GVHD-free/relapse-free Survival Research Articles

UM171 Expanded Cord Blood Transplantation Outcomes Compare Favorably to All Different Stem Cell Sources: An EBMT Registry Case-Control Analysis

Background: Cord blood (CB) transplantation (CBT) has several advantages compared with other graft sources, such as permissive human leucocyte antigen (HLA) mismatches, and low risk of chronic graft-versus-host disease (GVHD) and relapse. However, CBT has fallen into disfavor because of its high risk of non-relapse mortality (NRM) and prolonged hospitalization due to its low cell dose. Furthermore, the need for the rare large cord bloods (CBs) leads to selection of poorly HLA-matched CBs, known to further increase NRM. UM171 is a small molecule that expands hematopoietic stem cells. A phase I-II study of a single UM171-expanded, myeloablative and reduced intensity CBT for patients with high-risk hematologic malignancies who lacked a donor, demonstrated prompt neutrophil engraftment, the ability to use smaller, better HLA-matched CBs, and a low NRM of 5% (Cohen S et al. Lancet Haematol 2020). The aim of the current analysis was to compare outcomes after a UM171 CBT to real-world cohorts of 6 other stem cell sources identified in the European Society for Blood and Marrow Transplantation (EBMT) registry. Methods: This is a retrospective study comparing 22 adults who received a single UM171-expanded CBT in the phase I-II study between 2016-2018, to 6 cohorts of patients allografted from different stem cell sources and reported to the EBMT registry. Control patients were eligible if they had received a myeloablative or reduced intensity allogeneic transplant for a hematologic malignancy in Europe during 2010-2021, were between the ages of 18-65 years, and had a Karnofsky performance status (KPS) score ≥70. The different donor control cohorts were: 1) CB, single or double units, with a calcineurin inhibitor (CNI) and mycophenolate mofetil (MMF) for GVHD prophylaxis, 2) 10/10 HLA-matched unrelated donor (MUD) peripheral blood stem cells (PBSC) with a CNI and MMF or methotrexate (MTX), 3) 10/10 MUD bone marrow (BM) with a CNI and MMF or MTX, 4) 9/10 HLA-MUD BM or PBSC (9/10 UD), 5) T cell replete haploidentical donor (haplo) BM or PBSC, and 6) matched sibling donor (MSD) BM or PBSC. Exclusion criteria included in vitro manipulated grafts and CBT recipients who received anti-thymocyte globulin or alemtuzumab. Patients were directly matched for disease and status at transplant and propensity score matching was used for prior allograft, age, KPS, and conditioning regimen. Endpoints included engraftment, GVHD, NRM, relapse, progression-free survival (PFS), overall survival (OS), and GVHD-free relapse-free survival (GRFS). The EBMT attempted to identify 3 controls for each patient. If no control was identified for a UM171 patient, the latter was excluded from the analysis. Results: Between 17 and 21 UM171 CB patients were compared to 36 to 62 controls depending on the donor group as 1-3 controls could not be identified for each patient (Table 1). Median follow-up for the UM171 group was 36 months and generally longer for the controls. Neutrophil engraftment with UM171 CB was similar to all donor groups except slower for CB and MUD BM. Platelet engraftment was consistently slower for UM171 CB except when compared to conventional CB. The incidence of severe acute GVHD was similar across all donor groups. As there was no severe chronic GVHD in the UM171 group, the latter was associated with less extensive/severe chronic GVHD compared to MUD (PBSC and BM) and MSD. There was a trend towards lower NRM for UM171 CB compared to haplo and 9/10 UD but it did not reach statistical significance. PFS, OS and GRFS were all better with UM171 CB compared to haplo. Finally, GRFS was improved with UM171 CB when compared to MUD PBSC (Figue 1), 9/10 UD, and MSD. Conclusions: This registry matched case-control analysis demonstrated real-word evidence suggesting UM171-expanded CBT recipients have improved outcomes compared to other donor types. More specifically and due to the absence of severe chronic GVHD with UM171 CB, GRFS was better with UM171 CB when compared to other graft sources except for CB and MUD BM. Also, OS and PFS were superior with UM171 CB compared to haplo donors. Limitations of this study included the small number of UM171 patients, the inability to identify controls for each case, and certain missing data for the controls. UM171 expansion of CB appeared to achieve the desired outcome of maintaining benefits of CB while removing its disadvantages. Thus, prospective randomized studies are warranted to confirm these results.

Trends in Allogeneic Stem Cell Transplantation for Good Risk Acute Myelogenous Leukemia in First Complete Remission: A Longitudinal Study of > 15 Years from the ALWP/EBMT

Background: Favorable acute myelogenous leukemia (AML) includes AML with t (8:21), inv (16), and those with NPM1 without FLT3- ITD without adverse cytogenetics (ELN 2022). The incidence of relapse (RI) in favorable-risk AML with chemotherapy is 35%-40%. Although RI is ~20% lower with allogeneic transplantation (HSCT), transplantation is usually not indicated in favorable risk AML at first complete remission (CR1) due to transplant-related mortality. However, in recent years, HSCTs have been associated with significantly lower non relapse mortality (NRM) and better outcomes. Methods:Our aim was to assess outcomes of HSCT in favorable risk AML (t (8:21), inv (16), and NPM1 mutFLT3 WT) in CR1, comparing 3 time periods: 2005-2009, 2010-2014, and 2015-2021. Statistical tests included a multivariate analysis (MVA) adjusting for potential confounding factors performed using a Cox proportional-hazards regression model for main outcomes. Results: 1850 patients (pts) were included, 526 with t (8:21), 625 with inv (16), and 699 with NPM1 mutFLT3 WT (normal karyotype). 222 pts were transplanted in 2005-2009, 392 in 2010-2014, and 1236 in 2015-2021. As the follow-up period differed, being 103.1 (IQR, 92.1-114.0), 78.3 (IQR, 69.4-86.3), and 32.0 (IQR, 29.5-34.5) months, respectively (p<0.0001), all survival events were censored at 3 y. Pts undergoing HSCT in 2015-2021 were older, with a median age of 50.9 (range 18.2-76.4) vs40.4 (range 18.3-67.7) and 42.4 (range 18.4-71) y, in those transplanted in 2005-2009 and 2010-2014, respectively (p<0.0001). More pts >50 y of age were transplanted in the latest period with 52.7% vs the 2 earlier periods 27.9% and 32.1% (p<0.0001) and figures for >60 y were 25.4% vs 8.1% and 11% (p<0.0001), respectively. In 2005-2009 the most frequent diagnosis was t (8:21) at 44.6%, while in 2015-2021, it was NPM1 mutFLT3 WT at 45.6% (p<0001). In 2005-2009, the most frequent donors were matched siblings (MSD) (63.1%), while in 2015-2021 they were unrelated (UD) (50.7%). Haploidentical (haplo) transplants increased from 5.9% to 14.5% (p<0.0001). Bone marrow grafts decreased from 24.8% to 13.2%, while peripheral blood (PB) grafts increased from 75.2% to 86.8% (p<0.0001). Conditioning was myeloablative in 69.8%, 64.8%, and 60.2% and was reduced intensity in 30.2%, 35.2%, and 39.8% in pts transplanted in 2005-2009, 2010-2014, and 2015-2021 (p=0.014). Graft-versus-host disease (GVHD) prophylaxis with in vivo T cell depletion or post-transplant cyclophosphamide (PTCy) was more frequent in 2015-2021 compared to the other two periods (p<0.0001). Day 60 engraftment (ANC >0.5 x 10 9/L) was 98.2 % vs 98.4% vs 98.5% (p=0.17). Day 180 incidence of acute (a) GVHD grade II-IV was 18.2%, 21.1%, and 21.6%; grade III-IV was 5.1% 5.7%, and 7.3% while the incidence of 3-y chronic (c) GVHD was 49.3%, 50.4% and 39.2%. On MVA the incidence of total cGVHD was reduced in HSCTs performed >2015 compared to those performed in 2005-2009, hazard ratio (HR) =0.74 (95% CI 0.56-0.99, p=0.046) and GVHD-free, relapse-free survival (GRFS) improved for pts transplanted from 2010-2014 vs those transplanted in 2005-2009, HR=0.74 (95% CI 0.56-0.98, p=0.037) (Figure 1). All other HSCT outcome parameters including NRM, RI, leukemia-free survival (LFS), and overall survival (OS) did not differ (Figure 1) with no improvement >2015 compared to 2010-2014 (Figure-1 A). LFS, OS, and GRFS were superior in pts with t (8:21) with HR=1.32 (95% CI 1.03-1.68, p=0.026), HR=1.38 (95% CI 1.04-1.83, p=0.027) and HR=01.25 (95% CI 1.02-1.53, p=0.035), respectively. Other poor prognostic factors were older pt age (by 10 y) for NRM and OS; 10/10 and 9/10 UD vs MSD for aGVHD II-IV (9/10 also for III-IV aGVHD) and haplo vs MSD for NRM, OS, aGVHD II-IV, and total cGVHD. The combination of female donor to male pt was a poor prognostic factor for NRM, OS, GRFS, and cGVHD. In vivo T cell depletion was a positive prognostic factor for GRFS and reduced incidence of aGVHD and cGVHD. PTCy was associated with a lower incidence of cGVHD and PB grafts with an increased risk of total cGVHD. Conclusions: In this retrospective analysis of HSCT in pts with favorable risk AML in CR1, transplanted over 16 years, we observed an increased number of transplants in pts >60y, from UD and haplo with PB grafts and in vivo T cell depletion or PTCy as GVHD prophylaxis. Most importantly, 3-y GRFS improved >2010 and total cGVHD reduced >2015, while other HSCT outcome parameters have not changed.

Impact of TP53 Allelic State on Outcomes of Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation for Myelodysplastic Neoplasm

Background : Tumor protein p53 ( TP53) mutations are associated with dismal outcomes in myelodysplastic neoplasms (MDS). However, the impact of TP53 allelic state in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for MDS has not been fully explored. Method: We conducted a multi-center study in 347 MDS patients undergoing allo-HSCT between January 2017 and October 2022, with the median follow-up time among survivors of 28.6 (range, 4.7 - 76.6) months, and 45 had TP53 mutations among them. Results: Twenty-one patients were detected with TP53 monoallelic mutations ( TP531mut), while 24 had multiple hits ( TP53multi). Complex karyotype was more common in patients with mutated TP53 (52.4% of patients with TP531mutand 75.0% of patients with TP53multi), whereas this proportion was only 10.6% in patients with wild-type TP53 ( TP53wt). The prognosis varied according to different TP53 state, showing the 2-year overall survival (OS) rates of 51.4% (95% confidence interval [CI]: 33.7% - 78.6%) for TP531mut group versus 15.8% (95% CI: 3.3% - 76.4%) for TP53multi group versus 73.5% (95% CI: 68.5% - 78.9%) for TP53wt group ( P<0.001), and the 2-year cumulative incidence of relapse (CIR) rates of 28.6% (95% CI: 11.2% - 48.8%) for TP531mut group versus 47.3% (95% CI: 18.3% - 71.9%) for TP53multi group versus 10.8% (95% CI: 7.5% - 14.9%) for TP53wt group ( P<0.001). Similarly, the leukemia-free survival (LFS) and graft-versus-host disease-free/relapse-free survival (GRFS) of patients with TP531mut or TP53multi were obviously lower than those with TP53wt (both P<0.001). However, there was no significant difference on non-relapse mortality among these three groups ( P=0.424). The adverse effects of TP53 mutationson OS, LFS, GRFS and CIR were also found in patients undergoing haploidentical HSCT or those with molecular International Prognostic Scoring System high- and very high-risk categories (all P<0.05). In the subgroup with complex karyotype ( n = 32 with non-mutated TP53 and n = 29 with mutated TP53), significantly inferior OS, LFS and GFRS and higher CIR were observed in patients with mutated TP53 while in the subgroup without complex karyotype ( n = 270 with non-mutated TP53 and n = 16 with mutated TP53), there were no differences in these prognostic indicators (all P>0.05). Notably, among patients who received conventional conditioning regime without hypomethylating agents (HMA) ( n = 264 with non-mutated TP53 and n = 38 with mutated TP53), the inferior 2-year OS, LFS and GRFS rates, and the higher 2-year CIR rate of patients still presented in TP53 mutant patients(all P<0.05), but among those receiving conditioning regime containing HMA, similar outcomes were found between mutated ( n = 7) and non-mutated ( n = 38) TP53 groups (all P>0.05). Multivariable cox proportional hazards models demonstrated that monoallelic TP53 state was an independent risk factor for survival and relapse (HR OS=2.859, 95% CI: 1.372 - 5.957, P=0.005; HR LFS=2.566, 95% CI: 1.342 - 4.905, P=0.004; HR GRFS=2.146, 95% CI: 1.106 - 4.163, P=0.024; HR CIR=2.507, 95% CI: 1.033 - 6.086, P=0.042), and multi-hit TP53 state also predicted worse outcomes (HR OS=3.038, 95% CI: 1.453 - 6.356, P=0.003; HR LFS=2.716, 95% CI: 1.383 - 5.336, P=0.004; HR GRFS=1.882, 95% CI: 1.002 - 3.535, P=0.049). C onclusions: Monoallelic and multi-hit TP53 state identify a high-risk group for poor outcomes in MDS patients undergoing allo-HSCT, complex karyotype could amplify the adverse prognostic effect of TP53, and these patients might benefit from receiving conditioning regime containing HMA.

Relapse Incidence Post Unrelated Allogeneic Stem Cell Transplantation with Post-Transplant Cyclophosphamide (PTCy) Versus Conventional Anti-Graft Versus Host Disease Prophylaxis in Patients with Acute Myeloid Leukemia: A Study on Behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Background: Recently, the BMT CTN 1703 phase III study compared post-transplant cyclophosphamide with tacrolimus with mycophenolate mofetil (PTCy/TAC/MMF) to TAC /methotrexate (MTX) as graft- versus-host disease (GVHD) prophylaxis post allogeneic transplantation (HSCT), demonstrating a lower incidence of severe acute (a) GVHD and chronic (c) GVHD and better GVHD-free, relapse-free survival (GRFS). The control arm did not include anti-thymocyte globulin (ATG), used in many centers for GVHD prophylaxis. Methods: The study aim was to compare PTCy with TAC or cyclosporine A (CSA) and MMF (PTCy/TAC or CSA & MMF) to ATG combined with TAC and MTX (ATG/TAC/MTX) in acute myeloid leukemia (AML) patients (pts) undergoing HSCT from matched siblings (MSD) or 9-10/10 unrelated donor (UD) in first complete remission (CR1). Statistical tests included a multivariate analysis (MVA) adjusting for potential confounding factors using a Cox proportional-hazards regression model for main outcomes. Results: 6050 pts met the inclusion criteria, 402 received PTCy/TAC or CSA & MMF and 5648 received ATG/TAC/MTX as GVHD prophylaxis. Median follow-up was 23.4 (IQR, 20.3-24.9) and 41.8 (IQR, 39.6-43.3) months (p<0.0001). The median year of the transplant was 2018 (2010-2020) and 2016 (2007-2020) (p<0.0001). Pts in the PTCy/TAC or CSA & MMF group were younger, with a median age of 48.7 (range 18-5.6) versus 51.5 (8-77.8) years (p=0.024). The diagnosis was de novo AML in 84.1% vs 85.3% and secondary (s) AML in 15.9% vs. 14.7% (p=0.49). The cytogenetic risk was categorized as intermediate (70.9% vs. 67.1%), adverse (22.2% vs. 25.7 %), and favorable (6.9% vs. 7.2%) for pts in the PTCy/TAC or CSA & MMF and ATG/TAC/MTX groups, respectively (p=0.35) (data missing for 2214 pts). Karnofsky performance status (KPS) did not differ between the groups. There was a higher frequency of pt cytomegalovirus (CMV) seropositivity and female (F) donor to male (M) pt combination in the PTCy/TAC or CSA & MMF versus the ATG/TAC/MTX groups, 77.8% vs. 71.8% (p=0.009) and 18.4% vs. 14.4% (p=0.029), respectively. More pts in the PTCy/TAC or CSA & MMF group received reduced intensity conditioning (RIC) 51.5% versus 41.1% in the ATG/TAC/MMT group, respectively (p<0001). Day 60 neutrophil engraftment (ANC >0.5 x 10 9/L) was 98.7% vs. 98.6% (p=0.84). Day 180 incidence of a GVHD grade II-IV and III-IV was 21.2% vs. 20.4% (p=0.92) and 8.1% vs. 6% (p=0.1), in pts receiving PTCy/TAC or CSA & MMF versus the ATG/Tac/MTX GVHD prophylaxis, respectively. The 2-year (y) total and extensive chronic (c) GVHD were 33.7% vs. 30% (p=0.09) and 10.7 % vs. 11.2% (p=0.81), respectively. GVHD was the cause of death in 11.6% vs. 13.9% of pts who died. In the MVA, both aGVHD (grade II-IV or III-IV) and cGVHD (total or extensive) did not differ between the groups with hazard ratios (HRs) =1.15 (95% CI 0.86-1.53, p=0.35), HR=0.87 (95% CI 0.56-1.34, p=0.52), HR=0.91 (95% CI 0.7-1.18, p=0. 47 and HR=1.51 (95% CI 0.96-2.36, p=0.074). Two-y NRM was significantly lower in pts that received PTCy/TAC or CSA & MMF versus ATG/TAC/MTX for GVHD prophylaxis, HR=1.57 (95% CI 1.07-2.3, p=0.022). Other HSCT outcome parameters did not differ between the groups. The HR for 2-y RI was 0.99 (95% CI 0.77-127, p=0. 93). The HRs for 2-y leukemia-free survival (LFS), overall survival (OS), and GRFS were HR=1.15 (95% CI 0.94-1.42, p<0.18), HR=1.18 (95% CI 0.94-1.49, p=0.16) and HR=1.12 (95% CI 0.93-1.36, p=0.22), respectively. Donor type and conditioning regimen were poor prognostic factors for grade II-IV, III-IV aGVHD, and total and extensive cGVHD. For cGVHD, additional poor prognostic factors were F donor to M pt combination and pt CMV seropositivity. Poor prognostic factors for LFS, OS, and GRFS were 9/10 UD, age (by 10 y), sAML, adverse-risk cytogenetics, lower KPS, and pt CMV seropositivity. For NRM, factors were the same apart from cytogenetics risk which was not a prognostic factor. In addition, time from diagnosis to HSCT was a prognostic factor for NRM and RI. Other poor prognostic factors for RI were lower KPS and pt CMV seropositivity. Conclusions: In this registry-based retrospective analysis, comparing PTCy in combination with TAC or CSA and MMF to ATG in combination with TAC and MTX as GVHD prophylaxis, we observed a similar incidence and severity of both aGVHD and cGVHD. NRM was significantly lower with the PTCy-based GVHD prophylaxis, while all other transplant outcome parameters were similar.

Patient-Reported Outcomes of BMT CTN 1703: A Randomized Phase III Study for Gvhd Prophylaxis - a Quality of Life Evaluation

Introduction A randomized phase III trial of post-transplantation cyclophosphamide (PTCy), tacrolimus, (Tac), and mycophenolate mofetil (MMF) versus tacrolimus/methotrexate (Tac/MTX) for graft-versus-host disease (GVHD) prophylaxis showed superior graft-versus-host disease-free, relapse-free survival (GRFS) in the PTCy-containing arm (NEJM, 2023). Here, we report the effect of GVHD prophylaxis on patient-reported outcomes and impact on quality of life (QOL). Methods The QOL study component of BMT CTN 1703 employed four primary endpoints: Lee Chronic GVHD Symptom Score and the PROMIS subscales of physical function, gastrointestinal symptoms, and satisfaction with participation in social roles. Secondary endpoints included hemorrhagic cystitis symptoms and Lee symptom subscale differences, with questionnaires to English and Spanish-speaking participants at enrollment and on Days 100, 180, and 365 post-transplant. Given the risk of missing assessments, an inverse probability weighted-independent estimating equations (IPW-IEE) model was applied for score comparison between arms, adjusting for baseline score, assessment time, age, donor type, disease risk index (DRI), planned conditioning regimen, and planned use of post-transplant maintenance therapy. Significance was declared at a 1.25% level for score comparisons between arms after Bonferroni correction for multiple testing. The analysis approach classified patients according to the intention-to-treat principle. Results QOL survey completion rates for patients at each timepoint were similar, exceeding 70% in each study arm. With the Lee Chronic GVHD Symptom Scale, higher scores indicate more severe symptoms. The IPW-IEE models indicated that the Lee Chronic GVHD Symptom Scale total scores were significantly lower in the PTCy arm compared to Tac/MTX at day 100 (mean difference [MD] -2.22, 99% confidence interval [CI] -5.05 to 0.61) and day 365 (MD -1.84, 99% CI -5.13 to 1.45, p=0.01 for overall treatment effect across all timepoints, Figure 1). Nutrition subscores were significantly better with PTCy at day 100 (MD -2.41, 99% CI -5.06 to 0.24, p=0.0014). Mouth scores were significantly better in the PTCy arm at day 365 (MD -7.09, 99% CI -13.21 to -0.98, p=0.0035). Patients over 65 years of age had better psychological subscores across the study population (MD -4.80, 99% CI -8.91 to -0.69, p=0.0026); no interaction was found between age and study treatment. Patient-reported hemorrhagic cystitis symptoms showed no significant difference between the study arms at any post-transplant time point. There was no significant treatment effect observed on the 3 PROMIS subscales. Across the entire study population, both relapse and acute GVHD were associated with worse scores on the Lee Symptom Scale, and PROMIS physical function, gastrointestinal symptoms, and social functions subscales. Chronic GVHD was associated with worse scores on the Lee Symptom Scale only, not the PROMIS subscales. No associations were found between patient-reported QOL at baseline and 1-year GRFS, disease-free survival, or overall survival. Conclusions The PTCy arm of BMT CTN 1703 showed superior GRFS, and this study confirms better patient-reported outcomes with PTCy. Patients who received PTCy showed better nutrition and mouth subscores on the Lee Chronic GVHD Symptom Scale compared to those who received Tac/MTX, possibly due to lower observed rates of severe acute and chronic GVHD in the PTCy arm. No association was found between patient-reported baseline quality of life and survival endpoints, suggesting the necessity of further research to elucidate the interplay of treatment strategies, patient factors, and their impact on long-term outcomes.

Non-T-Depleted Haploidentical Transplantation with Post-Transplant Cyclophosphamide in Patients with Relapsed/Refractory Secondary Versus De Novo AML: A Study from the ALWP/EBMT

Background: Secondary acute myeloid leukemia (sAML) is a distinct type of AML. Transplantation, a potentially curative therapy, outcomes are inferior compared to de novo AML. We recently demonstrated (J Hematol Oncol 2023) that results of non-T-cell depleted haploidentical stem cell transplantation (HaploSCT) with post-transplant cyclophosphamide (PTCy) in sAML in complete remission are not significantly different from those in denovo AML. However, the challenge in relapse (Rel)/primary refractory (PR) AML is much higher. Methods:The study aim was to compare the outcomes of HaploSCT with PTCy, performed between 2010 and 2022, in first Rel(Rel1)/PR sAML versus those in Rel1/PR de novo AML. Statistical tests included a multivariate analysis (MVA) adjusting for potential confounding factors using a Cox proportional-hazards regression model for main outcomes. Results: A total of 719 patients (pts) met the inclusion criteria, 129 with sAML and 590 with de novo AML. Median follow-up was 45.6 (IQR] 39.1-57.9) and 43.5 (IQR, 37.5-48.0) months for pts with sAML and de novo AML, respectively (p=0.20). Pts with de novo AML were younger, with a median age of 55.4 (range 18-77.8) versus 61.3 (21-78.8) years, (p<0.0001). The median year of the transplant was 2018 (2010-2011) in pts with sAML and 2017 (2010-2022) in those with de novo AML (p=0.62) and 65.1% and 57.6%, were male (p=0.11). In 81.4% of sAML pts, the antecedent hematological disorder was myelodysplastic syndrome. The cytogenetic risk was categorized as intermediate (58.6% vs 59.4%), adverse (37.4% vs 34.7%), and favorable (4% vs 5.9%) for pts with sAML and de novo AML, respectively (p=0.75) (data missing for 145 pts). A higher percentage of pts with sAML vs de novo AML had PR disease (73.6% vs 58.6%) (p=0.002). HCT-CI was higher in the sAML vs the de novo AML group, with HCT-CI >3 in 40.3% vs 21.9%, respectively (p<0.0001), while the Karnofsky performance status (KPS) did not differ. There was no difference in the frequency of cytomegalovirus (CMV) seropositivity and female donor to male pt combination between the two pt groups. Reduced intensity conditioning was received by 60.2% and 52.2% of the sAML and de novo AML pts, respectively (p=0.1), with thiotepa/busulfan/fludarabine being the most frequent regimen for both groups (38.8% vs 42%, respectively). Graft source was mainly peripheral blood stem cells (PB) in both sAML (69.8.5%) and de novo (66.8%) groups. All pts received PTCy as graft- versus-host disease (GVHD) prophylaxis in combination with immunosuppression, which was cyclosporine A (CSA)/ mycophenolate mofetil in 41.1% vs 52.9% and CSA/tacrolimus in 41.1% vs 33.6% respectively. Cumulative incidence of absolute neutrophil count (ANC) >0.5 x 10 9/L at day 60 was 83.5% vs 88.4% (p=0.13), respectively. Day 180 incidence of acute (a) GVHD II-IV and III-IV was 20% vs 26.9% (p=0.12) and 8.9% vs 10.4%, (p=0.21), respectively. The 2-year (y) total and extensive chronic (c) GVHD were 25.3% vs 20.7% (p=0.27) and 12.5 % vs 10.3% (p=0.46), respectively. In MVA HaploSCT outcomes did not differ significantly between the Rel1 /PR sAML and de novo groups; 2-y non-relapse mortality (NRM) hazard ratio (HR)=1.38 (95% CI 0.96-1.98, p=0.083). Infections and GVHD were the cause of death in 20.8% and 9.3% of pts who died. The HR for 2-y relapse incidence (RI) was 0.68 (95% CI 0.4.7.-1.00, p=0.051) and RI was the main cause of death in 40.9% and 59.3% of pts who died, respectively. The 2-y leukemia-free survival (LFS), overall survival (OS), and GVHD-free, relapse-free survival (GRFS) did not differ between the two groups with HR=0.99 (95% CI 0.76-1.28, p<0.94), HR=0.99 (95% CI 0.77-1.29, p=0.973) and HR=0.99 (95% CI 0.77-1.27, p=0.94), respectively. Adverse-risk cytogenetics was a poor prognostic factor for RI and both higher age (per 10y) and lower KPS were poor prognostic factors for NRM. Adverse-risk cytogenetics and lower KPS were poor prognostic factors for LFS, OS, and GRFS. In addition, pt CMV seropositivity was a poor prognostic factor for OS. Finally, PB grafts were associated with increased risk of all grades and severe aGVHD. Conclusions: In this registry-based retrospective analysis, we observed similar outcomes, of HaploSCT with PTCy for Rel1/PR sAML compared to Rel1/PR de novo AML, with HaploSCT being able to rescue about one-third of the pts. However, relapse is still 43%. The recently approved novel agents for sAML will hopefully further improve sAML outcomes.

Prognostic Factors Impacting Post-Transplant Outcomes in Adult T-Cell Acute Lymphoblastic Leukemia: A Registry-Based Study By the EBMT Acute Leukemia Working Party

Background: T-cell acute lymphoblastic leukemia (T-ALL) predominantly affects individuals in late childhood and young adulthood and historically had high mortality rates. The outcome of Pediatric inspired chemo protocols in the T-ALL have improved in the past years due to the advancement in treatment and supportive care but the data is less mature, although adult patients still face challenges. Limited studies have directly explored the impact of patient- and transplant-related factors on post-transplant outcomes in adult T-ALL patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methods: A retrospective registry-based analysis was conducted across multiple centers using data from the European Society for Blood and Marrow Transplantation (EBMT) registry. Inclusion criteria were adult T-ALL patients (>18 years old) who underwent their first allo-HSCT in first complete remission from matched sibling donors (MSD), unrelated donors (UD) (10/10 or 9/10) or haploidentical donors between 2010 and 2021. Cord bloods were excluded. Multivariable Cox regression analysis was performed to examine the associations between patient/transplant characteristics and outcomes. Results: A total of 1907 patients were included in the study. The median age at transplant was 33.4 years (18.1-75). The median follow up was 2.9 years (2.6-3.1), and the median year of HSCT was 2016 (2010-2021). Patients were 70 % male with 67% being CMV-positive, at the time of transplant. Donors were predominantly male (64%), and (23%) of transplants involved female donors to male patients. The median period between diagnosis and HSCT was 5.9 months (0 -23.8). Most transplants were from matched sibling donors (MSD) (45%) followed by UD (43%) and 12% were from Haploidentical transplants. Most patients underwent myeloablative conditioning with total body irradiation (TBI)-based regimens (69%) and most patients received peripheral blood stem cells (84%). Cyclosporine with methotrexate was the most common graft-versus-host-disease (GVHD) prophylaxis (54 %). In vivo T cell depletion was used in 44%. The 2-year overall survival (OS) was 69.4%, and leukemia -free survival (LFS) was 62.1%. The cumulative incidence of acute GVHD (aGVHD) grades II-IV at 100 days was 32.6%, and grades III-IV was 10%. The cumulative incidence of chronic GVHD (cGVHD) at 2 years was 37.3%, and extensive cGVHD was 16.8%. Multivariate analysis yielded significant associations between patient/transplant characteristics and outcomes. Advanced age at transplant was associated with poorer outcomes, including LFS (HR=1.11, p=0.004), GVHD-free, relapse-free survival (GRFS) (HR=1.06, p=0.04), OS (HR=1.12, p=0.002), and higher non-relapse mortality (NRM) (HR=1.23, p=0.001); HR for 10y increment. A later year of HSCT was associated with improved GFRS (HR=0.89, p=0.001), OS (HR=0.9, p=0.02), and decreased NRM (HR=0.82, p=0.008), aGVHD II-IV (HR=0.83, p=0.001), and cGVHD (HR=0.8, p=0.001); HR for 3y increment. TBI was specifically superior with improved LFS (HR=0.79, p=0.02), GRFS (HR=0.83, p=0.04), and lower relapse incidence (RI) (HR=0.65, p=0.001). Female-to-male transplant combination had a negative impact on GFRS (HR=1.21, p=0.02), OS (HR=1.23, p=0.048), and on the risk of cGVHD in general (HR=1.39, p=0.002) and specifically extensive cGVHD (HR=1.47, p=0.01). The use of in vivo T-cell depletion had significant benefits in terms of GFRS, aGVHD grade III-IV, cGVHD, and extensive cGVHD. Conclusion: This large study identified prognostic factors, such as age at transplant, donor type, and conditioning regimen, in influencing key outcomes including OS, LFS, GVHD incidence, and NRM in adult T-ALL patients undergoing allo-HSCT. Importantly, a significant improvement over time in post-transplant outcomes was noted. These findings hold great promise for new adapted treatment strategies and can serve as a benchmark for future studies in that setting.

Checkpoint Inhibitors and Allo-SCT in Hodgkin Lymphoma: A Matter of Time - a Study By the SFGM-TC

Introduction: Allogeneic stem cell transplantation (allo-SCT) for patients with relapsed/refractory Hodgkin lymphoma (r/R HL) after autologous transplantation is now an established option. Many patients receive Check-Point Inhibitors (CPI) as relapse treatment. Nevertheless, concerns have been previously reported on higher risk of acute graft versus host disease (aGVHD) after CPI exposure, without any control group to elucidate risk factors. Methods: We conducted a multicentric retrospective case control study on behalf of the Francophone Society for Bone Marrow Transplantation and Cell Therapy to compare outcomes after allo-SCT for patients with r/R HL who were exposed or not exposed to CPI. Results: Between 2015 and 2018, 149 patients underwent allo-SCT for r/R HL in 21 centers. CPI was used for 50 patients (n=48 Nivolumab, n=2 Pembrolizumab). We did not identify any differences regarding baseline characteristics. Reduced intensity conditioning (RIC) was commonly used (90.2%), with Peripheral Blood Stem Cells (75.7%). A majority of patients had haploidentical (44.6%), followed by siblings (28.4%), matched unrelated (24.3%) and mismatched unrelated donors (2.7%). Cumulative incidence (CI) of aGVHD grade ≥II in the whole cohort was 39.6% and 14.8% developed a severe form (grade III-IV). There were no differences between CPI (n=50) and no CPI cohorts (n=99), regarding CI of aGVHD of any grade (respectively 58% and 57.6%, p=1.00), grade ≥II (respectively 36% and 41.4%, p=0.65), severe aGVHD (grade III-IV, respectively 12% and 16.2%, p=0.67) and chronic GVHD (respectively 26% and 34.3%, p=0.24), as described in Table 1. We did not observe excess of mortality from GVHD between both groups. The time interval between the last CPI injection and allo-SCT was found to be the only significant factor associated with a higher incidence and severity of aGVHD, as depicted in Figure 1. The median time from the last CPI injection and allo-SCT was 50 days [33;103]. Specifically, within 30 days, the incidence of severe aGVHD was significantly increased at 41.7% compared to only 2.7% in the control group (p=0.002). No severe forms were observed after 60 days, but it persisted a higher risk of aGVHD grade ≥II even after 60 days of delay. Thus, a higher percentage of patients required systemic therapy for aGVHD within 120 days compared to after 120 days (45% vs 0% respectively, p=0.03). The delay of CPI treatment did not impact the CI and severity of chronic GVHD or CI of relapse after allo-SCT. Of note, post-transplant cyclophosphamide did not reduce CI of aGVHD. With a median follow-up of 34.7 months, the 2-year Overall Survival, Relapse Free Survival and GVHD free, Relapse Free Survival (GRFS) were respectively 69.9% (IC95 41.1-78.5), 67.1% (IC95 58.8-76.7) and 48.5% (IC95 40.3-58.4), without differences between CPI and no CPI cohorts. Two-year non relapse mortality was 17.4% in whole cohort, without hepatic sinusoidal obstruction syndrome nor steroid-requiring febrile syndrome in CPI cohort. Conclusion: CPI use before allo-SCT within 60 days before allo-SCT can lead to significant severe aGVHD, with persisting higher risk of aGVHD grade ≥II even after 60 days of delay. This highlights the importance of exercising caution when administering CPI injections within 60 days before allo-SCT. There is need to develop GVHD prophylaxis strategies in this population at risk. The findings from this study may help inform clinical decision-making and management of HL patients undergoing allo-SCT.

Haploidentical Transplantation with Post-Transplant Cyclophosphamide Versus Single Cord Blood Transplantation for Adults with Relapsed/Refractory Malignant Lymphoma

Introduction Although the treatment of malignant lymphoma has diversified with the advent of chimeric antigen receptor T-cell therapy and other novel agents, allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a curative treatment for some patients with relapsed/refractory malignant lymphoma (R/R ML). R/R ML eligible for allo-HSCT often requires urgent transplantation, making human leukocyte antigen (HLA)-haploidentical transplantation with post-transplant cyclophosphamide (PTCY-haplo) or cord blood transplantation (CBT) a promising option when HLA-matched donors are unavailable. PTCY-haplo has recently been reported to achieve similar or better clinical outcomes than CBT for other hematological malignancies, though data regarding R/R ML are insufficient. Therefore, this study compares PTCY-haplo and CBT for patients with R/R ML using the Transplant Registry Unified Management Program 2 (TRUMP2) in Japan. Methods This study included adult patients with R/R ML registered with TRUMP2 who underwent PTCY-haplo and CBT for their first allo-HSCT between January 2013 and December 2021. In this study, R/R ML included mature B-, T-, and NK-cell neoplasms, as defined in the World Health Organization's 2017 classification. Patients undergoing allo-HSCT for Hodgkin's lymphoma, aggressive NK-cell leukemia, chronic active Epstein-Barr virus (EBV) infection, systemic EBV-positive T-cell lymphoma of childhood, or adult T-cell leukemia/lymphoma were excluded. The primary endpoint was 3-year overall survival (OS). A Cox proportional hazard regression model for OS was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) in the multivariate analysis. The following factors were included in the multivariate model: donor type, age, sex, performance status, Hematopoietic Cell Transplantation-specific Comorbidity Index score, disease status at allo-HSCT, conditioning regimen, cytomegalovirus seropositivity, and disease linage. The secondary endpoints were 3-year progression-free survival (PFS), 3-year graft versus host disease (GVHD)/relapse-free survival (GRFS), 3-year cumulative incidence of relapse and non-relapse mortality (NRM), 28-day cumulative incidence of neutrophil engraftment, 100-day cumulative incidence of platelet engraftment, 100-day cumulative incidence of grade II-IV and grade III-IV acute GVHD, and 3-year cumulative incidence of any and extensive chronic GVHD. Results A total of 1093 patients, including 223 who underwent PTCY-haplo and 870 who underwent CBT, were included in the study. The median age was 54 years (interquartile range, 44-61 years), and 616 (56%) patients had B-cell lymphoma. The PTCY-haplo group included older patients, more patients who were positive for cytomegalovirus antibodies in recipients or donors, and more patients who received a reduced-intensity conditioning regimen. The 3-year OS was 49% (95% CI: 41-56%) in the PTCY-haplo group and 42% (95% CI: 38-45%) in the CBT group (P=0.090). The adjusted HR was 0.88 (95% CI: 0.70-1.09, P=0.20). The PTCY-haplo group had comparable 3-year PFS, 3-year GRFS, 3-year relapse rates, and 3-year NRM as the CBT group. The PTCY-haplo group had higher neutrophil engraftment at 28 days (92.8% [95%CI: 88.5-95.6%] vs 81.6% [95%CI: 78.9-84.0%], P<0.001) and platelet engraftment at 100 days (77.6% [95%CI: 71.5-82.5%] vs 71.0% [95%CI: 67.9-73.9%], P<0.001); similar grade II-IV acute GVHD at 100 days and 3-year cumulative incidences of chronic GVHD and extensive chronic GVHD; and lower grade III-IV acute GVHD at 100 days (7.17% [95%CI: 4.27-11.1%] vs 13.6% [95%CI 11.5-16.0], P=0.01). Conclusion In this population, PTCY-haplo and CBT result in similar 3-year OS after allo-HSCT. Faster engraftment and less severe acute GVHD were noted in the PTCY-haplo group.

Allogeneic Stem Cell Transplantation in Adolescent and Adult Patients with Acute T Cell Lymphoblastic Leukemia / Lymphoma : Single Center Experience of 143 Patients

Background: T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/-LL) is an aggressive hematological neoplasm originates from T-cell progenitors. T-ALL and T-LL are distinguished by the presence of more or <20% marrow blasts, respectively. Allogeneic hematopoietic cell transplantation (SCT) is typically recommended for adults with T-ALL in second or later complete remission (CR2+), but also may be offered to patients in first CR (CR1) with high-risk features. Our center reported previously outcomes of allogeneic HCT (allo-SCT) in 53 adolescent and young adults of T-ALL ( Biol Blood Marrow Transplant. 2012;18(12):1897-1904). Patients and Methods: We analyzed the outcomes of adults (age >14years) with T-ALL who received allo-SCT at King Faisal Specialist Hospital and Research Center between January 1985 and September 2018. Patients eligible for allo-SCT included HR patients in CR1 and any patient in > CR2 or relapse. Patients in CR1 had one or more of the following HR features: WBC count at presentation > 100,000/mm3, residual disease in bone marrow (BM) at day 14 postinduction, central nervous system (CNS) involvement at diagnosis and the need for more than one induction regimen to achieve CR1. Full-intensity conditioning regimens were used for all patients. The majority of patients (95.1%) received cyclophosphamide 60 mg/kg once daily i.v. for 2 consecutive days (total dose, 120 mg/kg), followed by 12 Gy of fractionated total body irradiation (TBI) given in 6 fractions. Seven patients (4.9%) received busulfan 16 mg/kg (1 mg/kg per dose orally every 6 hours over 4 consecutive days) and cyclophosphamide 60 mg/kg once daily i.v. for 2 consecutive days (total dose, 120 mg/kg).Short-course methotrexate plus cyclosporine (MTX/CSA) was the GVHD prophylaxis regimen used, in all patients. Results: 143 patients underwent allo-SCT and were included in this study; some of them were referred in CR for allo- SCT after undergoing induction chemotherapy outside our institution. Median age was 20 years (range, 14-52).Majority of patients were males 116 (80.6%). Extramedullary presentation was reported in 34 patients (23.8 %) with CNS involvement in 15 patients (10.5%). For SCT outcomes, the incidence rates for relapse 27.1%, acute GVHD 45.8%, grade II-IV acute GVHD was 29.9% and that of chronic GVHD was 38.9%, extensive chronic GVHD was 21.5%. GVHD relapse free survival (GRFS) was reported in 27.1%. The majority of relapses occurred within 1 year after SCT. The cumulative incidence of relapse (CIR) at 1 year was 22.4% 95% CI (15.9 - 29.5), at 2 years was 23.8.8% 95% CI (17.2 - 31) and at 5 years was 25.9% 95% CI (19 - 33.3). Other outcomes, Hemorrhagic cystitis (HC) was noted in 9.7%, sinusoidal obstruction syndrome (SOS) 9% The mean time for overall survival (OS) was 166.77 months (95% CI = 136.54 - 197), and the median survival time was 41 months (95% CI = 15 - 266). For the CR1 group was 205.63 months (95% CI = 166.59 - 244.66). At 10 years, OS of the CR1 group was 74.44 months (95% CI = 63.67 - 85.22), and for the > CR2 group was 35.36 months (95% CI = 24.39 - 46.32); p= 0.0001 PFS analysis showed, the overall mean survival time for disease progression at 5 years was 33.16 months (95% CI = 28.77 - 37.54), and the median survival time was 32 months (95% CI = 12 - 55). For the CR1 group was 39.82 months (95% CI = 34.54 - 45.09), and for the >CR2 group was 22.83 months (95% CI = 16.02 - 29.64), p < 0.0001. At 10 years, PFS for the CR1 group was 74.95 months (95% CI = 63.58 - 86.31), and for the >CR2 group was 41.24 months (95% CI = 27.37 - 55.11) with statistically significantly difference, p < 0.0001. On multivariate analysis, chronic GVHD was significantly associated with a lower OS (P=0.006) and PFS (P=0.01).Disease status at SCT remained significantly associated with PFS (P=0.02),but not OS (P=0.07). The presence of extramedullary disease and CNS involvement at diagnosis had no effect on the different outcomes. Conclusions: Allo-SCT could provide better disease control for HR patients with T-ALL/LL in CR1. Dismal outcomes are reported in patients beyond CR1 with early relapses post allo-SCT are almost inevitable. Better understanding of disease's molecular background in addition to MRD applications, could help to identify more patients in CR1 status who might benefit from allo-SCT. Post SCT strategies including maintenance or pre-emptive interventions might be needed to improve SCT outcomes for T-ALL

Graft-Versus-Host Disease after Anti-CD19 Chimeric Antigen Receptor T-Cell Infusion Post Allogeneic Hematopoietic Cell Transplantation: A Transplant Complications and Paediatric Disease Working Parties EBMT Joint Study

Background Anti-CD19 chimeric antigen receptor T-cells (CART) have been incorporated into the therapeutic landscape of B-acute lymphoblastic leukemia (B-ALL) and B-non-Hodgkin's lymphoma (B-NHL). The manufacturing process of commercially available autologous CART in patients relapsing after allogeneic hematopoietic cell transplant (allo-HCT) might include T-cells of donor origin. In this setting, there is limited data on graft-versus-host disease (GvHD) as an off-target effect in patients treated with CART after allo-HCT. We hereby report on a large, retrospective, EBMT registry-based study on GvHD in patients treated with CART therapy after allo-HCT. Methods Inclusion criteria were B-ALL and B-NHL adult and pediatric allo-HCT patients, treated with a first anti-CD19 CART (axicabtagene ciloleucel [axi-cel] and tisagenlecleucel [tisa-cel]) from 2018 to August 2022. The primary study endpoints were the cumulative incidences (CI) of new acute GvHD (aGvHD) and chronic GvHD (cGvHD). Secondary endpoints were the 1-year GvHD relapse-free survival (GRFS), non-relapse mortality (NRM), and overall survival (OS). Overall data was analyzed in a descriptive manner. Results A total of 257 allo-HCT patients treated with anti-CD19 CART were included. One hundred seventy-two patients (66.9%) were ≥18 years old. Tisa-cel was the therapy of choice in 184 patients (71.6%), whereas axi-cel was used in 73 patients (28.4%). More than half of the cohort (57.6%) underwent allo-HCT from unrelated donors. Notably, 109 patients (46.6%) and 38 patients (15%) had previously develop aGvHD and cGvHD between allo-HCT and CART infusion. Table 1 describes data on baseline patient, allo-HCT and CART characteristics of the whole cohort and of patients developing aGvHD and cGvHD. In total, 3 patients developed new aGvHD and 6 patients developed new cGvHD after CART therapy. The 100-day CI of new aGvHD was 1.6% (95% CI, 0.4-4.2) and the 12-month CI of new cGvHD was 2.8% (95% CI, 1.1-5.7). No GvHD was observed in the pediatric cohort. The median time from allo-HCT to CART infusion was 15.8 months (range, 3.8-220.3) and the median times from CART to the development of aGvHD and cGvHD were respectively 44 days (range, 8-81) and 144 days (range, 5-182). The 1-year GRFS and NRM were 52.1% (95% CI 45.6-59.4) and 4.7% (95% CI 2.5-8.1) respectively (Figure 1). With a median follow up of 18.8 months (95% CI, 16.2-23.7), the 1-year OS was 76.8% (95% CI 71.5-82.4). The most frequent cause of death was disease-related in 56 patients (74.6%). Conclusion Together, in this large cohort including adult and pediatric allo-HCT patients treated with tisa-cel and axi-cel after allo-HCT, these data show that the incidence of both aGvHD and cGvHD is very low. Of note, GvHD was not observed in the pediatric cohort. Furthermore, no excessive NRM was observed compared to previously published methods of treating relapse post allo-HCT, being disease progression a major hurdle to optimal outcomes in this cohort of patients.

A Prospective Randomized Clinical Trial Comparing a Calcineurin-Free Gvhd Prophylaxis Regimen with Post-Transplant Cyclophosphamide and Abatacept to Methotrexate and Tacrolimus

Background: Chronic Graft Versus Host Disease (GVHD) is one of the major causes of mortality and morbidity after an allogeneic stem cell transplantation. We hypothesized that we could induce post-transplant tolerance by using the combination of post-transplant cyclophosphamide (PTCy) and abatacept (CTLA4Ig) for GVHD prophylaxis. PTCy can eliminate most host-reactive donor T cells. Abatacept (CTLA4Ig) blocks the costimulatory signals given to naïve T cells during immune reconstitution, thus favoring an anergic phenotype and promoting tolerance towards recipient derived antigens. CTLA4Ig gives an activating signal to NK cells and has therefore the ability to preserve the graft-versus-tumor effect. Methods: We conducted a prospective randomized clinical trial. Patients with hematologic malignancies in need of an allogeneic transplant and with an 8/8 matched related or unrelated donor were randomized 1:1 to tacrolimus and methotrexate for GVHD prophylaxis (SOC arm) or PTCy on days +3 and +4 followed by abatacept on an extended schedule: days +5, +14,+28, +56, +84, +112, +140 and +168 (Aba arm). Patients were stratified by conditioning regimen (myeloablative vs reduced intensity) and donor type (matched sibling vs matched unrelated donor). They received peripherally collected stem cells. The primary endpoint was moderate and severe chronic GVHD at 1 year and the secondary endpoints overall chronic GVHD, Grade II-IV and III-IV acute GVHD rate, overall (OS), disease-free (DFS), and GVHD-relapse-free-survival (GRFS) at on year, transplant related mortality and infection rate. The study stopped enrolling on the SOC arm when abatacept was approved for GVHD prophylaxis and the institutional SOC changed to include abatacept. Results: 40 patients were treated on this study, 25 of which on the aba arm. There were two cases of secondary graft failure (one on each arm) that were excluded from further analysis other than OS. The trial met its primary end point: Kaplan-Meier estimates of moderate/severe cGVHD were 0% on the aba and 65.8% on the SOC arm (p < 0.0001). GRFS was 58.3% in the aba and 21.4% in the SOC arm (p=0.043). There were no treatment related deaths on the aba and two on the SOC arm. There was no statistically significant difference in the rates of OS (92% aba, 80% SOC, p=0.28), DFS (62.5% aba, 85.7% SOC, p=0.103) and infection. Grade III-IV acute GVHD rate was 4.1% on the aba and 20% on the SOC arm (p=0.132), whereas Grade II-IV 12.5% on aba and 35.7% on SOC (p=0.117). There were no cases of acute GVHD of the gut or liver on the aba arm. Overall chronic GVHD rate (including mild) was 9.1% on the aba and 74% on the SOC arm (p<0.0001). Conclusions: The calcineurin inhibitor-free combination of PTCy and abatacept for GVHD prophylaxis is feasible, well tolerated and associated with a very low rate of chronic GVHD and a favorable GRFS rate.

Sitagliptin for Prevention of aGVHD in Patients Received Alternative Donor Transplantations: A Prospective, Multicenter, Open-Label, Randomized Controlled Trial

Background： Acute graft versus host disease (aGVHD) remains one of the most frequent complications following allogeneic hematopoietic stem cell transplantation (allo-HSCT) with high mortality. Traditionally, alternative donor transplantation (ADT) from an unrelated donor or a haploidentical family donor has been reported in an increased incidence of aGVHD and severe GvHD. Sitagliptin is a selective inhibitor of dipeptidyl peptidase 4 (DPP-4; also known as CD26), a transmembrane receptor expressed on T cells which has a costimulatory function in activating T cells. This trial aims to evaluate the safety and efficacy of sitagliptin plus a calcineurin inhibitor, methotrexate (MTX), mycophenolate mofetil (MMF) and antithymocyte globulin (ATG) in the prevention of aGVHD for ADT. Methods： We are performing a prospective, multicenter, open-label, randomized controlled trial (NCT05149365). From 5 HSCT centers in China competitively, patients(pts) who underwent their first allo-HSCT in first or second complete remission (CR) state with hematologic malignancies were received busulfan and cyclophosphamide (Bu/Cy) myeloablative conditioning regimen followed by ADT. 190 eligible pts(18-60 years) were planned randomly assigned in a 1:1 ratio to either a sitagliptin group (600mg sitagliptin taken orally every 12 hours on day -1 to +14, plus conventional prophylaxis including Cyclosporin A(CsA)/ tacrolimus (FK506), MTX, MMF and ATG) and a conventional prophylaxis control group (CsA/FK506, MTX, MMF and ATG). The randomization was based on a computer-generated priori list of 190 binary numbers, with block-balanced with random variable block sizes of two or four pts, without stratification. The primary endpoint was grade II to IV aGvHD by day +100. Key secondary endpoints included severe (grade III or IV) aGvHD by day +100, transplant-related mortality (TRM), relapse-free survival (RFS) and GVHD-free, relapse-free survival (GRFS) from HSCT. At present we have completed pts enrollment and are at the stage of follow-up the study endpoints. Results : From December 2021 to May 2023, a total of 191 pts were enrolled. The ratio of male to female was 113 to 78 with a median age of 38 years (range, 18-60 years). Pts were randomly assigned to the sitagliptin group of 95 and the control group of 96. The clinical and transplantation characteristics at baseline of the intention to treat (ITT) population of the two groups were well balanced (Table1). The last follow-up was on May 30, 2023 and the median follow-up time was 164 (20-512) days. Comparison of the sitagliptin group and the control group by day +100, the cumulative incidence rate of grade II-IV aGVHD was 15.1% and 28.6%, respectively ( P=0.019), and the cumulative incidence rate of grade III or IV aGVHD was 7.6% and 15.9% ( P=0.068); median days of neutrophil engraftment were +11.48 and +11.65 days, respectively (P=0.545); TRM was 3.7% and 7.1% (P=0.454), RFS was 98.7% and 95.9% (P=0.889), respectively and OS of the two groups(96.7% vs 93.6%, P=0.341) was also the same as the RFS. There was no significant difference between the sitagliptin and control groups with regard to cytomegalovirus reactivation, Epstein-Barr virus reactivation, and transplant-related complications (Table 1, Figure 1). The regimen was well tolerated. Only 5(/95) pts discontinued sitagliptin treatment due to adverse events: 4 patients experienced abdominal pain (CTCAE Grade1-2) undergoing sitagliptin therapy 3-7 days and one of them also exhibited hypoglycemia (CTCAE Grade1), which were deemed by clinicians as probable (WHO-UMC) associated with sitagliptin. Symptoms resolved spontaneously within 2 days of cessation. Another patient discontinued treatment due to mild hematemesis initiating sitagliptin therapy only 2 days, which was determined by the clinician as unlikely (WHO-UMC) associated with sitagliptin. Conclusions : Our trial showed sitagliptin combined with conventional prophylaxis (CsA+MTX+MMF+ATG) resulted in a significant reduction of grade II-IV aGVHD in ADT. Furthermore, sitagliptin is ready available, easy of administration, safe, and relatively inexpensive. It remains to be followed up whether it would increase infection and relapse or improve the prognosis of patients after allo-HSCT.

Favorable Outcomes with Low Dose Anti Thymocyte Globulin Based Graft Versus Host Disease Prophylaxis after Mismatched Unrelated Donor Allogenic Hematopoietic Cell Transplantation

DISCUSSION INTRODUCTION Anti thymocyte globulin (ATG) based Graft versus Host disease (GVHD) prophylaxis is widely used for unrelated donor allogeneic hematopoietic cell transplantation (HCT) although the optimal dose remains unclear. Recently, registry based and single centre retrospective analyses have suggested superior outcomes with the PTCy based GVHD prophylaxis regimens when compared to ATG based regimens in mismatched unrelated donor (MMUD) allogeneic HCT, however, these studies all used doses of ATG ≥ 5mg/kg. Outcomes following MMUD allogeneic HCT with lower dose ATG based GVHD prophylaxis regimens have not been extensively studied. Thus, we analysed outcomes of HLA 9/10 MMUD allogeneic HCTs using two low dose ATG based regimens as GVHD prophylaxis at our centre. All adult patients undergoing standard of care allogenic hematopoietic cell transplant at The Ottawa Hospital from January 1 st 2015- December 31, 2022 were included. Data regarding demographics, HLA mismatched allele, conditioning regimen, dose of ATG, time to engraftment, and rates of acute and chronic GVHD was collected. The primary outcome evaluated was overall survival (OS) and secondary outcomes were GVHD-free relapse-free survival (GRFS), cumulative incidence of relapse (CIR) and non-relapse mortality (NRM). Survival outcomes were analyzed using Kaplan Meier analysis. Predictors of survival were identified using Cox-proportional hazards regression model. 77 patients (Males 62.3% (n=48); Median age - 50 years) underwent allogeneic HCT from MMUD. Most common indication for transplant was MDS/AML in 66.2% (n=51) followed by ALL in 11.3% (n=9) patients. Most frequently mismatched locus was HLA A in 37.7% (n= 29) followed by HLA B in 14.3% (n=11). Myeloablative conditioning regimen was received by 76.6% (n=59) while reduced intensity regimens were used in 23.4% (n=18) patients. Rabbit ATG was part of the GVHD prophylaxis regimen in all patients with majority (81%; n=63) receiving 2.5mg/kg and remaining 18.2% (n=14) receiving 4.5mg/kg of the drug. Grade II-IV acute GVHD occurred in 24.7% (n=19) while chronic GVHD occurred in 32.5% (n= 25) patients. After a median follow up of 21 months, relapse occurred in 28.6% (n=22) patients. Two year OS (Fig 1), and GRFS of the whole cohort were 60.6% and 45.3% respectively. 2-year incidence of non-relapse mortality (NRM) and cumulative incidence of relapse (CIR) were 16.9% and 18.2% respectively. Dose of ATG (2.5 mg/kg vs 4.5 mg/kg) was not a predictor of outcomes in either univariate and multivariate analyses. Age more than 50 years, primary diagnosis of lymphoma, reduced intensity conditioning and mismatch in loci other than HLA C were significant predictors of poor OS after univariate analysis. Only primary diagnosis of lymphoma (Hazard Ratio (HR) - 7.76; p=0.045) and mismatch in loci other than HLA C (HR - 9.53; p=0.03) were significant predictors of poor OS after multivariate analysis. When compared to published single centre and registry-based studies using ATG doses ≥ 5 mg/kg, GVHD prophylaxis using ATG doses ≤4.5 mg/kg seems to provide improved outcomes in patients undergoing allogeneic HCT from mismatched unrelated donors (Table 1). Our findings suggest that further studies are needed directly comparing lower dose ATG based regimens to PTCy based regimens to determine the ideal GVHD prophylaxis regimen for patients undergoing allogeneic HCT from HLA mismatched unrelated donors.

Phase II Trial of Reduced-Intensity Fludarabine, Melphalan, and Total Body Irradiation Conditioning Results in Favorable Outcomes with Haploidentical Donor Peripheral Blood Stem Cell Transplant

Introduction High risk hematologic malignancies are curable with allogeneic hematopoietic cell transplant (HCT). Haploidentical (haplo) HCT with post-transplant cyclophosphamide (PTCy) has improved access to transplant in patients lacking an HLA matched donor. However, traditional reduced-intensity conditioning (RIC) with fludarabine/cyclophosphamide/total body irradiation (TBI) for haplo HCT with PTCy is marred by high rates of relapse. This study seeks to optimize the RIC haplo HCT with PTCy platform in older adults with a slight intensification in conditioning and the use of peripheral blood stem cell (PBSCT) grafts in lieu of bone marrow grafts (BMT). Additionally, tacrolimus was substituted by sirolimus based on prior phase II data suggesting favorable rates of graft-versus-host disease (GVHD) after haplo PBSCT with PTCy (Bejanyan, Blood Adv. 2021). We hypothesized that this approach could successfully reduce the risk of relapse and improve disease-free survival (DFS) without substantially increasing non-relapse mortality (NRM). Methods: This single arm, single center phase II trial of haplo PBSCT used a RIC regimen consisting of Melphalan 70 mg/m 2 IV on day -6, fludarabine 30mg/m 2 IV daily on days -6 to -2, and TBI 200 cGy on day -1 (NCT04191187). Subjects received haplo PBSCT with a target dose of 5 x 10 6 CD34+ cells/kg and capped at 7 x 10 6 CD34+ cells/kg. GVHD prophylaxis consisted of PTCy 50 mg/kg on days +3 and +4, mycophenolate mofetfil (MMF) 1 gram three times daily from days +5 to +35, and sirolimus initiated at a target trough of 8-14 ng/mL on day +5 and tapered off between days +100 and +180. Eligibility criteria required a hematologic malignancy as the indication for allogeneic HCT and either age >55 years or a hematopoietic cell transplant comorbidity index (HCT-CI) > 3. The primary endpoint of this study is DFS with a hypothesis that the experimental regimen would have an 18 month DFS of 60% compared to a historic DFS of 40% and 90% power to reject the null hypothesis. Results: A total of 34 subjects were treated on the trial. The median age was 66 years (range: 31-74 years). The HCT-CI score was > 3 in 41%. Acute myeloid leukemia (AML, 44%) was the predominant indication for transplant followed by myelodysplastic syndromes (MDS, 29%). Nine patients (26%) were from underrepresented racial/ethnic minorities (those other than non-Hispanic white). Five patients (15%) received tacrolimus for GVHD prophylaxis before a protocol amendment changed the regimen to sirolimus for the remaining 29 patients (85%). The median follow-up time for 25 surviving patients was 28.5 months . The trial met the primary endpoint with 18-month DFS of 70.5% (90% CI > 59.1%, p=0.002). We observed no primary graft failure events. Neutrophil engraftment by day 30 was achieved in 30 patients (88%), and platelet engraftment by day 60 was achieved in 28 patients (82%). The cumulative incidence of grade II-IV acute GVHD at day 100 was 11.8% (95% CI: 3.6-25.1%). The cumulative incidence of moderate to severe chronic GVHD at 18 months was 9.1% (95% CI: 2.2-22.0%). At 18 months, the cumulative incidence of NRM was 17.7% (95% CI: 7.0-32.2%) and of relapse was 11.9% (3.7-25.4%). GVHD-free relapse-free survival at 18 months was 61.4% (95% CI: 42.9-75.5%) and the overall survival at 18 months was 73.3% (95% CI: 54.9-85.1%). Conclusion: In this completed phase II trial of fludarabine, melphalan 70 mg/m 2, TBI with haplo PBSCT and PTCy/sirolimus/MMF, the primary endpoint was met with an 18-month DFS that was superior to historical control. This was attributable to low rates of relapse without excessive NRM. Acute and chronic GVHD rates were favorable. Pharmacogenomic and pharmacokinetic correlative data is pending and will be included in the final presentation. These promising results merit further investigation to potentially establish this platform as a new standard approach to RIC haplo PBSCT.

Sensitive Molecular Detection of JAK2 V617F Is a Predictive Marker of Relapse in Patients with Myelofibrosis after Allogeneic Stem Cell Transplantation

Background: Myelofibrosis (MF) is a BCR-ABL1-negative myeloproliferative neoplasm (MPN) associated with JAK2 V617F mutation in approximately 50% of patients. Allogeneic stem cell transplantation (alloSCT) is the only curative treatment option for MF but a significant proportion of patients undergoing alloSCT experience relapse. Although measurable residual disease (MRD) is an established predictor of relapse in other hematological malignancies, the dynamics of JAK2 V617F variant allele frequency (VAF) in MF post-alloSCT and its prognostic impact are yet to be clearly delineated. In this study, we assessed the utility of sensitive molecular detection of JAK2 V617F as a marker of post-alloSCT outcomes in MF particularly with respect to the optimal threshold and time points for predicting early relapse. Methods: A retrospective analysis was conducted of consecutive patients with JAK2 V617F-mutated MF receiving alloSCT at our institution between 2016 and 2022. Data on clinicopathological features, alloSCT characteristics, treatment response assessments, graft-versus-host disease (GVHD) and outcomes were collected. JAK2 V617F was enumerated by droplet digital polymerase chain reaction (ddPCR) using the Bio-Rad QX200 ddPCR platform on archived bone marrow or peripheral blood samples at defined time points pre- and post-alloSCT. JAK2 V617F VAF was defined as the percentage of JAK2 V617F mutant copies amongst total JAK2 (mutant plus wild-type) copies, with a routine assay sensitivity of 0.05%. Results: 31 patients with JAK2 V617F-mutated MF underwent alloSCT during the study period (Table 1). Five patients experienced relapse at a median of 14.2 (range: 3.2-22) months post-alloSCT. 13 patients died of infection (n = 5), overt relapse (n = 4) or GVHD (n = 4). After a median duration of follow-up of 17.5 (range: 0.9-77.9) months, the 5-year overall survival (OS) and relapse-free survival (RFS) were 52.8% and 49.6%, respectively. The 2-year cumulative incidences of relapse (CIR) and non-relapse mortality (NRM) were 26.6% and 35.5%, respectively. On univariate analysis, superior OS and RFS were only significantly associated with chronic GVHD ( P = 0.017 and 0.013, respectively). A total of 174 samples were obtained within 1 month of alloSCT (n = 31) and on days +30 (n = 31), +60 (n = 30), +100 (n = 29), +180 (n = 23) and +360 (n = 21) after alloSCT. All patients had detectable JAK2 at the time of alloSCT with a median VAF of 43.8% (range: 0.2-95%). The incidence of JAK2 V617F detection was 45.2% on day +30, 43.3% on day +60, 44.8% on day +100, 34.8% on day +180 and 23.8% on day +360 post-alloSCT. Of 6 patients who received ruxolitinib for GVHD treatment post-alloSCT, one eventually relapsed while the other 5 had undetectable JAK2 prior to ruxolitinib commencement. JAK2 VAF was higher in patients who eventually relapsed than in non-relapsed patients on days +60, +100, +180 and +360 ( P = 0.008, 0.016, 0.001 and <0.001, respectively) (Figure 1). However, JAK2 positivity at each of these time points was not significantly associated with survival outcomes (OS, RFS, NRM or GVHD-free relapse-free survival [GRFS]). Receiver operating characteristic (ROC) analysis indicated that JAK2 VAF on days +100, +180 and +360 post-alloSCT were significant predictors of eventual relapse ( P = 0.022, 0.019 and 0.01, respectively). The optimal JAK2 VAF thresholds at each of these time points were 0.2% (sensitivity 80%; specificity 83.3%; area under curve [AUC] 0.788) at day +100, 7.1% (sensitivity 75%; specificity 94.7%; AUC 0.842) at day +180, and 11.7% (sensitivity 75%; specificity 94.1%; AUC 0.86) at day +360. Comparisons of JAK2 VAF at each time point to the immediately preceding VAF showed that ≥2-fold increases at days +100 (from day +60) and +180 (from day +100) were significantly associated with relapse ( P = 0.002 and 0.001 respectively). Conclusion: Although persistence of JAK2 is common for more than a year post-alloSCT for JAK2 V617F-mutated MF, serial sensitive molecular monitoring of JAK2 at defined time points appears to be a predictive marker of relapse. In this study, doubling of JAK2 VAF at days +100 and +180 post-alloSCT were associated with relapse. These data support the notion that sensitive molecular detection of JAK2 may have a role akin to MRD in informing the pre-emptive use of immunotherapeutic intervention in this setting, including immunosuppression withdrawal and/or donor lymphocyte infusions.

Allogeneic Hematopoietic Stem Cell Transplantation for Elderly Acute Lymphoblastic Leukemia Patients: A Registry Study from the Société Francophone De Greffe De Moelle Et Thérapie Cellulaire (SFGM-TC)

Background There are very scarce data regarding the outcome of elderly patients with acute lymphoblastic leukemia (ALL) who received allogeneic hematopoietic stem cell transplantation (alloHSCT) as consolidation therapy in 1rst or higher complete remission (CR). Most studies evaluating the benefit of alloHSCT in ALL include both young and elderly populations. Thus, the optimal conditioning regimen still need to be determined in a frail population represented by patients over 60 years old. In addition, total body irradiation (TBI) dose is of first importance, as prior reports demonstrated its potential higher anti-leukemic effect. We here present the outcome of ALL patients older than 59 years from the Société Francophone de Greffe de Moelle et Thérapie Cellulaire (SFGM-TC) registry. Method This is a retrospective study. The primary outcome was overall survival (OS). Secondary outcomes were progression free survival (PFS), non-relapse mortality (NRM), relapse incidence (RI), acute Graft-versus-host disease (aGvHD) grade II-IV, chronic GvHD, neutrophil engraftment and GvHD-free relapse-free survival (GRFS). Competing risks analyses were performed to analyze NRM with competing event relapse, and aGvHD grade II-IV, chronic GvHD and neutrophil engraftment with competing events relapse and death. Univariable analyses were performed using the log-rang test for OS and PFS, while Gray's test was used for cumulative incidence (CI). Multivariable analyses were performed using the Cox proportional hazards regression model including age, ALL subtype, time from diagnosis to alloHSCT, disease status at alloHSCT, donor to patient CMV status, donor to patient sex, ATG use, myeloablative conditioning (MAC), TBI use. Results A total of 316 patients ≥ 60 years old transplanted for ALL from 2012 to 2022 in 36 participating centers were included in this study. Patient's characteristics are described in Table 1. With a median follow up of 34.5 months (IQR 29.5-38.8), 3-year OS was 46% (95% CI 40-53%) (Figure 1A) with only the disease status at transplant impacting negatively OS, 53% (95% CI 46-60%) in CR1, 32% (95% CI 21-49%) in CR2, 29% (95% CI 13-63%) in advanced disease, p=0.002 and the ALL subtype, 59% (95% CI 51-68%) in Ph+ ALL, 40% (95% CI 29-54%) in Ph- ALL, 34% (95% CI 20-55%) in T-ALL, 20% (95% CI 9-42%) in other/NA, p<0.001. 3-year PFS was 41% (95% CI 35-48%) (Figure 1B) with the disease status at transplant impacting negatively, 49% (95% CI 42-57%) in CR1, 26% (95% CI 16-42%) in CR2, 22% (95% CI 9-58%) in advanced disease, p<0.001, the ALL subtype, 51% (95% CI 42-61%) in Ph+ ALL, 41% (95% CI 31-54%) in Ph- ALL, 21% (95% CI 10-41%) in T-ALL, 21% (95% CI11-43%) in other/NA, p<0.001, year of HSCT worse < 2018, p=0.007, CMV -/- worse, p=0.033, absence of TBI worse, p=0.018. 3-year NRM was 23% (95% CI 18-28%) (Figure 1C) and none of the factors impacted it. 3-year RI was 36% (95% CI 31-42%) (Figure 1D) with the disease status at transplant impacting negatively, 29% (95% CI 23-36%) in CR1, 50% (95% CI 35-63%) in CR2, 56% (95% CI 26-77%) in advanced disease, p=0.0042, the ALL subtype, 26% (95% CI 19-34%) in Ph+ ALL, 43% (95% CI 31-54%) in Ph- ALL, 57% (95% CI 38-73%) in T-ALL, 42% (95% CI 25-59%) in other/NA, p=0.0064, year of HSCT worse < 2018, p=0.0216, CMV -/- worse, p<0.001, absence of TBI worse, p=0.0069, MRD worse, p=0.0111. 3-year GRFS was 30% (95% CI 25-37%) with the disease status at transplant impacting negatively, 35% (95% CI 28-43%) in CR1, 22% (95% CI 13-37%) in CR2, 23% (95% CI 9-59%) in advanced disease, p=0.029, the ALL subtype, 37% (95% CI 30-47%) in Ph+ ALL, 33% (95% CI 23-46%) in Ph- ALL, 15% (95% CI 7-32%) in T-ALL, 17% (95% CI 8-38%) in other/NA, p=0.0029, year of HSCT worse < 2018, p<0.001. CI of aGVHD grade II-IV was 33% (95% CI 28-38%), grade III-IV 11% (95% CI 8-15%), cGVHD 35% (95% CI30-41%), extensive cGVHD 21% (95% CI 16-26%).Multivariable analyses confirmed a worse OS and PFS for advanced disease, with a HR of 1.79 (95% CI 1.22-2.64), p=0.00322 and ALL subtype with a HR for other than Ph+ ALL of 1.99 (95%CI 1.42-2.79). Conclusion: This study suggests that alloHSCT is a reasonable option for elderly ALL patients without any impact of age but advanced disease and ALL subtype other than Ph+ ALL negatively influenced the outcome.

Complete Remission with Incomplete Count Recovery (CRi) Prior to sUCBT Is Associated with High Graft Failure in Acute Leukaemia Patients over 14 Years of Age

Recent studies have shown that measurable residual disease (MRD) has a definite impact on transplantation outcomes for acute leukaemia patients. However, the influence of complete remission with incomplete count recovery (CRi) prior to transplantation is rarely reported. Therefore, we retrospectively analysed 364 MRD-negative acute leukaemia patients who received single-unit unrelated cord blood transplantation (sUCBT). Among them, 90 patients were diagnosed with CRi. The cumulative incidence of neutrophil engraftment was lower for the CRi patients than for the CR patients. The cumulative incidences of platelet engraftment, 100-d non-relapse mortality (NRM), acute graft-versus-host disease(GVHD), chronic GVHD and the probabilities of 5-year overall survival, leukaemia-free survival and GVHD-free relapse-free survival were comparable. Among the patients older than 14 years (≥ 14), the CRi group was associated with decreased neutrophil and platelet engraftment compared to the CR patients (92.0% vs. 96.8%, 58.0% vs. 76.0%, P = 0.019, 0.018, respectively). Multivariate analysis of neutrophil engraftment in the patients ≥ 14 revealed that CRi,especially incomplete platelet recovery (CRp) prior to transplantation, were independent risk factors. Our study suggests that CRi is associated with an increased risk of graft failure for patients ≥ 14 after sUCBT, even after controlling for other risk factors.

Outcomes of Tcrαβ and CD19-Depleted Hematopoietic Stem Cell Transplantation from Matched, Mismatched Unrelated and Haploidentical Donors for Pediatric Patients with Hematological Malignancy: A Meta-Analysis

Introduction: TCR αβ+/CD19+ depletion in hematopoietic stem cell transplantation (HSCT) is an emerging graft manipulation technique to help overcome the HLA barrier in the mismatched or haploidentical transplant setting and reduce or prevent graft-versus-host disease. Limited research has explored the impact of various donor sources, and type of malignancy on the outcomes of TCR αβ+/CD19+ depleted HSCT for acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and myelodysplastic syndrome (MDS). Therefore, we performed a comprehensive meta-analysis of published clinical studies using individual patient data (IPD) to address this scientific gap. Methods: This meta-analysis combined patient-level data from studies involving AML/MDS and ALL patients treated with TCR αβ+/CD19+ depleted HSCT. By utilizing the IPDfromKM technique, we reconstructed time-to-event data from aggregated Kaplan-Meier curves, specifically focusing on overall survival (OS), disease-free survival (DFS), and GVHD-free, relapse-free survival (GRFS). Additionally, we conducted parallel meta-analyses to calculate the pooled incidences of GVHD, graft failure, mortality, as well as CMV and EBV reactivation, and sinusoidal obstruction syndrome (SOS) using aggregate data. All analyses were performed using STATA software. Our comprehensive literature search included publications up to May 2023, excluding studies with significant sample overlap. Results: The meta-analysis incorporated 817 children with AML/MDS or ALL from 12 studies. Successful primary engraftment was observed in 95% of patients (95% CI: 92 - 98), with an average time to neutrophil and platelet engraftment of 12 days. The incidence of acute GVHD grades I-II was 24% (95% CI: 14 - 34), while grades III and IV were 11% (95% CI: 3.0 - 0.18). Chronic GVHD was observed in 19% of patients (95% CI: 11 - 28). The relapse and graft failure rates were 25% (95% CI: 19 - 32) and 6% (95% CI: 2.0 - 9.0), respectively. The all-cause mortality was 34% (95% CI: 29 - 38), with HSCT-related mortality at 11% (95% CI: 8.0 - 13), while relapse-related mortality accounted for 22% (95% CI: 17 - 28). At a median follow-up of 2.55 years, the 1-year and 5-year OS rates were 74.7% (95% CI: 60.6 - 78.3) and 64.4% (95% CI: 59.9 - 68.5), respectively. No significant differences in OS were found between ALL and AML/MDS patients (HR= 0.99, 95% CI: 0.48 - 2.02, P=0.98) or between different donor types (Figure 1A). The DFS rates at 1- and 5-year were 72.8% (95%CI: 67.6 - 77.3) and 61.8% (95%CI: 56.1 - 67.0), respectively. No significant differences in DFS were observed between ALL and AML/MDS patients (HR = 0.74 95%CI: 0.48 - 1.14, P=0.17) or between different donor types (Figure 1B). The overall 1- and 5-year GRFS rates were 71.1% (95% CI: 64.1 - 77.4) and 63.0% (95% CI: 55.3 - 69.8), respectively. The overall incidence of CMV and EBV reactivation was 33% (95% CI: 19 - 46) and 16% (95% CI: 0 - 38), respectively. Conclusions: Our meta-analysis confirms the effectiveness and safety of TCRαβ and CD19-depleted HSCT for hematological malignancies, demonstrating high engraftment success, low graft failure, and a manageable incidence of acute and chronic GVHD. The consistently favorable outcome data across different donor types and malignancies support the broad applicability of this form of graft manipulation.

Outcome of Children with B-Cell Precursor Acute Lymphoblastic Leukemia (BCP-ALL) with Hypodiploidy or BCR-ABL1 Fusion Given Allogeneic Hematopoietic Stem Cell Transplantation (HSCT): Results from the Prospective Forum Study

Introduction: Hypodiploid karyotype (HYPO) and bcr-abl1 fusion (BCRABL) define high-risk BCP-ALL subtypes, with historically worse outcomes. Many front-line treatment protocols recommend allogeneic HSCT for these patients (pts), either in first complete remission (CR1) irrespective of response (adolescents/young adults with HYPO), if minimal residual disease (MRD) signals persist at specific time points (younger pts with HYPO and all pts with BCRABL), or following leukemic relapse. We have assessed the outcomes of BCP-ALL pts aged 4 to 18 years (y) with either HYPO or BCRABL who participated in the phase III ALL SCT PED FORUM study (EudraCT: 2012-003032-22) and underwent HSCT from either a matched sibling (MSD) or matched unrelated donor (MUD). Patients and Methods: Between 2014 and January 2023, 741 evaluable BCP-ALL pts were enrolled in FORUM (Table 1). HYPO was present in 61 pts, BCRABL in 82 pts, and neither lesion in 598 pts (NEITHER). 43/61 (70%), 40/82 (49%) and 215/598 (36%) pts with HYPO, BCRABL and NEITHER were in CR1, respectively (p= n.s.). Prior to HSCT, 82 of 101 HYPO/BCRABL pts with available MRD data were MRD negative by PCR and/or flowcytometry (<10-4). Total body irradiation (TBI) + VP16 was administered to 42 and 50 pts in the HYPO and BCRABL groups, respectively, while 18 HYPO and 30 BCRABL pts received non-TBI conditioning (busulfan or treosulfan + fludarabine and thiotepa, as per study protocol). Randomization determined allocation to TBI/non-TBI treatment arms until randomization closure in 03/2019, while treatment in some pts was dictated by lack of access to TBI, or contraindication to TBI in individual pts. An MSD was available in 14 (23%) and 24 (29%) HYPO and BCRABL pts, respectively. Notably, 24 out of 143 pts (17%) with HYPO/BCRABL received immunotherapy before HSCT (blinatumomab, inotuzumab ozogamicin, and/or CAR-T cells). Post-HSCT, 14 out of 82 BCRABL pts (17%) received a tyrosine kinase inhibitor (TKI), either prophylactically or pre-emptively. Results: With a median follow-up of three years post-HSCT, the 5-y probabilities of overall survival (OS) for pts with HYPO, BCRABL and NEITHER were 0.79±0.06, 0.83±0.05, and 0.74±0.02 (p=n.s.), while those of event-free survival (EFS) were 0.73±0.06, 0.65±0.07, and 0.61±0.02, respectively (p=n.s.). The 5-y cumulative incidence of relapse (CIR) for HYPO/BCRABL and NEITHER pts was 0.21±0.04 and 0.29±0.02 (p=0.036), and 5-y non-relapse mortality (NRM) was nearly identical for these groups (0.07±0.2 and 0.08±0.1). Among pts who received TBI, 5-y OS and EFS for HYPO, BCRABL, and NEITHER groups were 0.76±0.08 and 0.70±0.08, 0.89±0.05 and 0.70±0.10, and 0.80±0.03 and 0.71±0.03, respectively (p=n.s., Figure 1), while 5-y CIR and NRM post TBI were 0.15±0.06 and 0.11±0.05, 0.15±0.06 and 0.11±0.05, and 0.20±0.02 and 0.07±0.02, for the three groups, respectively (p=n.s.). The 3-y GvHD-free/relapse-free survival (GRFS) was similar between HYPO/BCRABL and NEITHER (0.60±0.06 and 0.58±0.03, respectively) and reached a plateau at 5-years (0.60±0.06 and 0.57±0.03, respectively). In subgroup analyses of pts in CR1 and >CR1, comparable outcomes were observed for HYPO, BCRABL, and NEITHER, hence results were not affected by the remission status. BCRABL and NEITHER pts receiving non-TBI conditioning had inferior outcomes (5-y EFS of 0.56±0.10 and 0.47±0.04, respectively) with a high 5-y CIR (0.36±0.09 and 0.43±0.04, respectively) as compared to those who received TBI. Similar 5-y OS and EFS were seen in HYPO pts whether receiving TBI (0.76±0.8 and 0.70±0.08) or chemo conditioning (83±0.09 and 83±0.09). Rates of NRM and acute/chronic graft-versus-host disease were similar in pts receiving TBI/ non-TBI conditioning and in BCRABL/HYPO vs. NEITHER pts. In multivariate analysis adjusted for CR status, conditioning and MRD, EFS did not differ between HYPO/BCRABL and NEITHER pts. Conclusions: Children receiving HSCT for treatment of BCP-ALL with either hypodiploidy or bcr-abl1 fusion showed outcomes comparable to BCP-ALL pts without these genetic lesions. CIR and EFS reached plateaus beyond 3 y post-HSCT, indicating that approximately two-thirds of these pts can be cured by HSCT with low rates of treatment-related mortality. Pts with BCRABL achieved favorable outcomes without the need for long-term or lifelong TKI therapy.