japan, ¹⁰Japanese Data Center for Hematopoietic Cell Transplantation, Aichi, Japan, ¹¹Nagoya University, Aichi, Japan

Background: Fludarabine and a myeloablative dose of intravenous busulfan (Flu/Bu4) are widely used together in allogeneic hematopoietic stem cell transplantation (alloHSCT) as a reduced-toxicity conditioning regimen. Although Flu/Bu4 has been applied to a wide range of age groups, the increasing number of transplant-related complications observed among elderly patients remains a major concern.

Methods: We conducted a retrospective survey of alloHSCT in Japan, using the transplant outcomes registry database maintained by the Transplant Registry Unified Management Program. The following inclusion criteria were applied: patients >15 years old with hematological malignancies who had received their first alloHSCT between 2006 and 2017, and who were treated with Flu/Bu4 (total intravenous busulfan dose of 11.2-16 mg/kg or equivalent). Patients who received total body irradiation (TBI) or other chemotherapeutic drugs were also included. Patients who received alloHSCT from cord-blood donors were excluded.

Results: The median age of patients was 58 years (range 16-80), and 43.4% of patients were 60 years or older. Of 1,443 patients, 62.6% were male. Patients were diagnosed with myeloid malignancies (87.1%), lymphoid malignancies (9.1%), and other malignancies (3.0%). Approximately two-third of the patients (66.4%) received bone marrow transplantation, and 584 (25.5%) and 830 (36.3%) patients received alloHSCT from matched related donors and 8/8 matched unrelated donors. The 5-year overall survival (OS) rate after alloHSCT was 45.5% (95% confidence interval [CI]: 42.3.5%-48.6%) for the young group (< 60 years) and 34.8% (95% CI: 31.2%-38.5%) for the elderly group (≥60 years). Although the 5-year cumulative incidence of relapse was equivalent between the two groups (P = 0.67, 32.7% and 33.8%, respectively), the 5-year non-relapse mortality (NRM) was significantly higher for the elderly group (34.0%) than for the young group (25.0%) (P < 0.01). According to the multivariate analysis, increased patient age (≥60 years) was associated with an increased risk of poor OS (hazard ratio [HR] 1.33, 95% CI: 1.19-1.49, P < 0.01) and poor NRM (HR 1.40, 95% CI: 1.19-1.65, P < 0.01). In the subgroup analysis of the elderly group, advanced diseases, administration of chemotherapeutic drugs in addition to Flu/Bu4, and poor performance status (>0) were significant risk factors for poor OS. Those patients who received chemotherapeutic drugs in addition to Flu/Bu4 experienced thrombotic microangiopathy and bleeding complications more frequently than those who did not (P < 0.01 for both comparisons); however, no significant differences were observed for primary causes of death. Nearly half of the elderly patients received TBI with Flu/Bu4. No significant difference in the OS was observed between patients treated with and without TBI; however, TBI resulted in significantly increased NRM (P < 0.01). Elderly patients treated with TBI experienced sinusoidal obstruction syndrome (P < 0.01) and bleeding complications (P = 0.04) more frequently than those treated without TBI.

Conclusions: Flu/Bu4 for elderly patients was associated with increased NRM, resulting in poor OS. In particular, the administration of additional chemotherapeutic drugs or TBI in combination with Flu/Bu4 in elderly patients increased the incidence of certain complications, which might be associated with poor NRM. Therefore, Flu/Bu4 should be used with caution in elderly patients.

Clinical Trial Registry: Not applicable

Disclosure: The authors declare. no conflict of interest. This work was supported in part by the Practical Research Project for Allergic Diseases and Immunology (Research Technology of Medical Transplantation) from Japan Agency for Medical Research and Development, AMED.

City of Hope, Duarte, CA, United States

Background: Total marrow and lymphoid irradiation (TMLI) delivers augmented doses of radiation to the bone marrow while maintaining low doses to vital organs. We have conducted a phase II study in which we combined TMLI with cyclophosphamide (Cy) and etoposide (VP16) as a conditioning regimen to evaluate its anti-leukemia activity and safety/tolerability in patients with relapsed/refractory acute leukemia. We report here on 57 patients with a median of more than one year of follow-up.

Methods: TMLI (2000cGy to targets, 1200cGy to liver/brain) was administered on days -9 to -5, VP16 60mg/kg (adjusted body weight) on day -4, and Cy 100mg/kg (ideal body weight) on day -2. Bone marrow (n=6) or peripheral blood stem cells (n=51) were given on day 0. Graft versus host disease (GVHD) prophylaxis used was tacrolimus and sirolimus. The primary endpoint was progression free survival (PFS), and secondary endpoints included overall survival (OS), non-relapse mortality (NRM), and toxicity.

Results: Of the 57 patients (Table) with a median of at least 1 year of follow up, the median follow up was 12.5 months (range 1.1-48.3). Engraftment was noted for all patients. The CR/CRi rate at day +30 was 100% for the 56 patients with available data. Disease relapse/progression at 1 year was 47% (95%CI: 35-62). The estimates of NRM at 100 days and 1 year were 4% (95%CI: 1-14) and 6% (95%CI: 2-17), respectively. Relapsed disease after transplant occurred in 34 patients (60%). Four patients died in remission because of infections (n=2), West Nile encephalitis, and cGVHD.

One-year estimates of OS and PFS were 67% (95%CI: 53-78) and 48% (95%CI: 34-60), respectively. The OS/PFS of patients with a Duval score of ≥2 (i.e., high risk) was not statistically significantly different than those associated with a score < 2.

Grade ≥2 Bearman toxicities were bladder (Gr2 n=2), central nervous system (Gr2 n=1), gastrointestinal (Gr2 n=4), hepatic (Gr2 n=1, Gr3 n=1), pulmonary (Gr2 n=1), and renal (Gr2 n=2, Gr3 n=2). Grade 2 and 3 stomatitis occurred in 12 and 2 patients, respectively. There were no grade 4 toxicities or toxicity-related deaths. Acute GVHD was manageable and consistent with previous experience with the regimen.

Conclusions: 1) TMLI can be safely delivered in combination with VP16 and Cy, with NRM rates < 10%; 2) The regimen is effective for patients with relapsed/refractory acute leukemia; 3) Patient outcomes are superior over traditional rates as reported by Duval et al (Duval et al., J Clin Oncol 2010, pp.3730-9).

[Patient characteristics. *28 patients had 0% and were excluded. **5 patients had extramedullary disease.]

Clinical Trial Registry: NCT02094794

Disclosure: Anthony Stein: Stemline: Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau.

Joycelynne Palmer: Gilead Sciences: Consultancy.

Haris Ali: Incyte: Consultancy, Speakers Bureau.

Ibrahim Aldoss: Jazz Pharmaceuticals: Honoraria, Other: travel/accommodation/expenses, Speakers Bureau; Agios: Consultancy, Honoraria; Helocyte: Consultancy, Honoraria, Other: travel/accommodation/expenses; AUTO1: Consultancy.

Ryotaro Nakamura: Kirin Kyowa: Other: support for an academic seminar in a university in Japan; Merck: Membership on an entity´s Board of Directors or advisory committees; Celgene: Other: support for an academic seminar in a university in Japan; Alexion: Other: support to a lecture at a Japan Society of Transfusion/Cellular Therapy meeting

Amandeep Salhotra: Celgene: Other: Research Support; Kadmon Corporation: Other: Non paid consultant. Ali: Incyte: Consultancy, Speakers Bureau.

¹Magenta Therapeutics, Cambridge, MA, United States, ²University of Minnesota, Minneapolis, MN, United States, ³Fred Hutchinson Cancer Research Center, Seattle, WA, United States

Background: Allogeneic hematopoietic stem cell transplant (Allo-HSCT) is a potentially curative treatment for malignant and non-malignant blood disorders. However, current conditioning regimens limit the use of this curative procedure due to conditioning-related mortality and morbidities. As a result, many patients are not able do not undergo this potentially curative therapy. We developed a novel antibody drug conjugate (ADCs) to provide a readily translatable approach that is fully myeloablative as a single agent while reducing the toxicity associated with current conditioning agents. We have generated an anti-mouse CD45 ADC to model this approach for conditioning recipients for minor mismatch and fully allogeneic HSCT.

Methods: Our tool CD45 ADC is engineered for rapid clearance (T1/2=1.7hr) to enable HSCT after conditioning, and a single dose of 3 mg/kg is fully myeloablative. To determine if the tool CD45-ADC could successfully condition recipients for minor histocompatibility antigen mismatched allo-HSCT, we used a single dose of the tool CD45-ADC to condition DBA/2 hosts (H-2d, CD45.2+) for transplant with CByJ.SJL(B6) mice (H-2d, CD45.1+). A matched dose of non-targeted isotype ADC (Iso-ADC) was used as a negative control, while 9 Gy TBI was used as the conventional conditioning positive control. To determine if the tool CD45 CD45-ADC could successfully condition recipients for fully mismatched allo-HSCT, we compared the ability of a single dose of the tool CD45-ADC, alone or supplemented with various levels of TBI, to condition C57BL/6 hosts (H-2b, CD45.2+) for transplant with cells from CByJ.SJL(B6) mice. We used matched doses of Iso-ADC with and without supplemental TBI and 9 Gy TBI as controls. In both studies, conditioned mice were transplanted with 2x107 whole BM cells, and peripheral chimerism was monitored over 16 weeks.

Results: In the minor mismatch (Balb/c CD45.1+→DBA/2 CD45.2+) model of allogeneic HSCT, a single dose of the tool CD45-ADC enabled full donor chimerism through 12 weeks as a single agent (Figure 1A); >90% donor chimerism was observed in T-, B-, and myeloid lineages, comparable to 9 Gy TBI conditioning. Treatment with a matched dose Iso-ADC was not effective. In the fully mismatched Balb/c → C57Bl/6 allo-HSCT model, CD45-ADC as a single agent enabled partial, transient chimerism at 3 weeks post-transplant; an iso-ADC did not. With CD45-ADC as the primary agent, supplementation with TBI doses as low as 0.5 Gy enabled durable full donor chimerism (Figure 1B), comparable to 9 Gy TBI alone. Iso-ADC required a minimum supplementation of 4 Gy TBI to enable donor chimerism.

Conclusions: Conditioning with CD45-ADC is fully myeloablative and enables complete chimerism in a minor mismatch allo-HSCT model as a single agent and enables complete chimerism in the full mismatch allo-HSCT model when supplemented with low dose (0.5 Gy) TBI. This targeted, readily translatable approach for safer conditioning could improve the risk-benefit profile for allogenic and haploidentical HSCT and may extend the curative potential of HSCT to more patients suffering from blood cancers and other diseases that may benefit from HSCT.

[Figure 1]

Disclosure: Sharon Hyzy- Ownership Interest and Salary, Magenta Therapeutics

Rahul Palchaudhuri- Ownership Interest and Salary, Magenta Therapeutics

Jennifer Proctor- Ownership Interest and Salary, Magenta Therapeutics

Bradley Pearse- Ownership Interest and Salary, Magenta Therapeutics

Ganapathy Sarma- Ownership Interest and Salary, Magenta Therapeutics

Geoff Gillard- Ownership Interest and Salary, Magenta Therapeutics

Asim Saha- Nothing to declare.

Tahirih Lamothe- Ownership Interest and Salary, Magenta Therapeutics

Melissa Brooks- Ownership Interest and Salary, Magenta Therapeutics

Katelyn Hammond- Ownership Interest and Salary, Magenta Therapeutics

Anjali Bhat- Ownership Interest and Salary, Magenta Therapeutics

Nicholas Clark- Ownership Interest and Salary, Magenta Therapeutics

Charlotte McDonagh-- Ownership Interest and Salary, Magenta Therapeutics

Hans-Peter Kiem- Nothing to declare.

John Wagner- Consultant, PI (Magenta Therapeutics); Board Member (Gadeta); PI (BlueRock); Consultant (Rocket Pharma); PI (Novartis)

Bruce Blazar- Advisory Board Member (Kamon Pharmaceuticals, Five Prime Therapeutics, Regeneron Pharmaceuticals, Magenta Therapeutics, BlueRock Therapeutics); Research support (Fate Therapeutics, RXi Pharmaceuticals, Alpine Immune Sciences, Abbvie, BlueRock Therapeutics, Leukemia and Lymphoma Society, Childrens´ Cancer Research Fund, KidsFirst Fund); Co-Founder (Tmunity)

Anthony Boitano- Ownership Interest, Royalty and Salary (Magenta Therapeutics)

Michael Cooke- Ownership Interest and Salary (Magenta Therapeutics)

¹Helios Klinikum Erfurt, Erfurt, Germany, ²Universitätsklinik Heidelberg, Heidelberg, Germany, ³Klinikum Essen Süd, Essen-Werden, Germany, ⁴Universitätsmedizin Berlin, Berlin, Germany, ⁵Universitätsklinikum Jena, Jena, Germany, ⁶Universitätsklinikum Leipzig, Leipzig, Germany, ⁷Klinikum Stuttgart, Stuttgart, Germany, ⁸Helios Klinikum Duisburg, Duisburg, Germany, ⁹Klinikum Oldenburg, Oldenburg, Germany, ¹⁰Evangelisches Krankenhaus Bielefeld, Bielefeld, Germany, ¹¹Malteser Krankenhaus Flensburg, Flensburg, Germany, ¹²Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany, ¹³Städtisches Klinikum Karlsruhe, Karlsruhe, Germany, ¹⁴Universitätsklinikum Essen-Duisburg, Essen, Germany, ¹⁵Diakonissen-Klinik Schwäbisch-Hall, Schwäbisch-Hall, Germany

Background: Thiotepa-containing high-dose chemotherapy (HDCT) followed by ASCT is considered as standard of care in the treatment of primary or secondary central nervous system lymphoma (PCNSL/SCNSL) based on its capacity to penetrate the blood-brain barrier. In order to collect data in daily practice, this prospective, multicenter, non-interventional study was initiated to evaluate thiotepa-based HDCT prior to ASCT in patients with PCNSL or SCNSL, or non-CNS lymphoma: non-Hodgkin or Hodgkin lymphoma (NHL, HL). Primary aims of this study were assessment of safety and efficacy of thiotepa-based high-dose regimens in ASCT for lymphoma.

Methods: Eligible patients were 18 years of age or older and were assigned to undergo ASCT after HDCT either with thiotepa 20 mg/kg, BCNU 400 mg/m² +/- etoposide 450 mg/m² (TT+BCNU) for PCNSL/SCNSL; or thiotepa 10 mg/kg, etoposide 800 mg/m², araC 1600 mg/m², melphalan 140 mg/m² (TEAM) for non-CNS lymphoma (B-/T-NHL, HL). Primary endpoints were toxicity and efficacy. Data were documented at 4 time-points: before therapy, at day 30, day 100 and 1 year post ASCT.

Results: From Oct 2013 to Apr 2017, 83 patients were registered by 16 centers, of whom 80 [51 male,] had a complete dataset available and were included in this analysis. Median age was 59 years (range: 22-78), with 12 patients being older than 65 years. T+BCNU and TEAM were used in 44 (55%) and 33 (41%) patients, respectively, and other combinations in the 3 remaining patients. Diagnosis was PCNSL in 32 (40%) patients, SCNSL in 13 (16%) patients, and NHL/HL) without CNS involvement in 35 (44%) patients. Main non-hematological grade 3-4 organ toxicities up to day +30 were mucositis, diarrhea, infection, and fever, occurring in 67%, 21%, 47%, and 16%, respectively, of all 80 patients. Neutrophil recovery (>500/µl) occurred at a median of 10 days (4-21), and platelet recovery (>20.000/µl) at a median of 13 days after transplantation. Non-relapse mortality at day +100 and 1 year was 8.8% corresponding to non-adjusted 7 fatalities, all infection related with no impact of underlying disease, thiotepa regimen used, and age. On day 100, 72 patients were evaluable for response, here 42 (53%) achieved complete response, 20 (25%) partial response and 3 (4%) patients stable disease. Nineteen (24%) patients experienced relapse/progression, translating into a progression-free survival at one year of 68% (PCNSL: 78%; SCNSL: 54%; B-/T-NHL, HL: 63%), and an overall survival of 78% (PCNSL: 81%; SCNSL: 69% and B-/T-NHL, HL: 77%). No difference of therapy outcome could be detected in patients being < or > 60 years, but a worse PFS and OS for patients older than 65 years.

Conclusions: The results of this prospective study suggest that thiotepa-based high-dose chemotherapy for ASCT for both CNS and non-CNS lymphoma is effective and does not raise safety concerns compared to other HDCT regimens commonly used for ASCT of lymphoma across all age groups.

Clinical Trial Registry: CTU82G

Disclosure: Herbert G. Sayer: Honoria from RIEMSER Pharma GmbH

¹Universitá Cattolica del Sacro Cuore, Roma, Italy, ²Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy

Background: GvHD remain a significant complication in HLA matched grafts, receiving prophylaxis with cyclosporin (CSA), methotrexate (MTX), also when combined with anti-thymocyte globulin (ATG). In a prospective study the triple combination of post-transplant cyclophosphamide (PT-CY), CSA and mycophenolate (MMF), has shown to provide the best protection against GvHD in HLA matched transplants (Bolanos, Lancet Haematol, 2019)

Methods: To assess the outcome of HLA matched grafts receiving GvHD prophylaxis with PTCY+CSA+MMF or ATG+CSA+MTX, we retrospectively analyzed the outcome of 113 HLA identical transplants grafted from identical siblings (SIBS) (n=58) or 8/8 allelic matched unrelated donors (MUD) (n=55). GvHD prophylaxis was PTCY based in 28 and ATG based in 85.

The median age was borderline lower in the PTCY arm (48 vs 53 years, p=0.08). The conditioning regimen for 82% of patients in both arms, was thiotepa (10 mg/kg), busulfan 9.6 mg/kg and fludarabine 150 mg/m^2 (TBF); full dose TBI (12 Gy) was given to 4% of the ATG based patients and 14% of the PTCY based patients (p=ns). The disease phase was equally distributed in the two groups. Acute leukemia was the most frequent diagnosis in 48% and 46% of patients respectively, followed by MDS in 19% and 16% and myelofibrosis in 14% and 17%. Peripheral blood was the graft source for all patients.

Results: Median time to neutrophils 0.5x10^9/l was day 16 vs 18 days in the ATG vs PTCY patients (p=0.01). The proportion of patients with grade 0 acute GvHD was 25% for ATG and 94% for PTCY (p=0.00001); GvHD grade II developed in 19% vs 5% respectively an grade III-IV in 2% vs 0% (p=0.002). Chronic GvHD was absent in 54% vs 96% of ATG vs PTCY patients, and moderate severe cGvHD was diagnosed in 27% vs 0% (p=0.0008). TRM was documented in 22% vs 7% of ATG vs PTCY patients (p=0.07). Follow up is too short to analyzed relapse and survival. We compared matched grafts receiving the triple PTCY based GvHD prophylaxis, with a large concurrent group of HAPLO mismatched family grafts receiving the same prophylaxis (n=105): the incidence of GvHD grade II-IV was 21% in the HAPLO grafts and 3% in the matched grafts (p=0.01), given the same GvHD prophylaxis. Similarly cGvHD (moderate severe) was diagnosed in 19% of HAPLO grafts vs 0% of matched grafts (p=0.0009).

Conclusions: Data suggest that for HLA matched transplants, a triple PTCY based -GvHD prophylaxis is significantly superior to a triple ATG based -GvHD prophylaxis, in protecting patients from acute and chronic GvHD and results in a low TRM. It also suggests that, given the same PTCY based prophylaxis, GvHD is less frequent in matched related and unrelated grafts as compared to HAPLO mismatched grafts, reassessing the role of HLA matching in allogeneic transplants. We need to determine whether relapse is not increased given the extremely low incidence of GvHD, with the triple PTCY based GvHD prophylaxis in matched grafts. However, if these results can be reproduced, we may find out that HLA matching returns as a major predictor of GvHD.

Disclosure: No disclosures

Memorial Sloan Kettering Cancer Center, New York, NY, United States

Background: Allogeneic hematopoietic cell transplantation (allo-HCT) allows for the possibility of cure for patients (pts) with non-Hodgkin Lymphoma (NHL) as it provides an immunologic graft-versus-lymphoma effect. Non-relapse mortality (NRM) was felt to be prohibitive with myeloablative regimens, but technical advances with the advent of reduced-intensity conditioning (RIC) or nonmyeloablative (NMA) regimens have decreased these rates. RIC regimens are generally associated with more toxicity and higher NRM than NMA regimens. Though studies showed both approaches are safe and effective, there is lack of direct comparison between these different intensities of in NHL.

Methods: This retrospective study identified patients aged ≥ 18 years who underwent allo-HCT for relapsed/refractory NHL between 3/2008-6/2017 at our center. Outcomes were compared between pts who received NMA and RIC conditioning, with intensity delineated per CIBMTR definitions. Progression-free survival (PFS) was the primary outcome. Secondary outcomes included overall survival (OS) and non-relapse mortality (NRM). Additional outcomes included rates of acute GVHD at Day 100, chronic GVHD, and CMV reactivation at Day 100. Regimen intensity and other variables significant by univariate analysis were included in the multivariate analysis.

Results: For the 144 patients identified, the median age was 56 years (range, 19-79). More pts received NMA regimens (n=80, 56%) and most did not undergo prior autologous HCT (n=103, 72%). NMA regimens were given more frequently to pts with indolent B-cell lymphoma and were more likely to receive ATG and/or rituximab (p = 0.008, p < 0.001, and p < 0.001, respectively). At a median overall follow-up of 57.8 months (range 49 - 75.1) neither median PFS or OS were reached. In univariate analysis, NMA conditioning was associated with a longer PFS than RIC [HR 1.9 (1.11-3.24), p = 0.019). No difference in OS when comparing NMA and RIC regimens [HR 1.56 (0.85-2.85), p = 0.15). There was an increase in all grades of aGVHD [HR 3.68 (2.16, 6.28), p < 0.001)] with RIC regimens, but only 12 events of grade III/IV aGVHD overall.

In multivariate analyses (with histology and ATG as covariates) NMA with rituximab had improved PFS compared to RIC without rituximab [HR 0.43 (95% CI 0.22, 0.81; p=0.009)]. However, PFS was similar comparing NMA and RIC groups [HR 0.72 (95% CI 0.37, 1.41; p=0.3)]. Similarly, aGVHD (any grade) risk was lower in NMA pts receiving rituximab compared to RIC pts who did not [HR 0.15 (0.07-0.32), p < 0.001). No significant differences were noted in NRM or CMV reactivation between groups.

Conclusions: Our study suggests that there are comparable and favorable outcomes between RIC and NMA conditioned allo-HCT for NHL with careful patient and regimen selection. Further studies are needed to better define specific criteria in choosing between NMA and RIC allo-HCT conditioning regimens for pts with NHL.

Disclosure: Gunjan Shah- Investigator + Research Funding for Janssen and Amgen

Michael Scordo- Consultancy: McKinsey & Company + Angiocrine Bioscience

Craig Sauter- Advisory Board, Honoraria and Research Funding: Juno + Sanofi-Genzyme + Celgene + Precision Biosciences. Advisory Board and Honoraria: Spectrum Pharmaceuticals + Novartis + Genmab + Kite + Gamida + Pfizer + GSK

Miguel Perales- MolMed: Advisory Board and Honoraria + NexImmune: Advisory Board and Honoraria + Abbvie: Advisory Board and Honoraria + Bellicum: Advisory Board and Honoraria + Bristol-Myers Squibb: Advisory Board and Honoraria + Incyte: Advisory Board, Honoraria and Research Funding + Nektar Therapeutics: Advisory Board and Honoraria + Novartis: Advisory Board and Honoraria + Omeros: Advisory Board and Honoraria + Takeda: Advisory Board and Honoraria + Kite: Research Funding + Merck: Consultancy and Honoraria + Servier: DSMB Honoraria + Medigene: DSMB Honoraria

Sergio Giralt - Amgen: Consultant and Investigator, Research Funding + Actinium: Consultant and Investigator, Research Funding + Celgene: Consultant and Investigator, Research Funding + Johnson & Johnson: Consultant and Investigator, Research Funding + Miltenyi: Investigator, Research Funding + Takeda: Consultant and Investigator, Research Funding + Consultant for Kite + Spectrum Pharmaceuticals + Jazz Pharmaceuticals + Novartis

¹National University Cancer Institute, National University Health System, Singapore, Singapore, ²Singapore General Hospital, Singapore, Singapore

Background: High relapse and graft failure rates have been seen with the Minnesota reduced-intensity conditioning (RIC) for umbilical cord blood transplantation (UCBT) regimen consisting of fludarabine (Flu) 200mg/m², cyclophosphamide (Cy) 50mg/kg and 2 Gy of total body irradiation (TBI). We evaluated a new thiotepa-based intensified RIC regimen consisting of Flu 150mg/m2, Cy 50mg/kg, thiotepa 10mg/kg, and 4Gy TBI, which has shown promising results with sustained engraftment and acceptable toxicity.

Methods: We performed a retrospective analysis of 90 adult patients in 2 institutions in Singapore receiving 4/6-6/6 HLA matched UCBT for various haematological malignancies between Aug 2006 and May 2019. Patients received 1 of 3 conditioning regimens - myeloablative Cond