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Acute myeloid leukemia (AML) has an aggressive course and a historically dismal prognosis. For many patients, hematopoietic stem cell transplantation (HSCT) represents the best option for cure, but access, utilization and health inequities on a global scale remain poorly elucidated.To describe patterns of global HSCT use in AML for a better understanding of global access, practices, and unmet needs internationally.Estimates of AML incident cases in 2016 were obtained from the Global Burden of Disease (GBD) 2019 study. HSCT activities were collected from 2009-2016 by the Worldwide Network for Blood and Marrow Transplantation (WBMT) through its member organizations. The primary endpoint was global and regional use (number of HSCT) and utilization of HSCT (number of HSCT/ number of incident cases) for AML. Secondary outcomes included trends from 2009 to 2016 in donor type, stem cell source and remission status at time of HSCT.Global AML incidence has steadily increased, from 102,000 (95% uncertainty interval (UI): 90,200-108,000) in 2009 to 118,000 (104,000-126,000) in 2016 (+16.2%). Over the same period, a +54.9% increase from 9,659 to 14,965 HSCT/year was observed globally, driven by an increase in allogeneic (+64.9%) with a reduction in autologous (-34.9%) HSCT. While the highest numbers of HSCT continue to be performed in high-resource regions, the largest increases were seen in resource-constrained regions [+94.6% in Africa/East Mediterranean Region (AFR/EMR); +34.7% in America-Nord Region (AMR-N)]. HSCT utilization was skewed towards high-resource regions [in 2016: AMR-N 18.4%, Europe (EUR) 17.9%, South-East Asia/Western Pacific Region (SEAR/WPR) 11.7%, America-South Region (AMR-S) 4.5% and AFR/EMR 2.8%]. For patients70 years of age, this difference in utilization was widened; AMR-N had the highest allogeneic utilization rate, increasing from 2009 to 2016 (30.6% to 39.9%) with continued low utilization observed in AFR/EMR (1.7% to 2.9%) and AMR-S (3.5% to 5.4%). Across all regions, total HSCT for AML in 1HSCT remains a central curative treatment modality in AML. Allogeneic HSCT for AML is rising globally but there are marked variations in regional utilization and practices, including types of graft source. Resource-constrained regions have the largest growth in HSCT use, but utilization rates remain low with a predilection for familial related donor sources and are typically offered in CR1. Further studies are necessary to elucidate the reasons, including economic factors, to understand and address these health inequalities and improve discrepancies in use of HSCT as a potentially curative treatment globally.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the gold standard curative therapy for infants and children with many inborn errors of immunity (IEI), but adolescents and adults with IEI are rarely referred for transplant. Lack of published HSCT outcome data outside small, single-center studies and perceived high risk of transplant-related mortality have delayed the adoption of HSCT for IEI patients presenting or developing significant organ damage later in life. This large retrospective, multicenter HSCT outcome study reports on 329 IEI patients (age range, 15-62.5 years at HSCT). Patients underwent first HSCT between 2000 and 2019. Primary endpoints were overall survival (OS) and event-free survival (EFS). We also evaluated the influence of IEI-subgroup and IEI-specific risk factors at HSCT, including infections, bronchiectasis, colitis, malignancy, inflammatory lung disease, splenectomy, hepatic dysfunction, and systemic immunosuppression. At a median follow-up of 44.3 months, the estimated OS at 1 and 5 years post-HSCT for all patients was 78% and 71%, and EFS was 65% and 62%, respectively, with low rates of severe acute (8%) or extensive chronic (7%) graft-versus-host disease. On univariate analysis, OS and EFS were inferior in patients with primary antibody deficiency, bronchiectasis, prior splenectomy, hepatic comorbidity, and higher hematopoietic cell transplant comorbidity index scores. On multivariable analysis, EFS was inferior in those with a higher number of IEI-associated complications. Neither age nor donor had a significant effect on OS or EFS. We have identified age-independent risk factors for adverse outcome, providing much needed evidence to identify which patients are most likely to benefit from HSCT. ispartof: BLOOD vol:140 issue:14 pages:1635-1649 ispartof: location:United States status: published

TP53 mutations (TP53MTs) have been associated with poor outcomes in various hematologic malignancies, but no data exist regarding its role in patients with myelofibrosis undergoing hematopoietic stem cell transplantation (HSCT). Here, we took advantage of a large international multicenter cohort to evaluate the role of TP53MT in this setting. Among 349 included patients, 49 (13%) had detectable TP53MT, of whom 30 showed a multihit configuration. Median variant allele frequency was 20.3%. Cytogenetic risk was favorable (71%), unfavorable (23%), and very high (6%), with complex karyotype present in 36 patients (10%). Median survival of patients with TP53MT was 1.5 vs 13.5 years for those with wild-type TP53 (TP53WT; P

We performed a study to find out how advances in modern medicine have improved the mortality risk of allogeneic stem cell transplantation. We analyzed major transplantation outcome parameters in adult patients on the European Society for Blood and Marrow Transplantation (EBMT) registry who had hematologic malignancies and had received transplants from matched sibling donors. We performed multivariate analyses using the Cox proportional-hazards model including known risk factors for nonrelapse mortality and a matched-pairs analysis. We identified 38 800 patients who fulfilled the inclusion criteria. Considerable changes in patient characteristics have occurred in the past decades, such as older age, different underlying diseases, and a higher proportion of patients with advanced disease. Major reasons for transplantation-related death in the 1980s were infectious complications and graft-versus-host disease. Nonrelapse mortality, measured at 1 year after transplantation, has decreased over time: 29.7% from 1980 through 1989, 24.4% from 1990 through 1999, 14.8% from 2000 through 2009, and 12.2% from 2010 through 2016. On multivariate analysis, the year of transplantation was associated with reduced nonrelapse mortality (P < .0001; hazard ratio [HR] [95% confidence interval (CI)], 0.8 [0.79-0.82], for 5-year intervals) and decreased overall mortality (P < .0001; HR [95% CI], 0.87 [0.86-0.88]. In the matched-pairs analysis of 3718 patients in each group, nonrelapse mortality at 1 year was 24.4% in the 1990s and 9.5% from 2013 through 2016 (P < .0001; HR [95% CI], 0.39 [0.34-0.43]). Transplantation-related mortality has decreased significantly in the past 40 years. These favorable data facilitate evidence-based treatment decisions on transplantation indications in the context of the availability of novel immunotherapies. ispartof: BLOOD ADVANCES vol:4 issue:24 pages:6283-6290 ispartof: location:United States status: published

Data on the association between chimeric antigen receptor (CAR)-T-cell kinetics and patient outcome in the nontrial setting are missing, mainly due to the lack of broadly available CAR-T-cell diagnostic quantification tools. We performed prospective quantification of axicabtagene ciloleucel (axi-cel) in 21 patients treated for aggressive B-cell lymphoma at our clinic. Median peak CAR-T-cell count was 16.14 CAR-T cells/µL. Patients with 16.14/μL or higher peak CAR-T cells (strong expanders) had more day-30 objective responses (91% vs 40%, P = .02). In univariate analysis, peak CAR-T cell ≥ 16.14 (P < .001), normal platelet counts at start of lymphodepletion (P < .001), no prior stem cell transplant (P = .04), and peak CAR-T cells as continuous variable (P = .03) were associated with better progression-free survival (PFS). After adjusting for platelet counts and prior stem cell transplantation, peak CAR-T cells below median was still associated with shorter PFS (relative risk, 0.15, 95% confidence interval, 0.04-0.59, P = .007). Low platelet counts also maintained significant impact on PFS. Our data demonstrate association of axi-cel levels and outcome in a nontrial setting and for the first time use a cutoff to segregate weak and strong expanders with respective outcomes.

Allogeneic hematopoietic stem cell transplantation is curative in myelofibrosis, and current prognostic scoring systems aim to select patients for transplantation. Here, we aimed to develop a prognostic score to determine prognosis after transplantation itself, using clinical, molecular, and transplant-specific information from a total of 361 patients with myelofibrosis. Of these, 205 patients were used as a training cohort to create a clinical-molecular myelofibrosis transplant scoring system (MTSS), which was then externally validated in a cohort of 156 patients. Multivariable analysis on survival identified age at least 57 years, Karnofsky performance status lower than 90%, platelet count lower than 150 × 109/L, leukocyte count higher than 25 × 109/L before transplantation, HLA-mismatched unrelated donor, ASXL1 mutation, and non-CALR/MPL driver mutation genotype being independent predictors of outcome. The uncorrected concordance index for the final survival model was 0.723, and bias-corrected indices were similar. Risk factors were incorporated into a 4-level MTSS: low (score, 0-2), intermediate (score, 3-4), high (score, 5), and very high (score, >5). The 5-year survival according to risk groups in the validation cohort was 83% (95% confidence interval [CI], 71%-95%), 64% (95% CI, 53%-75%), 37% (95% CI, 17%-57%), and 22% (95% CI, 4%-39%), respectively (P < .001). Increasing score was predictive of nonrelapse mortality (P < .001) and remained applicable to primary (0.718) and post-essential thrombocythemia (ET)/polycythemia vera (PV) myelofibrosis (0.701) improving prognostic ability in comparison with all currently available disease-specific systems. In conclusion, this MTSS predicts outcome of patients with primary and post-ET/PV myelofibrosis undergoing allogeneic stem cell transplantation.

Allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for myelofibrosis (MF). In this large multicenter retrospective study, overall survival (OS) in MF patients treated with allogeneic HCT (551 patients) and without HCT (non-HCT) (1377 patients) was analyzed with Cox proportional hazards model. Survival analysis stratified by the Dynamic International Prognostic Scoring System (DIPSS) revealed that the first year of treatment arm assignment, due to upfront risk of transplant-related mortality (TRM), HCT was associated with inferior OS compared with non-HCT (non-HCT vs HCT: DIPSS intermediate 1 [Int-1]: hazard ratio [HR] = 0.26, P < .0001; DIPSS-Int-2 and higher: HR, 0.39, P < .0001). Similarly, in the DIPSS low-risk MF group, due to upfront TRM risk, OS was superior with non-HCT therapies compared with HCT in the first-year post treatment arm assignment (HR, 0.16, P = .006). However, after 1 year, OS was not significantly different (HR, 1.38, P = .451). Beyond 1 year of treatment arm assignment, an OS advantage with HCT therapy in Int-1 and higher DIPSS score patients was observed (non-HCT vs HCT: DIPSS-Int-1: HR, 2.64, P < .0001; DIPSS-Int-2 and higher: HR, 2.55, P < .0001). In conclusion, long-term OS advantage with HCT was observed for patients with Int-1 or higher risk MF, but at the cost of early TRM. The magnitude of OS benefit with HCT increased as DIPSS risk score increased and became apparent with longer follow-up.

Acute graft-versus-host disease (GVHD) is treated with systemic corticosteroid immunosuppression. Clinical response after 1 week of therapy often guides further treatment decisions, but long-term outcomes vary widely among centers, and more accurate predictive tests are urgently needed. We analyzed clinical data and blood samples taken 1 week after systemic treatment of GVHD from 507 patients from 17 centers of the Mount Sinai Acute GVHD International Consortium (MAGIC), dividing them into a test cohort (n = 236) and 2 validation cohorts separated in time (n = 142 and n = 129). Initial response to systemic steroids correlated with response at 4 weeks, 1-year nonrelapse mortality (NRM), and overall survival (OS). A previously validated algorithm of 2 MAGIC biomarkers (ST2 and REG3α) consistently separated steroid-resistant patients into 2 groups with dramatically different NRM and OS (P < .001 for all 3 cohorts). High biomarker probability, resistance to steroids, and GVHD severity (Minnesota risk) were all significant predictors of NRM in multivariate analysis. A direct comparison of receiver operating characteristic curves showed that the area under the curve for biomarker probability (0.82) was significantly greater than that for steroid response (0.68, P = .004) and for Minnesota risk (0.72, P = .005). In conclusion, MAGIC biomarker probabilities generated after 1 week of systemic treatment of GVHD predict long-term outcomes in steroid-resistant GVHD better than clinical criteria and should prove useful in developing better treatment strategies.

Despite significantly improved preventive measures, acute graft-versus-host disease (aGVHD) remains as one of the most frequent complications after allogeneic hematopoietic stem cell transplantation (HCT). Its clinical grading is determined by the evaluation of its primarily affected organs, namely skin, liver and the gastro-intestinal tract. A number of existing grading systems, of which the 'Keystone Consensus' (Przepiorka D et al. BMT 1994) and MAGIC grading systems (Harris AC et al. BBMT 2016) are the most customary, have been proposed over the years to evaluate aGVHD severity based on the extent of aGVHD organ involvement. However, limitations remain regarding its association with clinical outcome. In the current era, particularly consensus grades I and II aGVHD are hardly distinguishable with respect to overall survival (OS). Given the discrepancies in aGVHD grading, we hypothesized that a data-driven approach would support the understanding and classification of aGVHD with respect to organ involvement, clinical outcome and risk cohorts. Here, we validated on a large, multi-national EBMT cohort a novel data-driven grading system for aGVHD that was previously developed by unsupervised learning applying principal component analysis on aGVHD organ stages (Turki AT et al. EHA 2020). The resulting Machine Learning (ML) aGVHD grading had 12 stages that were divided into 4 balanced ML-aGVHD grades to assess the severity of aGVHD, different from conventional grading. Our study included 19,617 adult patients with first HCT for hematologic malignancies between 2009 and 2018 and evidence of aGVHD. All donors except cord blood HCT were included. Detailed aGVHD organ involvement were required for the calculation of the ML-aGVHD score. Exclusion criteria were missing information on aGVHD organ involvement or follow up and very late onset aGVHD (> d+180). The baseline characteristics of this cohort reflect current HCT practice, with acute myeloid leukemia (55.3%) as predominant disease and a majority of unrelated donor HCT recipients (63.7%). Myeloablative conditioning was used in 46.7% of patients. In addition to baseline calcineurin inhibitors, 60.6% of patients received in-vivo T cell depletion with ATG or Campath. The ML-aGVHD grading distinguished 12 ML stages with significantly different clinical outcomes for OS (Figure 1a), non-relapse mortality (NRM) and relapse. The 4 ML-aGVHD grades (ML-I, stages 1-3; ML-II stages 4-6; ML-III, stages 7-9; ML-IV stages 10-12) revealed highly significant and clinically relevant differences for OS and NRM (p Figure 1 Figure 1. Disclosures Turki: CSL Behring: Consultancy; Jazz Pharma: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau. Penack: Omeros: Consultancy; Shionogi: Consultancy; Priothera: Consultancy; Incyte: Research Funding; Takeda: Research Funding; Therakos: Honoraria; Pfizer: Honoraria; Neovii: Honoraria; Novartis: Honoraria; MSD: Honoraria; Jazz: Honoraria; Gilead: Honoraria; Astellas: Honoraria. Schoemans: Janssen: Membership on an entity's Board of Directors or advisory committees; CIBMTR: Consultancy, Other: travel grants; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: personal fees , Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Travel grants and personal fees; Gilead: Other: travel grants; BHS: Membership on an entity's Board of Directors or advisory committees, Other: travel grants and personal fees , Research Funding; Jazz Pharmaceuticals: Other: personal fees; Takeda: Other: personal fees. Socie: Alexion: Research Funding. Reinhardt: Abbvie: Consultancy; AstraZeneca: Consultancy; Vertex: Consultancy; Merck: Consultancy; Gilead: Research Funding; CDL Therapeutics: Current holder of individual stocks in a privately-held company. Blaise: Jazz Pharmaceuticals: Honoraria. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Mielke: DNA Prime SA: Speakers Bureau; Gilead/KITE: Other: Travel support, Expert panel ; Miltenyi: Other: Data safety monitoring board; Novartis: Speakers Bureau; Celgene/BMS: Speakers Bureau; Immunicum: Other: Data safety monitoring board. Yakoub-Agha: Jazz Pharmaceuticals: Honoraria. Forcade: MSD: Other: Travel Support; Jazz: Other: Travel Support, Speakers Bureau; Gilead: Other: Travel Support, Speakers Bureau; Novartis: Consultancy, Other: Travel Support, Speakers Bureau. Basak: Saventic Health: Current holder of individual stocks in a privately-held company. Perić: therakos: Honoraria; servier: Honoraria; MSD: Honoraria; Astellas: Honoraria; NOVARTIS: Honoraria; Abbvie: Honoraria; Pfizer: Honoraria.

Introduction Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment option in patients with advanced Chronic Myeloid Leukemia (CML) who have disease resistant to tyrosine kinase inhibitors (TKI) or who cannot tolerate these agents. In the absence of a matched sibling donor (MSD), the use of an unrelated donor (UD) is recommended; however, this approach is associated with a higher incidence of both graft-versus-host disease (GvHD) and non-relapse mortality (NRM). Post-transplant cyclophosphamide (PTCy) has been found to result in similar rates of GvHD-free, relapse-free survival (GRFS) in allo-HCT using UD, haploidentical donors (HD) and MSD across a range of haematological malignancies. However, the role of PTCy in allo-HCT using UD and HD in CML is unknown. We here report an observational, retrospective, comparative study on the role of PTCy in UD and HD in CML patients undergoing allo-HCT. Methods Inclusion criteria were age ≥ 18 years, diagnosis of CML, first AlloHCT from 2012 to 2019, and UD and HD. The main endpoints of the study were to compare the one-year GRFS of allo-HCT using UD with standard GvHD prophylaxis (SP), PTCy UD and PTCy HD. Secondary endpoints were 3-year OS, 3-year PFS, 3-year NRM, 3-year RI, Day +100 acute GvHD (aGvHD) and one-year chronic GvHD (cGvHD). The Kaplan-Meier estimator and log-rank test were used for GRFS, OS and PFS, and the crude cumulative incidence estimator and Gray's test were used for competing events (RI/NRM, aGvHD/death before aGvHD and cGvHD/death before cGvHD). Cox proportional hazard regression was used in multivariable analyses (MVA) using patients with complete data with cause-specific models for competing risk outcomes. Results A total of 1,341 CML patients treated in EBMT centers were included. 1,094 patients received allo-HCT from SP UD, 113 from PTCy UD and 134 from PTCy HD. 61% and 54% of patients received an allo-HCT from matched UD in the SP UD and PTCy UD cohort, respectively. SP UD GvHD prophylaxis was calcineurin inhibitor-based in 88% of patients; some form of T-cell depletion was used in 82%, 19% and 9% in the SP UD, PTCy UD, and PTCy HD cohorts, respectively. Further transplant and patient details can be found in Table 1. The median follow-up was 34.9 (IQR 13.2-61.2) months. One-year GRFS was comparable in the three cohorts: 56%, 53% and 48% in SP UD, PTCy UD, and PTCy HD, respectively (log-rank p=0.30). There was no significant difference in the cumulative incidence of aGvHD at D+100 (Gray's test p=0.10) and one-year cGvHD (p=0.40) among cohorts. Conversely, the 3-year relapse incidence (RI) was significantly lower in the SP UD cohort (26%), compared to the PTCy UD (35%) and PTCy HD (34%) cohorts (Gray's test p=0.03) and the 3-year progression-free survival (PFS) was 53% vs 47% vs 45% in the SP UD, PTCy UD and PTCy HD cohorts, respectively (log-rank p=0.05). 3-year NRM was similar among cohorts 20% vs 18% vs 21% in SP UD, PTCy UD and PTCy HD, respectively (Gray's test p=0.80) and the three cohorts had a similar 3-year OS (64%, 60% and 59% in SP UD, PTCy UD and PTCy UD, respectively) (p=0.50). In total 902 patients (68%) had complete data. In MVA, higher age (HR per 10 year increase in age 1.24, 95% CI 1.06-1.45, p=0.007) and high HCT-CI (HR high vs. low 2.43, 1.59-3.71, p Conclusion Based on our results, PTCy resulted in comparable outcomes in UD and HD allo-HCT, when compared to SP UD allo-HCT, as GRFS, PFS, NRM and OS were similar. However, there was a trend to a lower RI and higher PFS in SP UD allo-HCT which may have reached significance in a larger cohort. Furthermore, the findings of this study confirm that PTCy HD allo-HCT in CML is a valid option for patients lacking a MSD or UD. In addition, disease stage pre-transplant remains a major prognostic factor with CP1 patients having better outcomes when compared to those with more advanced phases and ≥CP1 CML. Overall, our results provide information on the efficacy of PTCy in allo-HCT for CML, and show that PTCy UD and PTCy HD are feasible allo-HCT platforms for patients diagnosed with CML. Figure 1 Figure 1. Disclosures Ortí: BMS, Novartis, Incyte, Pfizer: Honoraria, Speakers Bureau. Kulagin: X4 Pharmaceuticals, Alexion, Apellis, Biocad: Research Funding; Novartis, Generium, Sanofi, Roche, Johnson & Johnson, Pfizer: Speakers Bureau. Apperley: Bristol Myers Squibb, Novartis: Honoraria, Speakers Bureau; Incyte, Pfizer: Honoraria, Research Funding, Speakers Bureau. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Bloor: Kite, a Gilead Company: Honoraria; Novartis: Honoraria. Angelucci: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene BSM: Honoraria, Other: DMC; Blue Bird Bio: Honoraria, Membership on an entity's Board of Directors or advisory committees; Menarini-Stemline: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: steering commitee, Speakers Bureau; Vertex Pharmaceuticals: Honoraria, Other: DMC; Crispr therapeutics: Honoraria, Other: DMC; Glaxo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees. Blaise: Jazz Pharmaceuticals: Honoraria. Lopez Corral: Gilead, Novartis: Consultancy, Honoraria. Anagnostopoulos: Abbvie: Other: clinical trials; Sanofi: Other: clinical trials ; Ocopeptides: Other: clinical trials ; GSK: Other: clinical trials; Incyte: Other: clinical trials ; Takeda: Other: clinical trials ; Amgen: Other: clinical trials ; Janssen: Other: clinical trials; novartis: Other: clinical trials; Celgene: Other: clinical trials; Roche: Other: clinical trials; Astellas: Other: clinical trials . Wrobel: Janssen: Honoraria, Speakers Bureau; Roche: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; BeiGene: Honoraria, Speakers Bureau. Rigacci: Merck: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accomodations, Expenses; Gilead Science: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hayden: Jansen, Takeda: Other: Travel, Accomodation, Expenses; Amgen: Honoraria. Chalandon: Incyte, BMS, Pfizer, Abbie, MSD, Roche, Novartis, Amgen: Other: Advisory Board; Incyte: Speakers Bureau; Incyte, BMS, Pfizer, Abbie, MSD, Roche, Novartis, Gilead, Amgen, Jazz, Astra Zenec: Other: Travel EXpenses, Accomodation. Yakoub-Agha: Jazz Pharmaceuticals: Honoraria.

Isocitrate dehydrogenase (IDH) 1 and 2 mutations occur in 20% of acute myeloid leukemia (AML). Patients with AML carrying IDH1-2 mutations have a similar prognosis compared to patients without these mutations (DiNardo et al, AM J H, 2015). However, the impact of IDH1-2 mutations on patients with AML undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT) is not well known. In this study, we investigate the prognostic impact of IDH1-2 mutational status on AML patients undergoing alloHCT in complete remission (CR). In this retrospective registry-based analysis, we identified 710 consecutive adult patients (46.2% female; median age: 58.5 years [range, 18-78]) with AML undergoing allo-HCT in CR between 2015 and 2019 at 85 EBMT participating centers. Cord blood, ex-vivo graft manipulated transplants, and patients with favorable cytogenetics were excluded. Median follow-up was 15 months [95% CI 13.4-16.6]. Patients were categorized based on IDH1-2 mutational status, with 300 (42%) mutated and 410 (58%) wild type. Six hundred and fifty-two (92%) and 58 (8%) patients had de novo and secondary AML, respectively, and 141 (20%) patients had poor-risk cytogenetics. IDH1-2 mutation was positively correlated with NPM1 mutation (40% in IDH1-2 mutated vs 27% in wild type, p=0.0001) and more frequently encountered in middle-aged patients (p=0.01). No correlation was noted between IDH1-2 and FLT3 mutation or other patient characteristics. Minimal residual disease (MRD) data was available for 344 patients, 53% of which were MRD-negative at transplant in both groups. Six hundred and twenty-three (88%) and 87 (12%) patients were in first and second CR at time of transplant, respectively. Patients received grafts from a matched sibling (24%), unrelated (62%), or haploidentical (14%) donor, and myeloablative conditioning (MAC) was used in 42%. Ninety-three percent of the patients received peripheral blood as the stem cell source. At day 180, the cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was significantly lower in IDH1-2 mutated compared to wild-type patients (22% vs 33%, p=0.002). No differences in chronic GVHD rates were noted between the 2 groups (39% vs 40%, p=0.87). The 2-year cumulative relapse incidence (RI) was significantly lower and the GVHD-free, relapse-free survival (GRFS) was also improved in IDH1-2 mutated compared to wild-type patients (14.4% vs 27%, p=0.001 and 47% vs 39%, p=0.006, respectively). This led to an improved leukemia-free survival (LFS) in IDH1-2 patients (69% vs 59%, p=0.01), however, it did not translate into an overall survival (OS) difference. No significant difference was noted in non-relapse mortality (NRM) between the 2 groups (17% vs 14.2%, p=0.26). These findings were confirmed in multivariate analysis. In fact, IDH1-2 mutation was associated with significant improvement in RI (hazard ratio [HR]=0.4 [95%CI 0.25-0.64], p=0.0001), LFS (HR=0.7 [95%CI 0.51-0.95], p=0.022), aGVHD II-IV (HR=0.63 [95%CI 0.45-0.87], p=0.005) and GRFS (HR=0.69 [95%CI 0.54-0.89], p=0.004). Conversely, the presence of adverse cytogenetics and undergoing allo-SCT in second CR increased the RI (HR=2.29 [95%CI 1.46-3.61], p=0.0003 and HR=2.84 [95%CI 1.64-4.91], p=0.0002, respectively) and were associated with a shorter LFS (HR=1.67 [95%CI 1.18-2.36], p=0.004 and HR=1.61 [95%CI 1.06-2.44], p=0.025) while reduced intensity (RIC) conditioning had a worse impact on OS compared to MAC (HR=1.56 [95%CI 1.07-2.29], p=0.022). Additionally, in the subgroup of patients with available MRD data, MRD positivity at transplant significantly increased RI (HR=2.15 [95%CI 1.09-4.23], p=0.027) with no impact on survival. In conclusion, our data suggest that the presence of IDH1-2 mutations acts as an independent prognostic factor and is associated with improved outcome in patients with AML in CR undergoing allo-HCT. Indeed, patients with IDH1-2 mutations had significantly lower rates of RI and aGVHD, which translated into improved LFS and GRFS. Nevertheless, patients with MRD positivity at time of transplant had significantly increased RI. Further studies investigating allo-HCT outcomes in IDH1-2 mutated patients with AML in the era of IDH inhibitors (both in the pre- and post-transplant setting) would help to further define the impact of these mutations in this setting and thus optimize an individualized treatment approach. Disclosures Labopin: Jazz Pharmaceuticals: Honoraria. Esteve: Abbvie: Consultancy; Pfizer: Consultancy; Astellas: Consultancy; Novartis: Research Funding; Novartis: Consultancy, Research Funding; Bristol Myers Squibb/Celgene: Consultancy; Jazz: Consultancy. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Blaise: Jazz Pharmaceuticals: Honoraria. Socie: Alexion: Research Funding. Ganser: Jazz Pharmaceuticals: Honoraria; Novartis: Honoraria; Celgene: Honoraria. Yakoub-Agha: Jazz Pharmaceuticals: Honoraria. Bazarbachi: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Hikma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees.

Introduction Although the labeled CD19 targeting CAR-T cell constructs axi-cel and tisa-cel are generally associated with an acceptable safety profile, non-relapse deaths can occur. Little is known about timing, causes and predictors of NRM following SOC CAR-T cell therapy for LBCL. Here, we analyzed frequency, causes, and risk factors of non-relapse deaths with focus on late NRM (beyond 4 weeks after dosing) using registry data provided by the DRST, the national partner of the EBMT. Methods Patients were selected from 356 consecutive patients who received SOC CAR-T treatment of LBCL between November 2018 and April 2021 at 21 German centers and were registered with the DRST/EBMT. Baseline patient, disease, and transplant data were collected from MED-A cellular therapy forms. Centers were contacted to provide additional treatment and follow-up information. Patients with late NRM (defined as NRM occurring beyond 4 weeks after dosing without prior LBCL relapse or progression) were compared with all patients surviving progression-free the 4-week landmark after dosing without subsequent NRM. Cumulative incidences of NRM were calculated considering relapse/progression as competing event. Results The analysis set consisted of 312 patients surviving progression-free at least 28 days after CAR-T treatment and remained alive until the end of follow-up or had a documented cause of death. Median age was 61 years (19-83), 66% were male, 52% had an IPI ≥3, 13 had an ECOG score >1, 70% had received ≥3 treatment lines, 33% had failed a prior HCT, and 78% were refractory at lymphodepletion. 50% had been treated at a center contributing ≥20 cases with axi-cel (52%) or tisa-cel (48%). Grade ≥3 CRS and grade ≥3 neurotoxicity (NT) had occurred in 11% each, and 7% had no neutrophil recovery at day 100 post dosing or at last follow-up, whatever was earlier. With a median follow-up of 11.2 months, 124 patients (40%) had died, 109 (35%) LBCL-related, and 15 (5%) because of NRM. The cumulative incidence of late NRM at 12 months post dosing was 4.3% (95%CI 2.0-6.6). Causes of NRM were infections in 10 patients (bacterial or fungal sepsis/pneumonia 6; viral/atypical pneumonia/encephalitis 4); late NT 2; hyperinflammatory syndrome 1; 2 nd malignancy 1; unknown 1). Of note, 5 of the 6 lethal fungal/bacterial infections occurred subsequent to high grade NT. There was no significant difference between patients experiencing and not experiencing NRM in terms of age, gender, IPI, ECOG, pretreatment lines, prior HCT, disease status at lymphodepletion, and grade ≥3 CRS frequency. However, a significantly larger proportion of patients with late NRM had failed neutrophil recovery (27% vs 5%, p 0.011), had experienced grade ≥3 NT (40% vs 10%, p 0.0031), and/or had received axi-cel (93% vs 51%, p 0.001). Patients having neutrophil non-recovery and/or grade ≥3 NT had a 12-month NRM incidence of 16% (95%CI 5.1-26.9) vs 2.5% (95%CI 0.3-4.7) in patients with none of these 2 factors. Conclusions Late NRM in patients receiving SOC CAR-T treatment for LBCL is largely driven by infections. Risk factors for late NRM appear to be protracted neutropenia and higher grade NT, suggesting that intensified anti-bacterial/anti-fungal prophylaxis may be considered in patients with persisting critical neutropenia or exposed to high-dose steroids for NT treatment. Figure 1 Figure 1. Disclosures Dreger: BMS: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; Bluebird Bio: Consultancy; AbbVie: Consultancy, Speakers Bureau; Gilead Sciences: Consultancy, Speakers Bureau; Janssen: Consultancy; Novartis: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Schubert: Gilead: Consultancy. Holtick: Sanofi: Honoraria; Celgene: Honoraria. Subklewe: Miltenyi: Research Funding; Takeda: Speakers Bureau; Gilead: Consultancy, Research Funding, Speakers Bureau; Klinikum der Universität München: Current Employment; MorphoSys: Research Funding; Novartis: Consultancy, Research Funding, Speakers Bureau; Roche: Research Funding; Seattle Genetics: Consultancy, Research Funding; Pfizer: Consultancy, Speakers Bureau; Janssen: Consultancy; BMS/Celgene: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau. Bastian: Abbvie: Other; Amgen: Consultancy, Honoraria; Astra Zeneca: Honoraria, Other; BMS and Celgene: Consultancy, Honoraria, Other; Kite-Gilead: Consultancy, Honoraria; MSD: Consultancy, Honoraria, Other, Research Funding; Novartis: Consultancy, Honoraria, Other, Research Funding; Pentixafarm: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Other, Research Funding. Ayuk: Gilead: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Takeda: Honoraria; Miltenyi Biomedicine: Honoraria; Mallinckrodt/Therakos: Honoraria, Research Funding; Novartis: Honoraria. Marks: Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Honoraria; Merck: Consultancy; AbbVie: Other: Meeting attendance. Penack: Priothera: Consultancy; Takeda: Research Funding; Incyte: Research Funding; Neovii: Honoraria; Pfizer: Honoraria; Therakos: Honoraria; Novartis: Honoraria; MSD: Honoraria; Jazz: Honoraria; Gilead: Honoraria; Astellas: Honoraria; Shionogi: Consultancy; Omeros: Consultancy. Koenecke: EUSA Pharm: Consultancy; Kite/Gilead: Consultancy; BMS/Celgene: Consultancy; Janssen: Consultancy; Novartis: Consultancy. Von Bonin: Daiichi Sankyo: Other: traveling support and advisory fees; Novartis: Other: traveling support and advisory fees; Kite/Gilead: Other: traveling support and advisory fees. Stelljes: Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Glass: BMS: Consultancy; Helios Klinik Berlin-Buch: Current Employment; Kite: Consultancy; Novartis: Consultancy; Riemser: Research Funding; Roche: Consultancy, Research Funding, Speakers Bureau. Baldus: Novartis: Honoraria; Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria. Vucinic: MSD: Honoraria; Novartis: Honoraria; Gilead: Honoraria, Other: Travel Sponsoring; Janssen: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring. Topp: Universitatklinikum Wurzburg: Current Employment; Celgene: Consultancy, Research Funding; Janssen: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy, Research Funding; Gilead: Research Funding; Regeneron: Consultancy, Research Funding; Macrogeniecs: Research Funding; Amgen: Consultancy, Research Funding. Schroers: BMS/Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Takeda: Honoraria. Hanoun: AstraZeneca: Honoraria; Abbvie: Other: travel expenses; Novartis: Research Funding. Thomas: AbbVie: Honoraria, Speakers Bureau; Art tempi: Honoraria, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Other, Research Funding, Speakers Bureau; EUSA Pharma: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other; Kite/Gilead: Honoraria, Other, Research Funding, Speakers Bureau; Medigene: Consultancy, Honoraria, Other; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other; Pfizer: Consultancy, Honoraria, Other, Speakers Bureau. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Bethge: Novartis: Consultancy, Honoraria, Speakers Bureau; Miltenyi Biotec: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kite-Gilead: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau.

Introduction: Data on the influence of different ATLG doses on immune reconstitution (IR) and GvHD in MUD allo-SCT is limited. In this study, we compared the impact of ATLG doses (30mg/kg vs 60 mg/kg) on IR and transplant outcomes. Methods: In this retrospective study we included 289 patients who received MUD allografts (HLA 10/10) between 2005-2019 in the University Cance Center University of Hamburg. All patients received PBSC-allo-SCT with MAC for various hematological malignancies. Seventy-three patients received 30mg/kg ATLG, and 216 patients received 60mg/kg (on days -3.-2 and -1) prior to allo-SCT. Periphereal blood samples were collected on days +30, +100 and +180 and analyzed by flow cytometry for following lymphocyte populations: T-cells (total and activated), T-helper cells (total, naïve and memory), cytotoxic T-cells (total, naïve and memory), B-Lymphocytes (total, naïve and memory), NK-cells, NKT-cells, γδT-cells and regulatory T-cells. Results: Neutrophil and platelet engraftments were significantly delayed after the 60mg/kg compared to 30mg/kg group with medians of 11 days (range, 8-23) vs 12 days (8-27) (p=0.009) for neutrophil and 14 days (range, 9-53) vs 16 days (range, 8-237) for platelets, respectively (p=0.002). We observed a higher incidence of EBV reactivation within the first 100 days in the 60mg/kg group (41% vs 21% in the 30mg/kg group, p=0.049). Higher cumulative incidence of Infections Day +100 was observed in the 60 mg/Kg group with an incidence of 75% vs that of 67% in the 30mg/Kg group respectively (p=0.002). At day +30 we observed a faster reconstitution of naïve-B cells (p The incidence of aGVHD grade II-IV was comparable between the groups: 63% and 59% in the 30mg/Kg and 60mg/Kg groups, respectively. We observed a higher incidence of grade IV aGvHD in the 30mg/kg group (8%) comparing with the rate of 0.5% in the 60mg/kg group (p=0.0002), this was confirmed in multivariate analysis: RR 0.65 (95%CI 0.005-0.363) p= 0.004. After a median follow up of 21 months (range, 1-161) there were no significant differences in OS, PFS, NRM, RI and cGVHD between the groups. Conclusion: The choice of ATLG dose has significant impact on IR after MUD-allo-SCT. Higher doses are associated with reduced severe aGVHD, however at the cost of delaying engraftment and increasing infections. Disclosures Ayuk: Celgene/BMS: Honoraria; Gilead: Honoraria; Janssen: Honoraria; Mallinckrodt/Therakos: Honoraria, Research Funding; Miltenyi Biomedicine: Honoraria; Novartis: Honoraria; Takeda: Honoraria.

BACKGROUND: Allogeneic hematopoietic cell transplantation (allo-HCT) is a standard of care for adults with high-risk acute lymphoblastic leukemia (ALL) in first or subsequent complete remission (CR). Myeloablative total body irradiation (TBI) combined with cyclophosphamide (Cy) is the most frequently used conditioning regimen. In order to reduce toxicity Cy may be replaced by fludarabine (Flu). The goal of this registry-based, retrospective study was to compare outcomes of allo-HCT following TBI/Cy vs. TBI/Flu conditioning. PATIENTS AND METHODS: Included in the analysis were 2255 patients aged 18-65 years, treated with allo-HCT from either a matched sibling (43%) or unrelated (57%) donor in CR1 (83%) or CR2 (17%), between the years 2010-2020. Patients with Ph(-) B-ALL, Ph(+) B-ALL, and T-ALL were represented in equal proportions. TBI 12Gy + Cy was used in 2105 cases while TBI 12Gy + Flu was administered to 150 patients. Patients treated with TBI/Flu were significantly older (median 35 years vs. 33 years, p=0.006), with poorer Karnofsky performance score ( RESULTS: Engraftment rate was 99% for both TBI/Cy and TBI/Flu patients. In a univariate analysis the use of TBI/Cy as compared to TBI/Flu was associated with a tendency to reduced incidence of relapse (24% vs. 29% at 2 years, p=0.1), increased incidence of grade 2-4 acute graft versus host disease (GVHD, 35.5% vs. 28%, p=0.08) and improved leukemia-free survival (LFS, 62% vs. 57%, p=0.18). The rates and causes of non-relapse mortality (NRM) did not differ significantly between the two conditioning groups. In a multivariate model adjusted for other prognostic factors, TBI/Cy conditioning was associated with reduced risk of relapse (HR=0.69, p=0.049) and increased risk of grade 2-4 acute GVHD (HR=1.57, p=0.03) without significant effect on other transplantation outcomes. An additional analysis was performed with TBI/Cy treated patients (n=132) matched strictly to those treated with TBI/Flu (n=132) in terms of disease subtype, disease status and donor type with the nearest neighbor for patient age, patient and donor sex, in vivo T-cell depletion, Karnofsky score and source of stem cells; the use of TBI/Cy as compared to TBI/Flu was associated with significantly reduced rate of relapse (18% vs. 30% at 2 years, p=0.015) and a tendency to an improved LFS (65% vs. 59%, p=0.07) and overall survival (OS, 73% vs. 68%, p=0.16) without effect on NRM and GVHD. CONCLUSIONS: The use of myeloablative TBI/CY as conditioning prior to allo-HCT for adult patients with ALL in CR1 or CR2 is associated with stronger anti-leukemic effect leading to significantly lower relapse rate compared to TBI/Flu and therefore should be likely considered a preferable regimen. Disclosures Giebel: Janssen: Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau. Labopin: Jazz Pharmaceuticals: Honoraria. Socie: Alexion: Research Funding. Yakoub-Agha: Jazz Pharmaceuticals: Honoraria. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Forcade: Novartis: Consultancy, Other: Travel Support, Speakers Bureau; Gilead: Other: Travel Support, Speakers Bureau; Jazz: Other: Travel Support, Speakers Bureau; MSD: Other: Travel Support. Huynh: Jazz Pharmaceuticals: Honoraria. Spyridonidis: Menarini: Current Employment. Perić: therakos: Honoraria; servier: Honoraria; MSD: Honoraria; Astellas: Honoraria; NOVARTIS: Honoraria; Abbvie: Honoraria; Pfizer: Honoraria. Mohty: Pfizer: Honoraria; Celgene: Honoraria, Research Funding; Amgen: Honoraria; Astellas: Honoraria; Gilead: Honoraria; Jazz: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Novartis: Honoraria; Bristol Myers Squibb: Honoraria; Takeda: Honoraria; Sanofi: Honoraria, Research Funding; Adaptive Biotechnologies: Honoraria.

Introduction. Malignant diseases treated with allogeneic hematopoietic stem cell transplantation (alloHSCT) predominantly occur beyond the 7 th decade of life. Numerical age per se is not regarded an adverse risk factor in alloHSCT. In an aging society, interventions historically deemed high risk are increasingly used in elder patients. Methods. Epidemiology, outcomes and risk factors of patients aged ≥70 years undergoing alloHSCT in Germany 1999-2019 and registered with the DRST/EBMT database were analyzed retrospectively. Baseline patient, disease, and transplant data were collected from MED-A forms. Centers were contacted to provide additional treatment and follow-up information. Results. Between 1999 and 2019, 1648 patients aged ≥70 years (median 72, range 70-79.7; 585 female) were transplanted in 50 German centers. More than 90% of all patients were transplanted 2010-2019. Centers transplanted between 2 and 192 patients, with 14 centers contributing 100 patients each. Most patients suffered acute leukemia (1084, 65.8%) or MDS/MPN (410, 24.9%). Karnofsky index before start of conditioning was 100% (n=230, 14%), 90% (n=651, 39.5%), 80% (n=480, 29.1%), 70% (n=94, 5.7%), Conclusion. AlloHSCT is increasingly used to treat elder patients in Germany with a sharp increase during the last decade. Age per se is a modest adverse risk factor for adult patients after alloHSCT with slightly increased mortality in patients 70-80 versus those at 60-69. Further research might concentrate on patient selection and further reduction of procedural toxicity. Figure 1 Figure 1. Disclosures Schetelig: Roche: Honoraria, Other: lecture fees; Novartis: Honoraria, Other: lecture fees; BMS: Honoraria, Other: lecture fees; Abbvie: Honoraria, Other: lecture fees; AstraZeneca: Honoraria, Other: lecture fees; Gilead: Honoraria, Other: lecture fees; Janssen: Honoraria, Other: lecture fees . Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Stelljes: Pfizer: Consultancy, Research Funding, Speakers Bureau; Medac: Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Dreger: AbbVie: Consultancy, Speakers Bureau; Bluebird Bio: Consultancy; Novartis: Consultancy, Speakers Bureau; Janssen: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; Gilead Sciences: Consultancy, Speakers Bureau; BMS: Consultancy; Riemser: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Wulf: Takeda: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Clinigen: Consultancy, Honoraria. Scheid: Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Honoraria; Roche: Consultancy; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bethge: Novartis: Consultancy, Honoraria, Speakers Bureau; Kite-Gilead: Consultancy, Honoraria, Speakers Bureau; Miltenyi Biotec: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau.

Introduction Patients with relapsed/refractory (r/r) AML have in general a dismal prognosis. Allogeneic stem cell transplantation (allo-SCT) provides a curative approach for these patients, however the overall survival (OS) remains still low achieving 20-40%. Though post-transplant minimal residual disease (MRD) monitoring has been shown to be predictive for development of post-transplant relapses and lower survival, data focusing on pre-transplant relapsed/refractory AML patients is scarce. In this study, we investigated the impact of achieving MRD negativity on day +100 for relapses and survival for this high risk patients. Patients and Methods We analyzed post-transplant outcomes for pre-transplant r/r AML patients depending on their post-transplant MRD status at day +100. The day +100 was chosen concerning the possibility of early post-transplant interventions (e.g. tapering of immunosuppression or administration of donor lymphocytes). Fifty six consecutive adult patients (≥18 years old) with r/r AML (median age 58, range 20-76; male, n=34, 61%) who underwent allo-SCT (first, n=44, 79%; second, n=12, 21%) between 2015-2020 at the Department for Stem Cell Transplantation at the University Medical Center Hamburg (Germany) were included. The MRD was assessed on day +100 using multiparameter flow cytometry according to "different from normal" strategy. The patients experienced rather primary refractory disease (64%), secondary/therapy-related AML (55%) and abnormal cytogenetics (59%) at diagnosis. The median pre-transplant blast count was 25% (6-91%). A number of 29 patients (52%) showed blasts in peripheral blood. Myeloablative conditioning was used in 31 (55%) patients, whereas 25 (45%) patients received reduced intensity regimens. A number of 29 patients (52%) received a FLAMSA-based conditioning. Post-transplant donor lymphocyte infusions as well as other treatment were given to 13 (23%) and 17 (30%) patients, respectively. Results The median follow up was 20 months (range 4-66). Forty patients (71%) achieved MRD negativity on day +100 and 16 (29%) remained MRD positive. The 2-year OS, LFS, relapses and NRM at 2 years for day +100 MRD negative patients were: 76% (95% CI: 60-87%), 59% (95% CI: 41-75%), 31% (95% CI: 17-50%) and 8% (95% CI: 3-19%), respectively. The 2-year OS, LFS, relapses and NRM at 2 years for day +100 MRD positive patients were: 35% (95% CI: 17-59%, p=p=0.001), 23% (95% CI: 9-46%, p Several factors were evaluated for possible association with day +100 MRD negativity (Table 1). There were no significant associations. Further, the incidence of acute (grade II-IV) GvHD at 100 days was not significantly different between the day 100 MRD positive und negative patients. Following factors had impact on post-transplant outcomes in multivariate analysis: presence (no vs yes) of peripheral blasts prior to allograft (OS: HR 0.3, 95% CI: 0.1-0.9, p=0.03; LFS: HR 0.4, 95% CI: 0.1-0.9, p=0.03; relapses: HR 0.4, 95% CI: 0.1-0.99, p=0.048; NRM: HR 0.5, 95% CI: 0.2-1.3, p=0.17), FLAMSA vs other preparative regimens (OS: HR 0.4, 95% CI: 0.1-0.93, p=0.03; LFS: HR 0.4, 95% CI: 0.2-0.98, p=0.04; relapses: HR 0.4, 95% CI: 0.2-1.0, p=0.05; NRM: HR 0.4, 95% CI: 0.2-1.0, p=0.06), and day +100 MRD (negative vs positive) (OS: HR 0.3, 95% CI: 0.1-0.7, p=0.009; LFS: HR 0.2, 95% CI: 0.1-0.6, p=0.001; relapses: HR 0.2, 95% CI: 0.1-0.4, p=0.0001; NRM: HR 0.2, 95% CI: 0.1-0.5, p=0.0006). Conclusions Post-transplant MRD detection plays predictive role in pre-transplant r/r AML patients and may help to define possible candidates for early post-transplant interventions. Disclosures No relevant conflicts of interest to declare.

Background The ongoing Coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is having an enormous impact on society worldwide and is especially posing a threat to health in vulnerable patients, such as patients with immune deficiencies. It is expected that patients who received Chimeric Antigen Receptor T-cell (CAR T-cell) therapy for hematologic malignancies are at risk for poor outcomes after COVID-19 due to their severely immunocompromised state caused by prior cumulative immunochemotherapy, on-target/off-tumor B-cell depletion, hypogammaglobulinemia and ongoing cytopenias. Current data are limited to small case series and case reports. This study describes the clinical characteristics and outcomes of CAR T-cell therapy recipients after developing COVID-19 in the largest cohort to date. Methods In response to the COVID-19 pandemic, the European Society for Blood and Marrow Transplantation (EBMT) developed a special COVID-19 report form to capture data from all patients with COVID-19 after treatment with CAR T-cell therapy for hematologic malignancies. Only PCR positive SARS-CoV-2 diagnosed patients before June 1 st, 2021 were included. The aim of this study was to describe the clinical course after COVID-19 diagnosis and evaluate overall survival. Overall survival probabilities were calculated using the Kaplan Meier method. Factors associated with mortality after COVID-19 diagnosis were examined using a Cox proportional hazard model. Results A total of 57 patients from 11 countries were reported to the EBMT. One patient with incomplete data at diagnosis and without any follow up information had to be excluded from the analysis. The median age of these 56 patients was 57.7 years (min-max 5.2 - 72.8) including 55 adults and one child. Of these patients, 32 were male. CAR T-cell therapy was given to 46 patients with B-cell-non-Hodgkin lymphoma, 7 patients with B-cell acute lymphoblastic leukemia, and 3 patients with multiple myeloma. The median time from CAR T-cell infusion to COVID-19 diagnosis was 7.4 months (min-max 0.03 - 25.3). At the time of COVID-19 diagnosis, 62.5% of patients were in complete remission, 12.5% of patients had a partial response and 25% of patients had relapsed/refractory disease. Forty-five patients (80%) were admitted to hospital (median 26,5 days, min-max 3-171) due to COVID-19. Of the admitted patients, 24 (53%) needed oxygen support. Twenty-two (49%) patients were admitted to the intensive care unit (median 14 days, min - max 2-65) and 16 (73%) of these patients received invasive ventilation. At the time of analysis, 25 of the 56 patients had died (44.6%), most (23/25) due to COVID-19, resulting in a COVID-19 attributable mortality rate of 41%. The Kaplan-Meier estimate of overall survival is shown in Figure 1. The median follow-up from COVID-19 diagnosis was 20.9 weeks. In 1 of the 32 alive patients there was no resolution of COVID-19 at the time of analysis. In multivariate analysis, older age (hazard ratio (HR) 1.50, 95% CI 1.11-2.03, p=0.009) and comorbidities (HR 2.56, 95% CI 1.05-6.23, p=0.001) had a negative impact on overall survival. Better performance status at time of admission (HR 0.72, 95% CI 0.59-0.88, p=0.038) had a positive impact on overall survival. Sex, time from CAR T-cell therapy to COVID-19 diagnosis, disease remission status and the occurrence of neurotoxicity or cytokine release syndrome after CAR T-cell infusion did not have a significant effect on overall survival in the multivariate analysis. Conclusion Patients with COVID-19 after B-cell-targeted CAR T-cell therapy have a very poor outcome. As it remains uncertain whether currently applied vaccination strategies against SARS-CoV-2 are effective after CAR T-cell therapy, vaccination of health-care personnel and family members in combination with protective measures against viral exposure are likely to play the most important role in protecting this vulnerable group of patients. Better treatment strategies are urgently needed. Figure 1 Figure 1. Disclosures Ljungman: OctaPharma: Other: DSMB; Enanta: Other: DSMB; Janssen: Other: Investigator; Takeda: Consultancy, Other: Endpoint committee, speaker; AiCuris: Consultancy; Merck: Other: Investigator, speaker. De La Camara: IQONE: Consultancy; Roche: Consultancy. Ortiz-Maldonado: Kite, Novartis, BMS, Janssen: Honoraria. Barba: Novartis: Honoraria; Gilead: Honoraria; BMS: Honoraria; Amgen: Honoraria; Pfizer: Honoraria. Kwon: Novartis, Celgene, Gilead, Pfizer: Consultancy, Honoraria. Sesques: Novartis: Honoraria; Chugai: Honoraria; Kite, a Gilead Company: Honoraria. Bachy: Kite, a Gilead Company: Honoraria; Novartis: Honoraria; Daiishi: Research Funding; Roche: Consultancy; Takeda: Consultancy; Incyte: Consultancy. Di Blasi: Kite, a Gilead Company: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. Thieblemont: Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Bristol Myers Squibb/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses , Research Funding; Gilead Sciences: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Cellectis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Hospira: Research Funding; Bayer: Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses . Mutsaers: BMS: Consultancy; AstraZeneca: Research Funding. Nicholson: Kite, a Gilead Company: Other: Conference fees, Speakers Bureau; Novartis: Consultancy, Other: Conference fees; BMS/Celgene: Consultancy; Pfizer: Consultancy. Martínez-López: Janssen, BMS, Novartis, Incyte, Roche, GSK, Pfizer: Consultancy; Roche, Novartis, Incyte, Astellas, BMS: Research Funding. Ribera: NOVARTIS: Consultancy, Speakers Bureau; TAKEDA: Consultancy, Research Funding, Speakers Bureau; ARIAD: Consultancy, Research Funding, Speakers Bureau; SHIRE: Consultancy, Speakers Bureau; AMGEN: Consultancy, Research Funding, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau. Sanderson: Kite, a Gilead Company: Honoraria; Novartis: Honoraria. Bloor: Kite, a Gilead Company: Honoraria; Novartis: Honoraria. Ciceri: IRCCS Ospedale San Raffaele: Current Employment. Ayuk: Novartis: Honoraria; Janssen: Honoraria; Takeda: Honoraria; Mallinckrodt/Therakos: Honoraria, Research Funding; Gilead: Honoraria; Miltenyi Biomedicine: Honoraria; Celgene/BMS: Honoraria. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Kersten: Celgene: Research Funding; Miltenyi Biotec: Consultancy, Honoraria, Other: Travel support; Roche: Consultancy, Honoraria, Other: Travel support, Research Funding; BMS/Celgene: Consultancy, Honoraria; Takeda: Research Funding; Novartis: Consultancy, Honoraria, Other: Travel support; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel support, Research Funding. Mielke: DNA Prime SA: Speakers Bureau; Immunicum: Other: Data safety monitoring board; Novartis: Speakers Bureau; Miltenyi: Other: Data safety monitoring board; Gilead/KITE: Other: Travel support, Expert panel ; Celgene/BMS: Speakers Bureau.

Introduction: Cytogenetics remains one of the most important prognostic factors in acute myeloid leukemia (AML) patients, even for outcomes after allogeneic hematopoietic cell transplantation (allo-HCT). Complex karyotype (CK) constitutes a cytogenetic category with a very adverse prognosis in this setting. However, CK is a heterogenous and loosely defined category which comprises a high diversity of cytogenetic subtypes, which is highly enriched with specific cytogenetic subtypes characterized by losses of chromosomal material at critical regions known to confer a poor prognosis per se, such as monosomal karyotype, del(7q)/-7, del(5q)/-5 or abnormalities leading to 17p region loss. On the contrary, rare AML cases characterized with only multiple numerical abnormalities known as pure hyperdiploid karyotype (HDK), have a controversial prognosis. We hypothesized that pure complex HDK AML has a distinct and much better prognosis after allo-HCT compared to non-HDK, CK AML. Methods: We selected from the EBMT registry adult patients with AML and a full cytogenetic report. HDK was defined by the presence of 49 chromosomes or more. Patients were then stratified by pure HDK (pHDK) and HDK with other cytogenetic abnormalities (HDK+), characterized by HDK and the presence of a prognostic-defining cytogenetic abnormality such as del(5q)/-5, del(7q)/-7, del(17p)/-17/i(17q), inv(3q21-26)/t(3;3)(q21;q26) or t(9;22). We included only first allo-HCT from a sibling or unrelated donor (UD) performed between 2000 and 2018. Results: A total of 236 patients were identified as having HDK. There were 95 pHDK and 141 HDK+. Median age at transplantation was 53 years (range, 18-74) and median follow-up was 43 months (range, 35-56). A diagnosis of secondary AML was reported in 48 patients (20%). At the time of allo-HCT, 180 patients (76%) were in first remission (CR1), and 56 were beyond CR1 (24%). Eighty-five (39%) patients received an allo-HCT from a sibling donor, with more matched unrelated donors (MUD) in HDK+ patients (p=0.02). Most patients (70%) had a Karnofsky performance status (KPS) score of more than 90% at the time of transplantation. A myeloablative conditioning regimen was administered in 46% of the patients. In vivo T-cell depletion was part of the regimen in 66% of the patients. The most frequent trisomies were trisomy 8, 21, 13, and 22. The 2-year probability of non-relapse mortality (NRM) was 26% for the entire cohort. The 2-year probability of LFS was 50% for pHDK and 31% for HDK+ (p=0.003). The 2-year probability of overall survival (OS) was 57% for pHDK and 36% for HDK+ (p=0.007). The 2-year cumulative incidence of relapse (RI) was 22% for pHDK and 44% for HDK+ (p=0.001) (Figure 1). The cumulative incidence of grade II-IV acute graft-versus-host disease (GvHD) and chronic GvHD was 34% and 33%, respectively, for the entire cohort. Finally, the 2-year probability of GvHD and relapse-free survival (GRFS) was 36% for pHDK and 21% for HDK+ (p=0.01). On multivariate analysis, pHDK remained associated with significantly better LFS, OS and GRFS and higher RI (all p-values Conclusions: AML with pHDK has a better outcome after allo-HCT in terms of RI, LFS, OS and GRFS. pHDK AML constitutes probably a distinct cytogenetic entity from HDK+ or other non-hyperdiploid CK AML. CK remains a strong indication for allo-HCT, but the type of abnormalities included in CK significantly influences the outcome and should guide how to manage patients after allo-HCT in terms of immunosuppression withdrawal or prophylactic/preemptive post-transplant interventions such as use of hypomethylating agents or donor lymphocyte infusions. Figure 1 Figure 1. Disclosures Labopin: Jazz Pharmaceuticals: Honoraria. Ganser: Jazz Pharmaceuticals: Honoraria; Novartis: Honoraria; Celgene: Honoraria. Socie: Alexion: Research Funding. Forcade: Novartis: Other: travel grant. Chalandon: Incyte, BMS, Pfizer, Abbie, MSD, Roche, Novartis, Gilead, Amgen, Jazz, Astra Zenec: Other: Travel EXpenses, Accomodation; Incyte, BMS, Pfizer, Abbie, MSD, Roche, Novartis, Amgen: Other: Advisory Board; Incyte: Speakers Bureau. Yakoub-Agha: Jazz Pharmaceuticals: Honoraria. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Esteve: Jazz: Consultancy; Bristol Myers Squibb/Celgene: Consultancy; Abbvie: Consultancy; Novartis: Consultancy, Research Funding; Astellas: Consultancy; Pfizer: Consultancy; Novartis: Research Funding. Mohty: Sanofi: Honoraria, Research Funding; Pfizer: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Jazz: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Gilead: Honoraria; Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria; Astellas: Honoraria; Amgen: Honoraria; Adaptive Biotechnologies: Honoraria.

Background: Treosulfan has been increasingly used in reduced toxicity regimens, especially in older or frail patients. Different doses of treosulfan plus fludarabine have shown an advantage over reduced intensity regimens, confirmed by a randomized phase 3 trial utilizing treosulfan 30 g/m² (or FT10) in the majority of patients. However, data comparing fludarabine with higher doses of treosulfan (FT14) to fludarabine combined with myeloablative doses of busulfan are limited. Aims: We compared outcomes between treatment alternatives of similar conditioning intensity: FT14 (fludarabine 150 or 160 mg/m 2 and treosulfan 42g/m 2, or FT14) over FB4 (fludarabine 150 or 160 mg/m 2 and busulfan 12.8 mg/kg). Methods: We retrospectively studied consecutive patients from the European Society for Blood and Marrow Transplantation (EBMT) registry, meeting the following inclusion criteria: a) adults diagnosed with acute myeloid leukemia (AML), b) recipients of first allogeneic hematopoietic stem cell transplantation (HSCT) from a matched unrelated or sibling donor between 2010-2020, c) HSCT at first or second complete remission (CR), d) conditioning regimen with either FT14 or FB4. Patients with ex vivo manipulated grafts were excluded. A sub-group analysis was performed according to age ( Results: In total, 2703 patients were included in the analysis comprising 2025 (75%) transplanted with FB4, and 678 (25%) with FT14. In the sub-group of patients younger than 55 years (n=1676), FT14 recipients (n=236) had a significantly increased age (p Similar differences in patient characteristics were observed in patients aged ≥55 years (n=1027). FT14 recipients (n=442) had a significantly increased age (p Conclusion: With the limitations of a retrospective analysis, our large real-world multicenter study suggests that FB4 is associated with better outcomes compared to FT14 in younger patients with AML transplanted in first or second CR. The same was not true for older patients (≥55 years). It should also be noted that FT14 has been selected by treating physicians for higher risk HSCT, including patients who are older, have secondary disease, adverse cytogenetics, and unrelated donors. Therefore, further studies are needed to determine the optimal conditioning regimen for such patient populations. Figure 1 Figure 1. Disclosures Gavriilaki: Alexion, Omeros, Sanofi Corporation: Consultancy; Gilead Corporation: Honoraria; Pfizer Corporation: Research Funding. Labopin: Jazz Pharmaceuticals: Honoraria. Yakoub-Agha: Jazz Pharmaceuticals: Honoraria. Hilgendorf: Novartis: Honoraria; AbbVie: Honoraria; Jazz Pharmaceuticals: Honoraria, Other: Travel Support; Celgene: Other: Travel Support; SanofiGenzyme: Other: Travel Support. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Mielke: Gilead/KITE: Other: Travel support, Expert panel ; Novartis: Speakers Bureau; Immunicum: Other: Data safety monitoring board; Miltenyi: Other: Data safety monitoring board; DNA Prime SA: Speakers Bureau; Celgene/BMS: Speakers Bureau. Zuckerman: AbbVie: Honoraria; Orgenesis Inc.: Honoraria; Janssen: Honoraria; BioSight Ltd: Honoraria; Novartis: Honoraria; Gilead Sciences: Honoraria, Speakers Bureau; Cellect Biotechnology: Honoraria. Giebel: Janssen: Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau. Bazarbachi: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Hikma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees. Spyridonidis: Menarini: Current Employment. Mohty: Astellas: Honoraria; Amgen: Honoraria; Celgene: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Takeda: Honoraria; Jazz: Honoraria, Research Funding; Adaptive Biotechnologies: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; Bristol Myers Squibb: Honoraria; Janssen: Honoraria, Research Funding; Gilead: Honoraria.

Background Azacitidine (Aza) in combination with donor lymphocyte infusions (DLI) is an established treatment option for pts with relapse of myeloid malignancies after allo-SCT. Accounting for its immunomodulatory and anti-leukemic properties, we considered Lenalidomide (Len) to be a synergistic partner for Aza and DLI that may further improve response rate and outcome. To investigate the tolerability and efficacy of the combination of Aza, Len and DLI as first salvage therapy for relapsed MDS, AML and CMML after allo-SCT we performed a prospective, multicenter, single-arm phase-II trial. Results from two safety interim analyses have previously been reported. Here, we report the final results from this investigator-initiated trial. Design/Methods: Patients with relapse of MDS, AML and CMML after first allo-SCT were eligible. Envisaged treatment according to the protocol consisted of up to 8 cycles Aza (75 mg/m 2/d d1-7, every 28 days) and up to 3 DLI with increasing T cell dosages (0.5×10 6 - 1.5×10 7 cells/kg). Len was administered concomitantly for 21 days of a 28-day cycle. Following a positive first interim safety analysis in 10 patients the daily dose of Len was increased from 2.5 to 5mg. The primary endpoint of the study was safety, while secondary efficacy endpoints included response type and rates, time to and duration of response and overall survival. Results: Overall, 50 pts with molecular (n=29, 58%) or hematological (n=21, 42%) relapse of MDS (n=24, 48%), AML (n=23, 46%) or CMML (n=3, 6%) detected after median of 233 days (range, 98 to 2659) after allo-SCT were included. Fourteen patients (28%) received Len at a daily dosage of 2.5 mg and 36 patients (72%) at a daily dosage of 5 mg with no DLTs observed in the interim analyses. Median number of Len cycles per patient was 7 (range, 1 to 8) with no differences between the two dose levels. Concomitantly, 34 pts (68%) received at least one DLI (median: 3, range: 1-11). Overall response rate (ORR) during treatment was 56% (CR n=25, 50%, PR n=3, 6%). ORR and CR rates did not differ between Len dose levels. Of interest, CR rate did not differ between pts treated at the stage of molecular relapse and those initiated at hematological relapse (52% vs. 48%). Median time to CR was 112 days (range 1-286) corresponding to 4 cycles (range 1 to 8). At the time of data lock, 20 patients (80%) were still in CR without additional therapy for a median of 15 months, while 5 patients (20%) had relapsed again after a median of 8 months. With a median follow-up of 20 months median OS was 21 months and 1-year OS rate 65%. While therapy-related CTC grade III/IV neutropenia (92%), thrombopenia (80%) or anemia (36%) occurred frequently, drug-related non-hematological adverse events (AE) >grade II were rare and mainly consisted of gastrointestinal toxicity (6%), laboratory findings (28%) and infections (22%). Twenty-three pts (46%) developed acute GvHD including 5 patients (10%) with grade III/IV aGvHD, and 26 pts (52%) chronic GvHD (mild n=10; moderate n=11; severe n=5). During the study period, 3 secondary malignancies (squamous cell, basal cell and vulvar carcinoma) occurred. There were no therapy related deaths. Conclusion: Len up to a dosage to 5 mg/day can be safely added to the combination of AZA and DLI without excess of GvHD and toxicity. Furthermore, these data suggest that the combination of Aza, Len and DLI has promising clinical activity for relapse of myeloid malignancies after allo-SCT and is able to induce durable responses and survival in a substantial proportion of pts. Disclosures Schroeder: Celgene: Honoraria, Other: Travel support, Research Funding. Stelljes: Kite/Gilead: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau. Holtick: Celgene: Honoraria; Sanofi: Honoraria. Germing: Janssen: Honoraria; Bristol-Myers Squibb: Honoraria, Other: advisory activity, Research Funding; Jazz Pharmaceuticals: Honoraria; Celgene: Honoraria; Novartis: Honoraria, Research Funding. Kröger: AOP Pharma: Honoraria; Celgene: Honoraria, Research Funding; Gilead/Kite: Honoraria; Jazz: Honoraria, Research Funding; Neovii: Honoraria, Research Funding; Novartis: Honoraria; Riemser: Honoraria, Research Funding; Sanofi: Honoraria. Kobbe: Celgene: Research Funding. OffLabel Disclosure: Lenalidomide is not licensed for AML, CMML and advanced MDS except for MDS with isolated del5q

IPSS-R is a well established prognostic factor for transplant outcome in patients with MDS, irrespective whether it is assessed at diagnosis or at transplant. However it is unclear how a change in IPSS-R, e.g. by reducing bone marrow blasts through therapy, would potentially affect transplant results. In particular the decision to treat patients before transplant or perform an upfront allogeneic transplantation can so far not be based on evidence. We did a registry search based in the MDS quality initiative conducted by EBMT to identify transplanted patients with MDS and sufficient data to calculate IPSS-R at diagnosis and before transplant. The search was limited to patients reveiving a first allogeneic stem cell transplantation in the period 2005 -2018. 1482 patients were identified. Median age at alloHCT was 59 (interquartile range 51-64) years, 60% were male. Donors were related in 36%, graft source was PBSC in 85% of cases. Conditioning was standard dose in 33% and reduced intensity in 67%. IPSS-R both at diagnosis and at transplant had a significant impact on OS and RFS after alloHCT. To investigate the effect of a change in IPSS-R between diagnosis and transplant we constructed 3 subgroups: stable IPSS-R, improved IPSS-R, worsened IPSS-R. A change in IPSS-R was noted in 77.5% of patients with prior chemotherapy, 72% with prior HMA and 59.8% of untreated patients. Univariate analysis showed no significant difference in OS or RFS in patients with stable IPSS-R compared to improved or worsened IPSS-R. In patients treated with chemotherapy before transplant OS and RFS was significantly worse with worsened IPSS-R, while this effect was not found in patient treated with hypomethylating agents (HMA) or untreated patients. The same analysis was performed regarding the difference in bone marrow blasts and the cytogenetics score: OS and RFS after transplant were significantly worse with increased blasts (p=0.04 and p=0.001) and a worsened cytogenetic score before transplant (both p In this retrospective analysis from a large cohort of patients with MDS we found that worsening of IPSS-R, blast count or cytogenetic score had a negative prognostic impact in chemotherapy-treated patients, while only worsened blast count and cytogenetics were significant negative factors in HMA-treated or untreated patients. Conversely we did not find a positive effect of improved IPSS-R, decreased blasts or improved cytogenetics in any of the subgroups of treated or untreated patients. Thus for MDS patients receiving an allogeneic transplantation our results provide no clear signal that prior therapy is able to improve transplant outcome. Disclosures Scheid: Novartis: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; BMS: Honoraria; Amgen: Honoraria; Takeda: Honoraria, Research Funding. Blaise:Jazz Pharmaceuticals: Honoraria. Chevallier:Incyte Corporation: Honoraria. Yakoub-Agha:Celgene: Honoraria; Novartis: Honoraria; Gilead/Kite: Honoraria, Other: travel support; Janssen: Honoraria; Jazz Pharmaceuticals: Honoraria.

Aim: Dynamic assessment of trends over time in patient- and transplant-specific characteristics and outcomes for patients undergoing 1st allogeneic haematopoietic cell transplant (allo-HCT) for Myelofibrosis (MF). Methods and Results: A total of 4142 MF patients were analysed who underwent allo-HCT between 1995-2018 (24-year period) across 278 centres based on data reported to the European Society for Blood and Marrow Transplantation. For analysis, 4 cohorts were considered based on year of allo-HCT: 60 years accounted for 8.7% of adults undergoing allo-HCT whereas for 2015-2018 this was 47%. Over time, increasing number of patients with a Karnofsky performance status (KPS) Conclusions: Despite a marked increase over this 24-year period in recipient age, RIC regimen utilisation and use of both URD and MMRD, this comprehensive analysis demonstrates stable OS and EFS rates. However, rates of GVHD have decreased over time, in particular extensive cGVHD. Further work is required to improve both the considerable NRM and relapse rates which remain significant. Disclosures McLornan: JAZZ PHARMA: Honoraria, Speakers Bureau; CELGENE: Honoraria, Speakers Bureau; NOVARTIS: Honoraria, Speakers Bureau. Platzbecker:Amgen: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Geron: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding. Chevallier:Incyte Corporation: Honoraria. Martínez-Lopez:Altum, Hosea: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Vivia Biotech: Honoraria; Amgen: Speakers Bureau; Takeda: Speakers Bureau; Roche: Speakers Bureau; Janssen: Speakers Bureau; Incyte: Research Funding, Speakers Bureau; Bristol Myers Squibb: Research Funding, Speakers Bureau; Novartis: Research Funding. Yakoub-Agha:Celgene: Honoraria; Jazz Pharmaceuticals: Honoraria; Novartis: Honoraria; Gilead/Kite: Honoraria, Other: travel support; Janssen: Honoraria.

Increased energy requirement and metabolic reprogramming are hallmarks of cancer cells. We show that metabolic alterations in hematopoietic cells are fundamental to the pathogenesis of mutant JAK2-driven myeloproliferative neoplasms (MPNs). We found that expression of mutant JAK2 augmented and subverted metabolic activity of MPN cells, resulting in systemic metabolic changes in vivo, including hypoglycemia, adipose tissue atrophy, and early mortality. Hypoglycemia in MPN mouse models correlated with hyperactive erythropoiesis and was due to a combination of elevated glycolysis and increased oxidative phosphorylation. Modulating nutrient supply through high-fat diet improved survival, whereas high-glucose diet augmented the MPN phenotype. Transcriptomic and metabolomic analyses identified numerous metabolic nodes in JAK2-mutant hematopoietic stem and progenitor cells that were altered in comparison with wild-type controls. We studied the consequences of elevated levels of Pfkfb3, a key regulatory enzyme of glycolysis, and found that pharmacological inhibition of Pfkfb3 with the small molecule 3PO reversed hypoglycemia and reduced hematopoietic manifestations of MPNs. These effects were additive with the JAK1/2 inhibitor ruxolitinib in vivo and in vitro. Inhibition of glycolysis by 3PO altered the redox homeostasis, leading to accumulation of reactive oxygen species and augmented apoptosis rate. Our findings reveal the contribution of metabolic alterations to the pathogenesis of MPNs and suggest that metabolic dependencies of mutant cells represent vulnerabilities that can be targeted for treating MPNs.

TO THE EDITOR: Age is known to be a strong negative predictor of survival in patients undergoing an allogeneic hematopoietic stem cell transplantation (HSCT) for severe acquired aplastic anemia (SAA), with higher mortality in patients >40 years of age,[1][1] and this has been confirmed in several

HSCT is the only curative option for many malignant and non-malignant diseases. The WBMT was founded as an umbrella organization of societies involved in cellular therapies with the mission of promoting excellence in HSCT. As a non-governmental organization in official relation with the World Health Organization (WHO), the WBMT assisted in the founding of regional societies (Latin America Blood and Marrow Transplantation Group and African Blood and Marrow Transplantation Group), performs global activity surveys, conducts workshops and provides expert support for programs in evolving countries. In this retrospective evaluation we analyzed worldwide activity trends in HSCT up to the year 2016 and evaluated possibilities of improving availability of HSCT by the use of telemedicine. Methods: HSCT activity was collected annually from member societies, national registries and individual centers including donor type (allogeneic/autologous), stem cell source (bone marrow/peripheral blood stem cells/cord blood) and indications for transplant. Transplant rates (TR) were calculated as HSCT/10 million inhabitants without adjustment for patients transplanted in a country other than that of primary residence. Country team density (TD) was defined as teams/10 million inhabitants. Workshops were organized in a number of locations where there was little or no HSCT activity or where improvement in one or more aspect of local or regional HSCT activity was requested, including Vietnam, Brazil, China, South Africa and Morocco. Other countries were paired with established centers using WBMT affiliated partners. In two countries, a pilot program was established involving a 6 month physician training in a JACIE/FACT accredited center followed by daily telemedicine-guided supervision of clinical activities. Results: From 1957-2016 a total of 1,298,897 HSCT (57.1% autologous) procedures were collected. By the end of 2016, HSCT activity was reported from 87 of the 195 WHO member states. A total of 89,070 HSCT from 1662 centers was reported in 2016. Assuming a frequency of 84,000/year, 1.5 million HSCT will be reached in 2019, only 7 years after the 1 million report in 2012 (Figure 1). The global activity/year increased continuously from 10,000/year in 1991 to 82,718 first HSCT/year in 2016 with a global increase of >7% (7.0% in autologous and 7.8% in allogeneic HSCT). As in previous years, slightly more autologous (53.5%) than allogeneic and more related (53,6%) than unrelated HSCT were reported. The further increase in related HSCT was caused mainly by an increase of non-identical family donors (39.5% of related HSCT). Increase in activities according to regions is given in Figure 2. TR and TD varied according to region and are highest in Nord America with 511.2 TR, followed by Europe with 390.9 TR, Latin America with 63.9 TR, APBMT with 46.2 TR and Africa/EMRO with 32.8 TR. In contrast, TD was highest in Europe (7.5 TD) followed by Nord America (6.0 TD), APBMT (1.9 TD), Latin America (1.9 TD) and Africa/EMRO (0.4 TD). Commonest indications were lymphoproliferative diseases for autologous and leukemia for allogeneic HSCT and continue to rise (Figure 3 autologous and Figure 4 allogeneic HSCT). Graft source were predominantly peripheral blood in autologous (99.7%) and 65% in unrelated HSCT, while umbilical cord blood as a stem cell source (13.8% of all unrelated) declined. More than 150 HSCT were performed in one country and one center without activities using daily telemedicine-guided supervision. In conclusion, the global distribution and activities are increasing continuously by more than 7,0% per year with numbers currently running at app. 90,000/year. Of note is the increase of haploidentical HSCT activity, while the use of umbilical cord blood HSCT continues to decrease. TR data show significant gaps between regions. Supervisory telemedicine is a powerful tool to overcome lack of experience and establish JACIE/FACT compatible new programs with collateral benefits for conventional hematology, blood banking, microbiology and virology. Abbreviations: EUR, Europe; AMR/PHA, America; SEAR/WPR, South-East Asia/Western Pacific; AFR/EMRO, African/Eastern Mediterranean. Disclosures Niederwieser: Daichii: Speakers Bureau; Cellectis: Consultancy. Atsuta:Kyowa Kirin Co., Ltd: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria; Mochida Pharmaceutical Co. Ltd: Honoraria; Janssen Paharmaceutical K.K.: Honoraria. Worel:Sanofi Genzyme, Malinckrodt Therakos: Research Funding; Jazz, Sanofi, Celgene, Novartis, Malinckrodt Therakos: Honoraria; Sanofi Genzyme, Malinckrodt Therakos: Speakers Bureau. Galeano:Szabo SA: Other: (Equity interest). Novitzky:Astellas, Roche: Consultancy. Szer:Prevail Therapeutics: Honoraria, Other: Travel, Research Funding; Novartis: Honoraria, Other: Travel, Research Funding; MSD: Honoraria, Other: Travel, Research Funding; Celgene: Honoraria, Other: Travel, Research Funding; Amgen: Honoraria, Other: Travel, Research Funding; Alexion: Honoraria, Other: Travel, Research Funding; Sanofi: Honoraria, Other: Travel, Research Funding; Takeda: Honoraria, Other: Travel, Research Funding; Pfizer: Honoraria, Other: Travel, Research Funding. Kröger:Celgene: Honoraria, Research Funding; DKMS: Research Funding; JAZZ: Honoraria; Medac: Honoraria; Neovii: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Riemser: Research Funding; Sanofi-Aventis: Research Funding. Weisdorf:Incyte: Research Funding; Pharmacyclics: Consultancy; Fate Therapeutics: Consultancy. Pasquini:Amgen: Consultancy; BMS: Research Funding; Medigene: Consultancy; Pfizer: Other: Advisory Board; Novartis: Research Funding; Kit Pharma: Research Funding.

Thanks to the recent developments in transplant procedures, an increasing number of patients with acute myeloid leukemia (AML) with a poor Karnofsky Performance Status (KPS) score are currently offered an allogeneic hematopoietic stem cell transplantation (allo-HCT). Nevertheless, little data is available about outcome of this fragile population. We report here the results of a retrospective study designed to evaluate outcome of patients with AML undergoing allo-HCT with KPS score ≤80%. The analysis included patients with AML aged ≥18 years, undergoing allo-HCT in first remission between 2000 and 2018, with a KPS score at the time of transplant between 50% and 80%. Patients who received manipulated grafts or had incomplete data about cytogenetics were excluded. Conditioning intensity was defined according to EBMT definitions. A total of 2,963 patients were identified. Median age at transplant was 55 years (18-77 years). Median year of transplant was 2014. The KPS score was =80% in 85% of the patients and Cumulative incidence of grade II-IV and III-IV acute GVHD (aGvHD) was 26% and 8%, respectively. The 2-year cumulative incidence of chronic GVHD (cGvHD) and severe cGVHD was 38% and 18%. Non-relapse mortality (NRM) and relapse incidence (RI) at 2 years were 19% and 27%, respectively. Notably, in the subgroup of patients with KPS On multivariate analysis, transplant from a MSD was associated with a reduced risk of aGvHD (10/10 UD HR 1.8, 9/10 UD HR 2.4, haplo HR 1.9, CB HR 3.4, p In order to compare outcome following MAC and RIC conditioning the analysis was restricted to patients receiving transplant from MSD or UD. Patients with a KPS score =80% or In conclusion, allo-HCT is feasible in patients with acute myeloid leukemia in first remission and KPS score Disclosures Labopin: Jazz Pharmaceuticals: Honoraria. Kröger:Sanofi-Aventis: Research Funding; Celgene: Honoraria, Research Funding; DKMS: Research Funding; JAZZ: Honoraria; Medac: Honoraria; Neovii: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Riemser: Research Funding. Socie:Alexion: Consultancy. Blaise:Pierre Fabre medicaments: Honoraria; Jazz Pharmaceuticals: Honoraria; Sanofi: Honoraria; Molmed: Consultancy, Honoraria. Byrne:Ariad/Incyte: Honoraria, Speakers Bureau. Esteve:Astellas: Consultancy, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Amgen: Consultancy; Daiichi Sankyo: Consultancy; Jazz Pharmaceuticals: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Mohty:Jazz Pharmaceuticals: Honoraria, Research Funding.

Introduction: Complex aberrant karyotypes (CK, ≥3 cytogenetic aberrations, CA) are associated with an unfavorable prognosis and an increased AML transformation rate in MDS. However, even MDS with CK (CK-MDS) are heterogeneous in terms of genetic profile and prognosis. Recently, we demonstrated that a high number of CA as well as mutations in TP53 (TP53mut) are associated with increased risk in CK-MDS (Haase et al, 2019). However, as there is a strong association between CK-MDS and TP53mut, it is still a matter of debate whether the karyotype and TP53mut are prognostically independent genetic markers. Furthermore, loss of heterozygosity (LOH) of 17p13 (TP53LOH), due to loss of genetic material or to copy number neutral LOH (CN-LOH), is also associated with a poor prognosis. We here aimed to characterize TP53mut andTP53LOH in CK-MDS and to elucidate the impact of cytogenetics, TP53mut and TP53LOH on the outcome of CK-MDS. Methods: We included 178 pts with MDS (N=138), CMML (N=5) and secondary AML after MDS (AML with myelodysplasia-related changes, N=35), all with CK. The median precentage of bone marrow (bm) blasts was 11% (range: 0-90%). The median age was 72 yrs (range: 30-95 yrs). The male:female ratio was 1.23:1. The number of CA was determined by banding analysis in all cases. The karyotype was confirmed by multicolor FISH in 134 cases. TP53LOH was verified by FISH analysis of the TP53 locus in 17p13 (146 analyses) and/or molecular karyotyping (MK, 41 analyses). In 144 cases further FISH probes in addition to TP53 were used. TP53mut was identified by NGS (54 cases) or Sanger sequencing (124 cases). Follow-up data for survival analyses were available for 127 pts with MDS and oligoblastic AML with less than 30% bm blasts. Results: The median number of CA was 7 (range: 3-46), 98/178 pts (55%) showed a TP53mut (median VAF: 34%, range: 8-93%) and 64/178 (36%) a TP53LOH (median FISH clone size: 65%, range: 6-99%), including 9 pts with a CN-LOH in 17p13. The CN-LOH was either identified by MK (5/41 pts (12%) where MK was available showed a CN-LOH, 4/5 with TP53mut) or by NGS (4/54 pts (7%) where NGS was available showed a VAF >70% and normal TP53-FISH). In total, a TP53mut and/or a TP53LOH was identified in 116/178 pts (65%). Overall survival (OS) did not significantly differ between CK-MDS with TP53mut only, TP53LOH only, and TP53mut+TP53LOH (Fig.1). Therefore, we merged TP53mut and TP53LOH to TP53altered in all further analyses. Regarding the cytogenetic characterization of pts with TP53altered, the number of CA was significantly higher in pts with TP53altered than in pts with normal TP53 (median 9 CA (range: 3-46) vs 5 CA (range: 3-24), P The number of CA as well as the TP53 status contributed significantly to OS (Fig.2). The presence of anemia (Hb Conclusions: The presence of ≥5 CA is associated with reduced OS in CK-MDS. A TP53mut as well as a TP53LOH both further segregate outcome. The impact of the clone size of TP53mut and TP53LOH on survival is currently being evaluated. Our data imply that the TP53 status (TP53mut and/or TP53LOH) and the complexity of the karyotype are independent prognostic markers. Based on the presence of anemia, the TP53 status (TP53mut and/or TP53LOH), and the number of CA, the individual risk of CK-MDS can be estimated more accurately. This will allow to better tailor treatment decisions for individual pts with CA. Funding (FS): 2017 SGR 288-GRC Disclosures Germing: Jazz Pharmaceuticals: Honoraria; Novartis: Honoraria, Research Funding; Amgen: Honoraria; Celgene: Honoraria, Research Funding. Kaivers:Jazz Pharmaceuticals: Other: Travel Support. Kröger:Celgene: Honoraria, Research Funding; DKMS: Research Funding; JAZZ: Honoraria; Medac: Honoraria; Neovii: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Riemser: Research Funding; Sanofi-Aventis: Research Funding. Hertenstein:RS Media: Research Funding. Döhner:Daiichi: Honoraria; Jazz: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Janssen: Honoraria; CTI Biopharma: Consultancy, Honoraria. Bug:Hexal: Membership on an entity's Board of Directors or advisory committees; Celgene Neovii: Other: travel grant; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Other: Travel grants; Sanofi: Other: travel grants; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; Jazz Pharmaceuticals: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees. Nickelsen:Roche Pharma AG: Membership on an entity's Board of Directors or advisory committees, Other: Travel Grants; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant; Janssen: Membership on an entity's Board of Directors or advisory committees. Platzbecker:Celgene: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.

Recently, an increasing number of patients with acute lymphoblastic leukemia with a poor Karnofsky Performance Status (KPS) score are considered for allogeneic hematopoietic stem cell transplantation (allo-HCT). Nevertheless, there is paucity of available data about outcome of this fragile population. We report here the results of a retrospective study designed to evaluate outcome of ALL patients undergoing allo-HCT with KPS score ≤80%. 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). 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 On multivariate analysis, transplant from 10/10 UD was associated with higher incidence of aGVHD (HR 1.8, p 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. Disclosures Labopin: Jazz Pharmaceuticals: Honoraria. Socie:Alexion: Consultancy. Kröger:JAZZ: Honoraria; Medac: Honoraria; Neovii: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Riemser: Research Funding; Sanofi-Aventis: Research Funding; Celgene: Honoraria, Research Funding; DKMS: Research Funding. Mohty:Jazz Pharmaceuticals: Honoraria, Research Funding.

Background: Haploidentical stem cell transplantation (Haplo HSCT) has emerged in the past three decades as an alternative curative option when an HLA match donor is not available. Over time, the use of Haplo has increased dramatically, reaching superimposable results when compared to unrelated and related HSCT strategies, confirming its validity. The widespread use of Haplo mainly relies upon technical advances, control of alloreactivity through graft-versus-host disease (GvHD) prophylaxis combined with a rapid and almost universal probability to find an Haplo donor for any candidate patient. The aim of our study was to provide a picture of acute (aGvHD) and chronic GvHD (cGvHD) incidence in Haplo HSCT across different platform in the past 15 years, where Haplo moved from ex-vivo T-cell depleted (TCD) platform to in-vivo TCD platform to the post-transplantation cyclophosphamide (PTCy). Methods: We compared the outcomes of adult patients receiving a 1st Haplo HSCT for any hematological malignancy according to GvHD prophylaxis - ex-vivo + in-vivo TCD (n=160), in-vivo only TCD (n=507) or PTCy (n=2593) - and reported to the EBMT registry in 2004-2016. Patients with missing data on disease status at last follow-up and GvHD information were excluded. Primary endpoint was GvHD-free & Relapse-free survival (GRFS) with events defined by death or relapse or grade ≥3 aGvHD or extensive (ext) cGvHD. Secondary endpoints were progression-free survival (PFS), overall survival (OS), aGvHD and cGvHD, incidence of relapse (IR) and non-relapse-mortality (NRM). Due to sample size in the first cohort of ex-vivo TCD, multivariate analysis compared only in-vivo TCD vs PTCy cohorts. Table 1 illustrates patients' characteristics. Results: Univariate analysis for 3-year outcomes are reported on table 2. PTCy provides better GRFS, OS, PFS, NRM versus ex-vivo or in-vivo. IR was not significantly different. Likewise, the 3-year CI of cGvHD and ext cGvHD were similar between PTCy, in vivo TCD and ex-vivo TCD (cGvHD 27% [25-29%], 25% [21-29%], 18% [12-25%], p 0.03; ext cGvHD 11% [10-12%], 10% [8-13%], 8% [4-13%], p 0.45). On the contrary the 100-day CI of grade ≥2 aGvHD were lower in the ex-vivo TCD vs PTCy and in-vivo TCD (19% [14-26%], 28% [26-30%], 32% [28-36%], p 0.002) while grade ≥3 aGvHD were lower in the PTCy group vs ex-vivo and in-vivo TCD (9% [8-10%], 11% [7-17%], 14% [11-18%], p After adjustment for diagnosis, patient age, disease status, Karnofsky PS, donor/patient gender and CMV, cell source, conditioning intensity, previous auto and year of transplant, the multivariable model comparing in-vivo TCD and PTCy showed better outcome for PTCy. Compared to in-vivo TCD, the hazards for GRFS was 0.76 for PTCy (p 0.004), the HR for PFS was 0.71 (p 0.001) and the HR for OS was 0.7 (p 0.0008), the HR for NRM was 0.63 (p 0.001). Moreover, compared to in-vivo TCD, PTCy yielded similar hazards for grade≥2 aGvHD (HR: 1.02, p 0.89), grade≥3 aGvHD (HR 0.79, p 0.27), cGvHD (HR 1.17, p 0.37), ext cGvHD (HR 1.18, p 0.52) and relapse (HR 0.8, p 0.1). Variables associated with GRFS were active disease, Karnofsky PS ≥90%, diagnosis, donor/patient gender and CMV. An ancillary analysis evaluating the stem cell source effect in the PTCy cohort only, demonstrates comparable outcome endpoints (OS, PFS, NRM, IR) at 2-year between bone marrow (BM) and peripheral blood (PB) PTCy. In univariate analysis GRFS and the 2-year CI of cGvHD were not different between BM and PB (GRFS 47% [45-50%], 46% [44-49%], p 0.085; 2-year CI of cGvHD 25% [23-28%], 27% [25-30%], p 0.2) while ext cGvHD, 100-day CI of grade ≥2 aGvHD and grade ≥3 aGvHD were lower in BM PTCy vs PB PTCy (ext cGvHD 8% [7-10%], 12% [10-14%], p Compared to BM PTCy, the HR for cGvHD was 1.55 for PB PTCy (p 0.001), the HR for ext cGvHD was 2.04 (p 0.0003), the HR for grade ≥2 aGvHD was 1,94 (p Conclusions: In the present EBMT registry study on more than 3000 patients transplanted from an Haplo donor, we report improved outcome (better GRFS - in spite of comparable chronic GvHD - OS and PFS, lower NRM) and widespread use in different diagnosis setting other than acute leukemia in PTCy platform. PTCy strategy provides a concrete progress into the field: even if cGvHD still represent a major issue, exploitation of BM PTCy seems to protect against most severe GvHD manifestation. Disclosures Mohty: Jazz Pharmaceuticals: Honoraria, Research Funding. Kröger:Sanofi-Aventis: Honoraria; Riemser: Research Funding; Novartis: Honoraria, Research Funding; Neovii: Honoraria, Research Funding; Medac: Honoraria; JAZZ: Honoraria; DKMS: Research Funding; Celgene: Honoraria, Research Funding. Basak:Celgene: Honoraria; Teva: Honoraria.

Introduction Although many new drugs became available to treat multiple myeloma (MM), high-dose chemotherapy with auto-HCT remains the gold standard. Further intensification to improve disease control has been assessed in several trials. However, no clear consensus has emerged. Further evidence is therefore required to guide clinicians in choosing between single auto, tandem auto and auto-allo approaches. Materials and Methods We performed a retrospective analysis of MM patients (20-65 years) undergoing their first auto-HCT in EBMT centres (2002-2015). Our primary end-points were Progression-Free Survival (PFS) and Overall Survival (OS). We used 3 different statistical methods to avoid time bias and to account for time-dependent effects. We defined tandem transplants (auto-auto2 or auto-allo) given within 9 months in absence of progression. Single- and tandem-transplant groups were compared by a landmark analysis (1). In addition, two different dynamic prediction models (2, 3) were applied to predict long-term outcomes in all patients according to the treatment actually received while avoiding the loss of information that occurs in landmark analysis. The models incorporated a horizon time of 5 years for OS and PFS during the first 3 years following auto1. Since the effects of tandem transplants vary over time, these were split into "Recent", the first 100 days following the 2nd transplant, and "Past" for the longer term (2, 3), respectively. Age, disease status and calendar year of transplant at auto1 were also analysed. Furthermore, the third model incorporated the long-term time-varying effect of auto-allo or auto-auto2 and possible associated interactions with patients' characteristics. Results A total of 24,936 patients who received an auto as first transplant were included; 3,683 of these patients proceeded to an elective tandem auto and 878 to an auto-allo transplant. The median age of the entire cohort was 57.0 years (range 18.1.-65.0). 18% were in complete remission (CR) at first auto. The Tandem auto-allo group was younger (51.7 years). Both tandem groups (auto-auto and auto-allo) had fewer patients in CR at first auto (9% and 8%, respectively). There was no difference in CR rates at second transplant in the tandem groups (18% and 19%, respectively). In the tandem auto-allo group, 72% had HLA identical sibling donors and 25% matched unrelated donors. Reduced intensity conditioning was performed in 85% of the allogeneic transplants. The median follow-up of the entire cohort was 66.3 months. At 60 months following first auto, the PFS was 24.8% and OS 63.1%. All three statistical methods found that younger age and being in CR at first transplant were associated with superior PFS and OS. The long term results of the different transplant strategies were as follows: Landmark analysis at 4 months resulted in a reduction in the number of transplants analysed. Auto-allo only had an advantage in terms of very long term PFS (figure 1) and not for OS (not shown).Dynamic prediction (table 1, curves not shown) revealed that the tandem groups were superior regarding PFS in comparison to single auto (auto-allo and auto-auto: HR 0.56 and 0.85, both p Summary We here present a very large cohort of patients who have undergone auto and allo transplantation as first-line treatment for MM. Younger age and being in CR at first transplant were consistently found to be positive prognostic factors for PFS and OS. Tandem auto-allo was superior to single and tandem auto for long-term PFS. However, this PFS advantage only translated into a minor OS benefit for tandem auto-allo even when analysis was restricted to patients who were not in CR at the time of the first auto-HCT. Disclosures Schönland: Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Medac: Other: Travel Grant. Blaise:Pierre Fabre medicaments: Honoraria; Sanofi: Honoraria; Jazz Pharmaceuticals: Honoraria; Molmed: Consultancy, Honoraria. Chevallier:Jazz Pharmaceuticals: Honoraria; Daiichi Sankyo: Honoraria; Incyte: Consultancy, Honoraria. Mayer:AOP Orphan Pharmaceuticals AG: Research Funding. Gribben:Abbvie: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Acerta/Astra Zeneca: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Stelljes:MDS: Consultancy; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Honoraria; Amgen: Honoraria; Jazz Pharmaceuticals: Honoraria. Bloor:Abvie, Gilead, Novartis, Autolus, Celgene, etc: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational grant. Beksac:Celgene: Speakers Bureau; Janssen: Research Funding, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hayden:Amgen: Honoraria; Alnylam: Honoraria. Kröger:Celgene: Honoraria, Research Funding; DKMS: Research Funding; JAZZ: Honoraria; Medac: Honoraria; Neovii: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Riemser: Research Funding; Sanofi-Aventis: Research Funding.

Introduction Myeloproliferative Neoplasm (MPN) unclassifiable (MPN-U), is a heterogeneous disease that presents with an MPN-type clinical/ histological phenotype yet fails to meet diagnostic criteria for other MPN entities. Incidence is Methods This registry-based analysis was approved by the Chronic Malignancies Working Party of the EBMT. Patient selection was performed by identifying adult patients who underwent first allo-HCT for MPN-U between 2000-2015, using either Reduced Intensity Conditioning (RIC) or Myeloablative conditioning (MAC) as defined by standard EBMT criteria. Further data collection requests (MED-C) forms were sent to centres to improve data completeness. Statistical analyses were performed with SPSS 22 (SPSS Inc./IBM, Armonk, NY) and R. Overall Survival (OS) was calculated from the date of transplant until death or last observation alive. Cumulative incidence functions were used to estimate Non-Relapse Mortality (NRM) and Relapse Incidence (RI) within a competing risk setting. Results A total of 70 patients, 48 (69%) male and 22 (31%) female, with a confirmed diagnosis of MPN-U were analysed. Median age was 57 years (range (r), 22-70 years). Of these patients, 37 (53%) underwent allo-HCT in the period 2001-2010 and 33 (47%) between 2011-2015. MAC regimens were utilised in 31 (44%) patients while 39 (56%) received RIC. Patients were most frequently transplanted within the first two years from diagnosis, with a median time to allo-HCT of 13 months (r, 3-244 months). Diagnostic karyotype was normal in 36 (51%) and abnormal in 23 (33%) patients, with data missing for 11 (16%) patients. A total of 45 (64%) patients had received prior treatment, 23 (33%) patients were untreated and data was incomplete in 2 (3%) patients. Regarding donor type, 27 (39%) patients had a Matched Sibling Donor (MSD) and 43 (61%) an Unrelated Donor (URD). Most frequent conditioning regimens were TBI-based in the MAC cohort and Fludarabine-Busulphan in the RIC cohort. A trend towards higher rates of delayed/failed engraftment was noted in the RIC compared to MAC cohort (p=0.09). Where successful, median time to neutrophil engraftment in both cohorts was similar (18 days for MAC and 17 for RIC) and both platforms demonstrated similar platelet engraftment times (17.5 days). Incidence of grade II-IV aGVHD at 3 months was higher in the MAC (37%) compared to RIC cohort (16%; p=0.05) and the 12-month cumulative incidence of cGVHD for MAC was 52% (95%CI: 32.4, 71.6) and for RIC 32.1% (95%CI: 14.8, 49.4; p=0.117)). Median follow-up was 87 months (minimum and maximum of censored cases: 31 and 196 months). The median OS estimates at 1, 3 and 5-year were 77%, 55% and 42% (MAC) and 59%, 44% and 41% (RIC), respectively (p=0.33). No significant difference existed in OS rates between those who had pre-transplant therapy versus not. Relapse remained significant: cumulative incidences of relapse at 1,3 and 5-years were 10%, 23% and 27% (MAC) and 28%, 36% and 36% (RIC), respectively (p=0.28). NRM probabilities at 1, 3 and 5-years post allo-HCT were also considerable: 19%, 29%, and 34% (MAC) and 28%, 28% and 28% (RIC), respectively (p=0.84). Main causes of NRM were infection and GVHD. Univariate analysis associated use of an URD with a significantly worse OS and NRM compared with MSD. Moreover, the presence of abnormal karyotype at time of allo-HCT was associated with a trend towards a higher risk of relapse (p=0.06). Conclusions This study highlights the potentially curative role of allo-HCT in MPN-U and provides clinicians with robust engraftment, GVHD and outcome data. Both engraftment and OS rates appear acceptable yet NRM and CIR rates in both settings remain high and need to be addressed. The impact of abnormal karyotype at the time of allo-HCT and a trend towards higher risks of relapse requires further elucidation. Disclosures McLornan: Novartis: Honoraria; Jazz Pharmaceuticals: Honoraria, Speakers Bureau. Robin:Novartis Neovii: Research Funding. Chalandon:Novartis: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Incyte Biosciences: Consultancy, Honoraria. Beelen:Medac GmbH Wedel Germany: Consultancy, Honoraria. Kröger:Sanofi-Aventis: Honoraria; Riemser: Research Funding; Novartis: Honoraria, Research Funding; Neovii: Honoraria, Research Funding; Medac: Honoraria; JAZZ: Honoraria; DKMS: Research Funding; Celgene: Honoraria, Research Funding. Milojkovic:Novartis: Honoraria, Speakers Bureau; Incyte: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau. Hernandez Boluda:Incyte: Other: Travel expenses paid.

Introduction: The only curative treatment for myelofibrosis (MF) remains allogenic haematopoietic cell transplantation (allo-HCT) although the risks of non-relapse mortality (NRM), relapse and graft rejection need to be taken into consideration. Therapeutic approaches following relapse after allo-HCT include symptom-directed management, chemotherapy, JAK2 inhibitors, adoptive immunotherapeutic approaches with donor lymphocyte infusion (DLI) and, in a minority, a second allo-HCT. Frequently, due to the advanced age of the recipient, early relapses, and numerous complications, 2nd allo-HCT can only be considered in a limited number of patients. Few studies evaluating the role of 2nd allo-HCT in MF following 1st relapse or primary/secondary graft rejection have been published to date. Methods and results: Patient selection was performed by identifying adult patients who underwent 2nd allo-HCT for MF between 2010-2017: 216 patients were analyzed; 64% were male, 78% had primary MF (PMF) and 22% secondary MF (sMF). Median age at the time of 2nd allo-HCT was 57 years, and median time from 1st allo-HCT was 8 months. Of this cohort, 56% of patients received a 2nd allo-HCT for relapse, 31% for graft failure and the reason was missing in 13%. A greater proportion was transplanted within 1 year from 1st allo-HCT (61 %) whilst 39% had 2nd allo-HCT > 1 year. A reduced Karnofsky performance status (KPS12 months, p=0.02). The 2-year relapse-free-survival (RFS) for the entire cohort was 44%. Only time elapsed from the 1st allo-HCT to 2nd was significantly associated with 2-year RFS (41% for ≤12 months, 49% for >12 months, p=0.05). Of note, the 2-year OS and RFS were comparable following use of the same or a different donor. The 2-year cumulative incidence of relapse and NRM were 22 and 34%, respectively. The time interval from 1st to 2nd allo-HCT appeared to be highly significant for NRM with patients transplanted ≤12 months having a higher 2-year NRM compared to those transplanted >12 months (40 vs 24%, respectively, p=0.008). A trend for higher NRM was the reason for 2nd allo-HCT: patients transplanted for graft rejection had a 2-year NRM of 45% compared to 31% for those with relapse (p=0.06). Conclusions: This analysis supports the utilization of a 2nd allo-HCT for patients with MF who have presented with graft failure or relapse following a 1st allo-HCT. In univariate analysis, overall outcome appears worse in patients being transplanted after graft failure as well as for those transplanted within 1 year after 1st allo-HCT, due to increased NRM. Of note, the use of either the original or a different donor are associated with similar outcomes. Further work is required to elucidate other risk factors, GVHD rates and to define the optimal conditioning regimen in this setting. Table. Disclosures Robin: Novartis Neovii: Research Funding. Kröger:Sanofi-Aventis: Honoraria; Riemser: Research Funding; Novartis: Honoraria, Research Funding; Neovii: Honoraria, Research Funding; Medac: Honoraria; JAZZ: Honoraria; DKMS: Research Funding; Celgene: Honoraria, Research Funding. Angelucci:Celgene: Honoraria, Other: Participation in DMC; BlueBirdBio: Other: Local advisory board; Jazz Pharmaceuticals: Other: Local advisory board; Roche: Other: Local advisory board; Vertex Pharmaceuticals Incorp., and CRISPR Therapeutics: Other: Participation in DMC; Novatis: Honoraria, Other: Chair Steering Committee TELESTO protocol. Dreger:AbbVie, AstraZeneca, Gilead, Janssen, Novartis, Riemser, Roche: Consultancy; AbbVie, Gilead, Novartis, Riemser, Roche: Speakers Bureau; MSD: Membership on an entity's Board of Directors or advisory committees, Other: Sponsoring of Symposia; Neovii, Riemser: Research Funding. Platzbecker:Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. Rambaldi:Novartis: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding, Speakers Bureau; Italfarmaco: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: travel support, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Omeros: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Mayer:AOP Orphan Pharmaceuticals AG: Research Funding. Ladetto:ADC Therapeutics: Honoraria; Pfizer: Honoraria, Speakers Bureau; Celgene: Honoraria; J&J: Honoraria; Roche: Honoraria; AbbVie: Honoraria; Acerta: Honoraria, Speakers Bureau. Hernandez Boluda:Incyte: Other: Travel expenses paid. McLornan:Jazz Pharmaceuticals: Honoraria, Speakers Bureau; Novartis: Honoraria. Chalandon:Incyte Biosciences: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

We analyzed the prognostic impact of donor and recipient cytomegalovirus (CMV) serostatus in 16,628 de novo acute leukemia patients after allogeneic stem cell transplantation (allo-SCT). Compared with CMV-seronegative recipients who underwent allograft from a CMV-seronegative donor, cases of CMV seropositivity of the donor and/or the recipient showed a significantly decreased 2-year leukemia-free survival (44% vs 49%, P < .001) and overall survival (50% vs 56%, P < .001), and increased nonrelapse mortality (23% vs 20%, P < .001). Both groups showed a comparable relapse incidence and 2-year probability of graft-versus-host disease. The negative prognostic effects of CMV seropositivity of the donor and/or the recipient (vs CMV seronegativity of both) were significantly stronger for acute lymphoblastic leukemia (ALL) than for acute myeloid leukemia (AML), resulting in a markedly reduced 2-year overall survival (46% vs 55% for ALL compared with 52% vs 56% for AML). The important prognostic impact of donor/recipient CMV serostatus remained in a multivariate Cox regression analysis including the other prognostic variables. We conclude that donor and/or recipient CMV seropositivity is still associated with an adverse prognosis in de novo acute leukemia patients after allo-SCT despite the implementation of sophisticated strategies for prophylaxis, monitoring, and (preemptive) treatment of CMV.

The current document is a revision of the International Working Group-Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) criteria for treatment response in myelofibrosis (MF) and represents a collaborative effort by the IWG-MRT and the European LeukemiaNet to objectively assess the value of new drugs in inducing morphologic remission or improvement in MF-associated symptomatic burden (MF-SB). Some of the changes in the current revision include stricter definitions of red cell transfusion dependency and independency and consideration of the Myeloproliferative Neoplasm Symptom Assessment Form as a tool to quantify meaningful changes in disease-related symptoms. Six response categories are listed: complete remission (CR) and partial remission signify treatment effects that are consistent with disease modification, whereas drug-induced improvements in MF-SB were annotated as clinical improvement, anemia response, spleen response, or symptoms response. Additional criteria are provided for progressive disease, stable disease, and relapse. The document also includes recommendations for assessing cytogenetic and molecular remissions, without mandating their inclusion for CR assignment.

Lymphocyte depletion with antithymocyte globulin (ATG) can be complicated by systemic coagulation activation. We found that ATG activated tissue factor procoagulant activity (TF PCA) on monocytic cells more potently than other stimuli that decrypt TF, including cell disruption, TF pathway inhibitor inhibition, and calcium ionophore treatment. Induction of TF PCA by ATG was dependent on lipid raft integrity and complement activation. We showed that ATG-mediated TF activation required complement activation until assembly of the C5b-7 membrane insertion complex, but not lytic pore formation by the membrane attack complex C5b-9. Consistently, induction of TF PCA by ATG did not require maximal phosphatidylserine membrane exposure and was not correlated with the magnitude of complement-induced lytic cell injury. Blockade of free thiols, an inhibitory monoclonal antibody to protein disulfide isomerase (PDI), and the small-molecule PDI antagonist quercetin-3-rutinoside prevented ATG-mediated TF activation, and C5 complement activation resulted in oxidation of cell surface PDI. This rapid and potent mechanism of cellular TF activation represents a novel connection between the complement system and cell surface PDI-mediated thiol-disulfide exchange. Delineation of this clinically relevant mechanism of activation of the extrinsic coagulation pathway during immunosuppressive therapy with ATG may have broader implications for vascular thrombosis associated with inflammatory disorders.