Post-transplant Cyclophosphamide Group Research Articles

Comparative outcomes of various transplantation platforms, highlighting haploidentical transplants with post-transplantation cyclophosphamide for adult T-cell leukaemia/lymphoma.

This study retrospectively compared outcomes of various allogeneic haematopoietic cell transplantation (allo-HCT) platforms in patients with adult T-cell leukaemia/lymphoma. Platforms included human leukocyte antigen (HLA)-haploidentical-related donors using post-transplant cyclophosphamide (PTCY), HLA-matched related donors (MRD), HLA-matched unrelated donors (MUD) and cord blood transplantation (CBT). Patients who underwent their first allo-HCT between 2016 and 2021 were included. Outcomes analysed were overall survival (OS), relapse and non-relapse mortality (NRM). Seven hundred patients were included (PTCY, n = 121; MRD, n = 91; MUD, n = 160; CBT, n = 328). With a median follow-up of 794 days for survivors, 2-year OS was 48.1% (PTCY), 48.8% (MRD), 48.4% (MUD) and 34.6% (CBT); the respective 2-year cumulative incidence of relapse was 37.1%, 47.5%, 33.9% and 45.1% and that of NRM was 24.2%, 19.8%, 24.7% and 27.3%. PTCY was associated with delayed platelet engraftment relative to MRD and MUD. There was no increase in the incidence of severe acute or chronic graft-versus-host disease. In the PTCY group, poor performance status was a significant predictor of inferior OS, and infused CD34+ cell numbers of less than 5 × 106/kg were associated with delayed neutrophil and platelet engraftment. These results suggest that allo-HCT with PTCY is a safe and effective platform for patients with adult T-cell leukaemia/lymphoma.

Clinical outcomes of three haploidentical transplantation protocols for hematologic malignancies based on data from the Chinese Bone Marrow Transplantation Registry Group.

This study aimed to demonstrate the clinical outcomes of granulocyte colony-stimulating factor (G-CSF)/antithymocyte globulin (ATG), posttransplantation cyclophosphamide (PTCy) and PTCy combined with lowdose ATG (PTCy with ATGlow)-based haploidentical transplantation protocols in patients with haematologic malignancies. The comparisons were conducted via propensity score matching (PSM) analysis to balance the basic characteristics among different groups and were based on the transplantation data reported to the Chinese Bone Marrow Transplantation Registry Group (CBMTRG) from January 2020 to December 2022. For each patient in the PTCy or PTCy with ATGlow group, patients (at a 1:2 ratio) from the GCSF/ ATG group were selected. In total, the PTCy group (n=122) was matched with G-CSF/ATG Group 1 (n=230), and the PTCy+ATGlow group (n=123) was matched with G-CSF/ATG Group 2 (n=226). Compared with those in the PTCy group, the incidences of 28-day neutrophil engraftment (P=0.005), 100- day platelet engraftment (P=0.002), median time to neutrophil engraftment (P.

Combination of reduced post-transplant cyclophosphamide and early tacrolimus initiation increases the incidence of chronic graft-versus-host disease in human leukocyte antigen-haploidentical peripheral blood stem-cell transplantation.

We evaluated the clinical impacts of the concurrent modification of post-transplant cyclophosphamide (PTCy) dose and tacrolimus (Tac)-initiation timing in 61 patients with human leukocyte antigen-haploidentical transplantation. Reduced-dose PTCy (80mg/kg) was associated with a higher incidence of moderate-to-severe chronic graft-versus-host disease (GVHD) than standard-dose PTCy (100mg/kg) (35.0%vs. 26.6%, p=0.053). Notably, early-initiation Tac (day -1) increased moderate-to-severe chronic GVHD than standard-initiation Tac (day 5) in the reduced-dose PTCy group (p=0.032), whereas Tac-initiation timing did not impact chronic GVHD in the standard-dose PTCy group. These data indicate that the combination of reduced-dose PTCy and early-initiation Tac can amplify chronic GVHD.

Comparable relapse incidence after unrelated allogeneic stem cell transplantation with post-transplant cyclophosphamide 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.

We compared relapse incidence (RI) post-unrelated transplantation with post-transplant cyclophosphamide (PTCy) versus no PTCy graft-versus-host disease (GVHD) prophylaxis, in 7049 acute myeloid leukemia (AML) patients in remission, 707 with PTCy, and 6342 without (No PTCy). The patients in the PTCy group were younger, 52.7 versus 56.6 years (p < .001). There were more 9/10 donors in the PTCy group, 33.8% versus 16.4% (p < .001), and more received myeloablative conditioning, 61.7% versus 50.2% (p < .001). In the No PTCy group, 87.7% of patients received in vivo T-cell depletion. Neutrophil and platelet engraftment were lower in the PTCy versus No PTCy group, 93.8% and 80.9% versus 97.6% and 92.6% (p < .001). RI was not significantly different in the PTCy versus the No PTCy group, hazard ratio (HR) of 1.11 (95% confidence interval [CI] 0.9-1.37) (p = .31). Acute GVHD grades II-IV and III-IV, were significantly lower in the PTCy versus the No PTCy group, HR of 0.74 (95% CI 0.59-0.92, p = .007) and HR = 0.56 (95% CI 0.38-0.83, p = .004), as were total and extensive chronic GVHD, HRs of 0.5 (95% CI 0.41-0.62, p < .001) and HR = 0.31 (95% CI 0.22-0.42, p < .001). Non-relapse mortality (NRM) was significantly lower with PTCy versus the No PTCy group, HR of 0.67 (95% CI 0.5-0.91, p = .007). GVHD-free, relapse-free survival (GRFS) was higher in the PTCy versus the No PTCy group, HR of 0.69 (95% CI 0.59-0.81, p = .001). Leukemia-free survival (LFS) and overall survival (OS) did not differ between the groups. In summary, we observed comparable RI, OS, and LFS, significantly lower incidences of GVHD and NRM, and significantly higher GRFS in AML patients undergoing unrelated donor-hematopoietic stem cell transplantation with PTCy versus No PTCy GVHD prophylaxis.

PTCy vs CNI–based GVHD prophylaxis in HLA-matched transplants for Hodgkin lymphoma: a study of the LWP of the EBMT

AbstractStudies comparing the efficacy of posttransplant cyclophosphamide (PTCy) to conventional calcineurin inhibitor (CNI)–based graft-versus-host disease (GVHD) prophylaxis regimens in patients with Hodgkin lymphoma (HL) are scarce. This study aimed to compare the outcomes of patients with HL undergoing hematopoietic stem cell transplantation (HSCT) from HLA-matched donors who received GVHD prophylaxis with either PTCy- or conventional CNI-based regimens, using data reported in the European Society for Blood and Marrow Transplantation database between January 2015 and December 2022. Among the cohort, 270 recipients received conventional CNI-based prophylaxis and 176 received PTCy prophylaxis. Notably, PTCy prophylaxis was associated with delayed hematopoietic recovery but also with a lower risk of chronic (25% vs 43%; P < .001) and extensive chronic GVHD (13% vs 28%; P = .003) compared with the CNI-based cohort. The 2-year cumulative incidence of nonrelapse mortality and relapse was 11% vs 17% (P = .12) and 17% vs 30% (P = .007) for PTCy- and CNI-based, respectively. Moreover, the 2-year overall survival (OS), progression-free survival (PFS), and GVHD-free, relapse-free survival (GRFS) were all significantly better in the PTCy group compared with the CNI-based group: 85% vs 72% (P = .005), 72% vs 53% (P < .001), and 59% vs 31% (P < .001), respectively. In multivariable analysis, PTCy was associated with a lower risk of chronic and extensive chronic GVHD, reduced relapse, and better OS, PFS, and GRFS than the CNI-based platform. Our findings suggest that PTCy as GVHD prophylaxis offers more favorable outcomes than conventional CNI-based prophylaxis in adult patients with HL undergoing HSCT from HLA-matched donors.

ATG or post-transplant cyclophosphamide to prevent GVHD in matched unrelated stem cell transplantation?

There is a high risk of GVHD and non-relapse mortality (NRM) after allogeneic stem cell transplantations (alloSCT) from unrelated donors. Prophylaxis with rabbit anti-thymocyte globulin (rATG) is standard in Europe but post-transplantation Cyclophosphamide (PTCy) is an emerging alternative. We analyzed outcomes of rATG (n = 7725) vs. PTCy (n = 1039) prophylaxis in adult patients with hematologic malignancies undergoing peripheral blood alloSCT from 10/10 antigen-matched unrelated donors (MUD) between January 2018 and June 2021 in the EBMT database. The provided P-values and hazard ratios (HR) are derived from multivariate analysis. Two years after alloSCT, NRM in the PTCy group was 12.1% vs. 16.4% in the rATG group; p = 0.016; HR 0.72. Relapse was less frequent after PTCy vs. rATG (22.8% vs. 26.6%; p = 0.046; HR 0.87). Overall survival after PTCy was higher (73.1% vs. 65.9%; p = 0.001, HR 0.82). Progression free survival was better after PTCy vs. rATG (64.9% vs. 57.2%; p < 0.001, HR 0.83). The incidence of chronic GVHD was lower after PTCy (28.4% vs. rATG 31.4%; p = 0.012; HR 0.77), whereas the incidence and severity of acute GVHD were not significantly different. GVHD-free relapse-free survival was significantly higher in the PTCy arm compared to the rATG arm (2 y incidence: 51% vs. 45%; HR: 0.86 [95% CI 0.75–0.99], p = 0.035). In the absence of evidence from randomized controlled trials, our findings support a preference for the use of PTCy in adult recipients of peripheral blood alloSCTs from MUD.

PTCy versus ATG as graft-versus-host disease prophylaxis in mismatched unrelated stem cell transplantation

There is an increased risk of GVHD and of non-relapse mortality (NRM) after allogeneic stem cell transplantations (alloSCT) when mismatched unrelated donors (MMUD) are used. In Europe, it is standard practice to use rabbit anti-thymocyte globulin (rATG) to reduce the high NRM and GVHD risks after MMUD alloSCT. As an alternative to rATG, post-transplantation Cyclophosphamide (PTCy) is in increasing clinical use. It is currently impossible to give general recommendations regarding preference for one method over another since comparative evidence from larger data sets is lacking. To improve the evidence base, we analyzed the outcome of rATG vs. PTCy prophylaxis in adult patients with hematologic malignancies undergoing first peripheral blood alloSCT from MMUD (9/10 antigen match) between Jan 2018 and June 2021 in the database of the European Society for Blood and Marrow Transplantation (EBMT). We performed multivariate analyses using the Cox proportional-hazards regression model. We included 2123 patients in the final analyses (PTCy, n = 583; rATG, n = 1540). p values and hazard ratios (HR) presented here are multivariate outcomes. Two years after alloSCT we found a lower NRM in the PTCy group of 18% vs. 24.9% in the rATG group; p = 0.028, HR 0.74. Overall survival in the PTCy cohort was higher with 65.7% vs. 55.7% in the rATG cohort; p < 0.001, HR 0.77. Progression-free survival was also better in the PTCy patients with 59.1% vs. 48.8% when using rATG; p = 0.001, 0.78. The incidences of chronic GVHD and acute GVHD were not significantly different between the groups. We found significantly lower NRM as well as higher survival in recipients of peripheral blood alloSCTs from MMUD receiving PTCy as compared to rATG. The results of the current analysis suggest an added value of PTCy as GVHD prophylaxis in MMUD alloSCT.

Post-transplant cyclophosphamide versus anti-thymocyte globulin after reduced intensity peripheral blood allogeneic cell transplantation in recipients of matched sibling or 10/10 HLA matched unrelated donors: final analysis of a randomized, open-label, multicenter, phase 2 trial

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis is not established after reduced intensity conditioning (RIC) hematopoietic stem cell transplantation (HSCT) from fully matched donors. This was a randomized, open-label, multicenter, phase 2 trial. All patients received a RIC regimen with fludarabine, intravenous busulfan for 2 days (Flu-Bu2), and a peripheral blood stem cell (PBSC) graft from a matched related or 10/10 HLA-matched unrelated donor. Patients were randomly assigned to receive anti-thymocyte globulin (ATG) 5 mg/kg plus standard GVHD prophylaxis or PTCy 50 mg/kg/d at days +3 and +4 plus standard GVHD prophylaxis. The primary endpoint was the composite endpoint of GVHD- and relapse-free survival (GRFS) at 12 months after HSCT. Eighty-nine patients were randomly assigned to receive either PTCy or control prophylaxis with ATG. At 12 months, disease-free survival was 65.9% in the PTCy group and 67.6% in the ATG group (P = 0.99). Cumulative incidence of relapse, non-relapse mortality, and overall survival were also comparable in the two groups. GRFS at 12 months was 54.5% in the PTCy group versus 43.2% in the ATG group (P = 0.27). The median time to neutrophil and platelet count recovery was significantly longer in the PTCy group compared to the ATG group. Except for day +30, where EORTC QLQ-C30 scores were significantly lower in the PTCy compared to the ATG group, the evolution with time was not different between the two groups. Although the primary objective was not met, PTCy is effective for GVHD prophylaxis in patients receiving Flu-Bu2 conditioning with a PBSC graft from a fully matched donor and was well tolerated in term of adverse events and quality of life. This trial was registered at clinicaltrials.gov: NCT02876679.

Graft-versus-host-disease prophylaxis with ATG or PTCY in patients with lymphoproliferative disorders undergoing reduced intensity conditioning regimen HCT from one antigen mismatched unrelated donor

Post-transplant cyclophosphamide (PTCY) has been introduced as graft-versus-host disease (GvHD) prophylaxis in mismatched and matched unrelated hematopoietic cell transplant (HCT). However, data comparing outcomes of PTCY or ATG in patients undergoing a 1 antigen mismatched HCT for lymphoproliferative disease are limited. We compared PTCY versus ATG in adult patients with lymphoproliferative disease undergoing a first 9/10 MMUD HCT with a reduced intensity conditioning regimen from 2010 to 2021. Patients receiving PTCY were matched to patients receiving ATG according to: age, disease status at transplant, female to male matching, stem cell source and CMV serology. Grade II-IV acute GvHD at 100 day was 26% and 41% for the ATG and PTCY group, respectively (p = 0.08). Grade III–IV acute GvHD was not significantly different between the two groups. No differences were observed in relapse incidence, non-relapse mortality, progression-free survival, overall survival and GvHD-relapse-free survival at 1 year. The cumulative incidence of 1-year extensive chronic GvHD was 18% in the ATG and 5% in the PTCY group, respectively (p = 0.06). In patients with lymphoproliferative diseases undergoing 9/10 MMUD HCT, PTCY might be a safe option providing similar results to ATG prophylaxis. Due to the limited number of patients, prospective randomized trials are needed.

Impact of post-transplant cyclophosphamide (PTCy)-based prophylaxis in matched sibling donor allogeneic haematopoietic cell transplantation for patients with myelodysplastic syndrome: a retrospective study on behalf of the Chronic Malignancies Working Party of the EBMT.

We retrospectively compared outcomes of 404 MDS patients undergoing 1st matched sibling donor allo-HCT receiving either PTCy-based (n = 66) or other "conventional prophylaxis" (n = 338; mostly calcineurin inhibitor + methotrexate or MMF). Baseline characteristics were balanced, except for higher use of myeloablative regimens in the PTCy group (52.3% vs. 38.2%, p = 0.047). Incidences of neutrophil (Day +28: 89% vs. 97%, p = 0.011) and platelet (Day +100: 89% vs. 97%, p < 0.001) engraftment were lower for PTCy-based. Day +100 cumulative incidences of grade II-IV and III-IV aGVHD, and 5-year CI of extensive cGVHD were 32%, 18% and 18% for PTCy-based and 25% (p = 0.3), 13% (p = 0.4) and 31% (p = 0.09) for the conventional cohort. Five-year OS (51% vs. 52%, p = 0.6) and GRFS (33% vs. 25%, p = 0.6) were similar between groups. Patients receiving PTCy had a trend to a lower cumulative incidence of relapse (20% vs. 33%, p = 0.06), not confirmed on multivariable analysis (p = 0.3). Although higher NRM rates were observed in patients receiving PTCy (32% vs. 21%, p = 0.02) on univariate analysis, this was not confirmed on multivariate analysis (HR 1.46, p = 0.18), and there was no resultant effect on OS (HR 1.20, p = 0.5). Based on these data, PTCy prophylaxis appears to be an attractive option for patients with MDS undergoing MSD allo-HCT.

Different Sources of Hematopoietic Stem Cell Transplantation in Patients with Thalassemia Major: Relationship between Immune Reconstitution, Graft-Versus-Host Disease, and Viral Infections

Objective: To compare the relationship among immune reconstitution, graft-versus-host disease (GVHD), and viral infections in three kinds of hematopoietic stem cell transplantation(HSCT) using different host sources for thalassemia major(TM) patients: matched unrelated donor (MUD) HSCT, haploidentical (Haplo) HSCT with post-transplant cyclophosphamide (PTCy)-based prophylactic therapy, and TCRαβ-T cell-depleted HSCT (TDH). Methods: A total of 191 TM patients in our center between October 2018 and June 2022 were included in this study, comprising three transplant groups: MUD group (n=56), PTCy group (n=45), and TDH group (n=90). Four-color flow cytometry was used to detect the proportions and absolute counts of lymphocyte subsets at the 12th month after transplantation for the three different donor types. The immune reconstitution was analyzed and compared with the occurrence of GVHD and virus infections. Results: 1. Immune Reconstitution: (1) The ratio of helper cells (CD3 +CD4 +)/cytotoxic T cells (CD3 +CD8 +) at the 12 months after transplantation was compared among the three groups. There were statistically significant differences between the TDH and PTCy groups, as well as between the TDH and MUD groups(P=022 and 0.011, respectively). No statistical difference was found between the PTCy and MUD groups (P=0.932). The CD4 +/CD8 + ratio in the TDH group recovered the fastest and had already returned to the normal reference range (0.7-2.7). (2) The comparison of B cells (CD3 -CD19 +) at the 12 months after transplantation showed statistically significant differences between the TDH and PTCy groups, as well as between the MUD and PTCy groups (P=0.049 and 0.034, respectively). No statistical difference was found between the TDH and MUD groups (P=0.447). The recovery of B cells was faster in the TDH and MUD groups, while it was slowest in the PTCy group. (3) The comparison of natural killer cells (NK cells) (CD3 -CD56 +) at the 12 months after transplantation showed statistically significant differences between the TDH and PTCy groups, as well as between the TDH and MUD groups (P=0.048 and 0.000, respectively). No statistical difference was found between the PTCy and MUD groups (P=0.366). The TDH group exhibited the fastest recovery of NK cells. 2. Chronic GVHD (cGVHD): (1) 7/90 cases (7.78%) of cGVHD appeared in the TDH group, 19/45 cases (42.22%) in the PTCy group, and 2/56 cases (3.57%) n the MUD group. (2) No statistical difference showed in the incidence of cGVHD between the TDH and MUD groups (P=0.500). There was a statistical difference in the incidence of cGVHD between the TDH and PTCy groups (P=0.000), as well as between the MUD and PTCy groups (P=0.000). 3. Viral Infection: (1) 22/90 cases (24.44%) of viral infection occurred in the TDH group, 7/45 cases (15.56%) in the PTCy group, and 6/56 cases (10.71%) in the MUD group. (2) Among the 90 cases of TDH group, the CD4/CD8 ratio at the 6 months after transplantation was 0.41±0.24 in the 22 cases with viral infection and 0.69±0.40 in the 68 cases without that. There was a statistical difference in the mean CD4/CD8 ratio between the two divisions in the TDH group (P=0.013). Conclusion:The TDH group exhibited faster immune reconstitution compared to the other two groups, especially in terms of CD4/CD8 ratio, B cells, and NK cells. This may be related to two special factors for patients underwent TDH in our center: a rather high average infusion of CD34 cells (30×10 6/kg) , and the preservation of γδ cells, B cells, and NK cells with the removing of TCRαβ-T cells in the TDH treatment protocol. The TDH and MUD groups showed a lower incidence of cGVHD, while the PTCy group had a higher incidence. The occurrence of viral infection in the TDH group was 24.44%. Also, the lower a CD4/CD8 ratio at the 6 months after transplantation, the higher the incidence of viral infection. Table 1. The Absolute Counts of Lymphocyte Subsets at the 12th Month after Transplantation

Impact of Post-Transplant Cyclophosphamide (PTCY)-Based Prophylaxis in Matched Sibling Donor Allo-HCT for Patients with Myelodysplastic Syndrome: A Study on Behalf of the Chronic Malignancies Working Party of the EBMT

Background Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only potentially curative treatment option for patients with myelodysplastic syndrome (MDS). The use of PTCY for GVHD prevention is becoming increasingly prevalent across donor types/transplant platforms. However, limited studies have evaluated the efficacy and safety of using PTCY in patients with MDS undergoing matched sibling donor (MSD) allo-HCT. We hereby compare the outcomes of PTCY-based versus (vs.) conventional GVHD prophylaxis in a contemporaneous cohort of MDS patients undergoing MSD allo-HCT from the EBMT registry. Methods A total of 404 MDS patients undergoing first MSD peripheral blood allo-HCT between 2014 and 2020 in 52 participating centers, receiving either PTCY or other GvHD prophylaxis, were included. Primary outcomes were overall survival (OS), progression free survival (PFS), GVHD-free/RFS (GRFS), competing risks analyses for relapse (CIR), non-relapse mortality (NRM), and GVHD. The main comparison was PTCY vs. other types of GvHD prevention. Cox regression analyses with predefined covariates were used to obtain adjusted effect estimates of PTCY in post-transplant results.- Results The median age at allo-HCT was 57 years (IQR 49-62), 66 patients (16.3%) received PTCY, 338 (83.7%) received other prophylaxis. As reported in Figure 1, patient characteristics, disease risk, and pre-transplant status were balanced between the two cohorts. The majority of transplant characteristics were also analogous except for the proportion of adults receiving myeloablative regimens, which was higher in the PTCY group (52.3% vs. 38.2%, P=0.047). PTCY was combined with two additional immunosuppressant agents in 66.7% of the cases, with one additional immunosuppressive drug (generally calcineurin inhibitors (CNI)) in 31.8%, and administered as a single agent in only 1 (1.5%) case. Other prophylaxis mainly combined CNI with either mycophenolate mofetil or methotrexate, and in 162 (47.9%) of the cases, anti-thymocyte globulin was also administered. Post-transplant complications and outcomes are shown in Figure 1. Incidences of Day +28 neutrophil (68% vs. 97%, P=0.011) and platelet (71% vs. 92%, P&amp;lt;0.001) engraftment were lower in patients who received PTCY. The day +100 cumulative incidences (CI) of grade II-IV and III-IV aGVHD, and 5-year CI of extensive cGVHD were 32% (21-43%), 18% (9-27%) and 18% (9-28%) for patients who received PTCY, and 25% (20-30%; p=0.3), 13% (10-17%; p=0.4), 31% (26-36%; p=0.09) for those who did not. The 5-year CIs of cardiac and pulmonary toxicities were similar in both groups (23% (6-40%) vs. 19% (12-25%) (p=0.6) and 23% (8-38%) vs. 27% (21-34%) (p=0.6) in PTCY vs others, respectively). At 5-years after allo-HCT, the estimated OS (51% (39-64%) vs. 52% (46-58%), p=0.6), PFS (48% (36-61%) vs. 46% (40-52%), p=0.9), and GRFS (33% (21-45%) vs. 25% (20-30%), p=0.6), were similar between the two study groups. Nevertheless, patients who received PTCY tended to have lower CIR (20% (10-29%) vs. 33% (28-38%) (p=0.06)), but higher NRM rates (32% (20-43%) vs. 21% (16-25%), p=0.09) than the rest. Next, we performed a multivariable analysis (MVA) of OS, PFS, NRM and CIR (Figure 1). The results observed in the MVA confirmed that using PTCY in patients with MDS undergoing MSD allo-HCT resulted in comparable OS (HR 1.23 (0.77-1.97), p=0.4) and RFS (HR 1.13 (0.73-1.77), p=0.6) to conventional prophylaxis. Furthermore, the diagnosis of a high or very high-risk MDS (according to IPSS-R), and the presence of TP53 mutation at diagnosis were independent predictors of worse post-transplant outcomes. In addition, PTCY-based prophylaxis was associated with a higher NRM (HR 1.79 (1.07-2.98), p=0.03) when adjusted by variables known to be clinically relevant for NRM. Conclusion The use of PTCY in adults undergoing MSD allo-HCT for MDS resulted in comparable OS and RFS rates to conventional GVHD prophylaxis. Allo-HCT performed with PTCY was associated with a longer time to engraftment and comparable incidences of clinically relevant aGVHD. Of note, utilization of PTCY was associated with a non-significant trend to a lower incidence of extensive cGVHD. Furthermore, although a non-significant trend to lower rates of relapse were observed in allo-HCTs performed using PTCY, it use was associated with a higher risk for NRM. Further evaluation of PTCY in the MSD setting for MDS is required.

Post-transplant сyclophosphamide after matched donor hematopoietic stem cell transplantation in children with acute leukemia.

The data on post-transplant cyclophosphamide (PTCy) in pediatric acute leukemia after matched allo-HSCT are limited to case series. The present study aimed to assess the results of PTCy-based GVHD prophylaxis in a large cohort of children with acute leukemia after matched allo-HSCT. A retrospective analysis of 190 pediatric patients with acute leukemia who had a first allograft between 2008 and 2020 from a matched sibling donor (MSD) or matched unrelated donor (MUD) was carried out. In the MSD setting, GVHD prophylaxis consisted of PTCy alone (n=28) for the study group, and calcineurin inhibitor (CNI)±antimetabolite (n=30) for the control group. In MUD setting, most patients in the study group received GVHD prophylaxis with PTCy+CNI+mycophenolate mofetil (n=42, 66.7%) or PTCy+CNI+sirolimus (n=12, 19%). All patients (n=69) in the control group received ATG+CNI+antimetabolite. After MUD allo-HSCT, the incidences of acute GVHD grade III-IV and moderate/severe chronic GVHD were significantly lower in the PTCy group compared to control (6.6%vs. 35.0% and 12.7%vs. 47.1%, respectively, p<.0001). Five-year GVHD-free, relapse-free survival (GRFS) after MUD allo-HSCT was higher in the PTCy group compared to control (35.1%vs. 7.3%, p<.0001). At the same time, there was no significant difference between both groups after MSD allo-HSCT. In pediatric acute leukemia, PTCy-based GVHD prophylaxis for MUD allo-HSCT is a feasible and effective option that results in a low incidence of GVHD. Compared to the ATG-based approach, PTCy provides better control of GVHD in children. In pediatric allo-HSCT from MSD, PTCy demonstrates comparable effectiveness to conventional GVHD prophylaxis.

Dynamics of Immune Reconstitution after Unrelated Allogeneic Transplantation with Post-Transplantation Cyclophosphamide Compared to Classical Immunosuppression with ATG

Introduction: Post-transplant cyclophosphamide (PTCY), in hematopoietic stem cell transplantation (HSCT), is responsible for the success of haploidentical stem cell transplantation and is also being used in matched transplants such as unrelated transplants, with promising outcomes in graft versus host disease (GVHD). However, we lack data on immune reconstitution with this type of immunosuppression, especially in unrelated transplantation. Immune reconstitution is directly involved with post-transplant morbidity and mortality, being related to GVHD, relapses and infections, such as cytomegalovirus (CMV). Objectives: To evaluate global and CMV-specific immune reconstitution after unrelated donor HSCT, comparing the use of thymoglobulin (ATG) or PTCY protocol. Methods: We prospectively included patients undergoing first unrelated donor HSCT with ATG, methotrexate and tacrolimus or PTCY (50mg/Kg D+3 and D+4), mycophenolate mofetil (MMF) and tacrolimus with patient and/or donor CMV IgG positive. Immune reconstitution analyzes were performed by flow cytometry and CMV-specific recovery by ELISPot technique on days +30, +60, +90 and +180 post HSCT. Results: Thirty-six patients were included in this study, 20 in the ATG group and 16 in the PTCY group (table 1). Only 2 patients were 9x10 match, and the others were 10x10 match. All patients were submitted to preemptive strategy of CMV treatment, without the use of letermovir. Regarding clinical outcomes, neutrophilic engraftment was earlier with ATG (median of 12 days), compared to PTCY (median of 16 days) (p=0.0001). There was no difference between the groups in terms of length of hospital stay (median 33 days in both groups), CMV reactivation (70% in ATG and 75% PTCY, p=0.98), acute GVHD grades II to IV (p=0.26) or grades III-IV (p=0.56), and chronic GVHD (p=0.45), as well as relapse (p=0.3), non relapse mortality (p=0.77) and overall survival (p=0.4). Regarding immune reconstitution we observed an initial expansion of monocytes and NK lymphocytes in both groups and a higher increase in CD8+ T lymphocytes was evidenced, with an inversion of the CD4/CD8 ratio (CD4 14.9% vs 15.5% p=0.9 and CD8 49.7% vs 54.5%p=0.5 in ATG and PTCY respectively). We identified a CD4+/CD8+ double-positive T cell (DP) population, which was higher in PTCY group compared to ATG on days +30 (3.5% vs 10.2%, p=0.009), +90 (3.1% vs 12% p= 0.01) and +180 (5.2% vs 13%, p=0.007, in ATG and PTCY respectively ). On day +30 there were higher proportion of T cells (19.9% vs 9.6% p=0.004), B cells (0.76% vs 0.2%, p=0.006) and NK cells (19.2% vs 8.6% p=0.006) in ATG group compared to PTCY and monocytes were higher in PTCY (31.7 vs 44.5%, p=0.02). On day +180 the proportion of B cell were higher in PTCY (6.1% vs 16.6% p=0.014) and the NK cells were higher in the ATG (22.4% vs 14.7% p=0.021) (Figure 1), with higher CD56dim population in ATG group (46% vs 33.6% p=0.0079), while in PTCY there were a higher NK population CD56high on day +60 (40.3% vs 61%, p=0.014). We identified a peripheral expansion of a CD56negCD16posNKG2Dpos NK cell population, which was higher in the PTCY group on day +180 (3.7% vs 13.2% p=0.017). Regarding CMV-specific immune response, we found no difference between the groups on days +30 (5 vs 5 spots/10 4 PBMC p=0.41), +60 (10 vs 6 spots/10 4 PBMC p=0.38), +90 (13 vs 4 spots/10 4PBMC p=0.33) or +180 (7 vs 6 spots/10 4 PBMC p=0.57). Conclusions: In the context of unrelated HSCT, we found no difference in CMV-specific immune response with the use of PTCY or ATG protocol. Post-transplant immunosuppression with PTCY compared to ATG protocol is related to lower levels of T cells, NK cells and B cells on day +30 and later neutrophil engraftment, but with a higher proportion of double positive T cells on days +30, +90 and +180 and a higher proportion of B cells on day +180. At 6 months after transplantation, a proportionately lower number of NK cells, but higher proportion of CD56negCd16posNKG2D NK population was observed in the PTCY group.

Early Prognostic Biomarkers of Non-Relapse Mortality in Allogeneic Mismatched Unrelated Hematopoietic Cell Transplantation

Introduction A major challenge in allogeneic hematopoietic cell transplantation (HCT) has been advancing outcomes for individuals lacking a fully matched donor who require a mismatched unrelated donor (MMUD) HCT. Recently, the 15-MMUD study demonstrated encouraging results for post-transplant cyclophosphamide (PT-Cy)-based prophylaxis in MMUD recipients (Shaw, Jimenez, JCO 2021). Our retrospective analysis confirmed improvement in MMUD survival with PT-Cy compared to historical anti-thymocyte globulin (ATG)/calcineurin-based regimens (Jimenez, Blood Adv 2022). Elevations of plasma biomarkers such as Stimulation-2 (ST2) have demonstrated increased risk of non-relapse mortality (NRM) and GVHD, however these have not been validated in the MMUD setting. Here, we carried out a pilot study to determine if biomarker analysis of ST2, Chemokine ligand-9 (CXCL-9), and Regenerating islet-derived 3-α (REG3α) at Day 14 (D14) and 30 (D30) can identify patients at higher risk for NRM after MMUD HCT. Methods Patients with banked samples and underwent MMUD HCT with either ATG or PT-Cy as GVHD prophylaxis at the University of Miami between 2016 - 2020 were included. Enzyme-linked immunosorbent assays for ST2, CXCL-9, and REG3α were performed in batches on cryopreserved plasma. Descriptive statistics of demographic variables were compared using chi-squared, Fisher's exact, or Wilcoxon rank sum tests. ST2 values were treated as continuous variables, and CXCL-9 was dichotomized due to frequent values below the lower limit of detection. Cumulative incidences of NRM were analyzed with relapse as a competing risk. Time-dependent receiver operating curves (ROC) were constructed and Area Under the ROC Curve (AUC) calculated. Youden's index was used to select optimum thresholds for each biomarker. Results We included 47 patients (ATG: 23; PT-Cy: 24). The PT-Cy group had more bone marrow graft representation (50% vs 22%, p = 0.04) and more donors mismatched at &amp;gt;1 HLA-locus (29% vs 0%, p&amp;lt;0.01). Median follow up was 746 days (range 44-1968). Point estimate of overall survival at 2 years was 35% (95% CI 20-61) for ATG and 71% (95% CI 55-92) for PT-Cy (p=0.02). Median overall survival was estimated at 413 days among ATG patients and could not be estimated for PT-Cy patients. The cumulative incidence of NRM at 2-years was 30% (95% CI 13-51%) for ATG and 17% (95% CI 5-35%) for PT-Cy (p=0.03). Among all patients, ST2 was prognostic for NRM using time-varying covariates including combined D14 and D30 (D14+30) with a HR of 2.14 (95% CI 1.04-4.39, p = 0.04). The D14+30 ROC to predict NRM at 1-year using ST2 showed an AUC of 0.83 (95% CI 0.66-1). D+14 thresholded ST2 value maximizing Youden's index of ≥79.89 ng/mL was discriminative for 1-year NRM (p=0.002) (Fig. 1). Additionally, combination of CXCL-9 to ST2 could optimize the prognostic value when compared to ST2 alone: HR at D14+D30: 3.82 (95% CI 1.01-14.47, p=0.048) with an improved AUC of 0.9 (95% CI 0.79-1) (Fig. 2). REG3α did not significantly add to the AUC. Although limited by sample size, we explored the association by GVHD prophylaxis (ATG or PT-Cy). First, in the ATG group, the D14 ST2 value that maximized thresholded Youden's index of 61.39 ng/mL was predictive of 1-year NRM (p=0.04). Similarly, the D+30 ST2 values of 148.06 ng/mL was predictive of NRM (p&amp;lt;0.001). The AUC for prediction of 1-year NRM for Second, in the PT-Cy group, elevations of D30 ST2 were prognostic of 1-year NRM with HR 15.05 (95% CI 1.77-27.83, p=0.01). Consequently, the AUC for prediction of 1-year NRM for D30 ST2 was 0.92 (95% CI 0.77-1) and for ST2 + CXCL-9 was 0.96 (95% CI 0.86-1). Conclusions This pilot study suggests that after MMUD HCT, D14 and D30 biomarkers are prognostic for NRM across GVHD prophylaxis platforms. Importantly, we find that ST2 maintains its prognostic capacity in the increasingly popular PT-Cy group. This supplements what we previously reported in the haploidentical and matched unrelated donor PT-Cy setting (Kanakry, Haematologica 2017). Biomarker combination ST2 + CXCL-9 showed improved AUC over ST2 alone, and the composite D14+30 timepoint may have additive utility over a single timepoint. While the optimal time for biomarker collection is unknown, our data suggests D14 had value for ATG-treated patients, whereas D30 may be more important in the PT-Cy-treated group. A validation cohort is being assembled for PT-Cy based MMUD HCT.

Risk Factors for CMV Infection, Including HLA Disparity and Ptcy Transplant in the Era of Letermovir Prophylaxis

Reports suggest that post-transplant cyclophosphamide (PTCy) for haploidentical and HLA-matched sibling donor allogeneic stem cell transplant (allo-SCT) is associated with a higher incidence of cytomegalovirus (CMV) infection than calcineurin inhibitor (CNI) for HLA-matched sibling donor allo-SCT. Prophylactic letermovir has been shown effective for CMV seropositive patients, based on the data mostly before the FDA approval of letermovir (2017). We reevaluated the risk of CMV infection in PTCy transplants. We retrospectively analyzed 175 patients after allo-SCT between May 2019-May 2022). CMV infection was monitored at least for the first year by serostatus, viral load over 500 IU/mL, and/or evidence of CMV end-organ disease. Univariate and multivariate Cox regression analyses were used for the factors, including CMV serostatus, use of letermovir, GVHD prophylaxis, and HLA disparities, to affect the risk of CMV infection and graft-versus-host disease (GVHD)-free relapse-free survival (GRFS). Cumulative incidence curves were used to visualize the incidence of CMV infection stratified by HLA match and PTCY use. A landmark analysis at Day +100 was used for GRFS, where patients who had CMV infection beyond Day +100 (N=13) were assigned to the no-infection group. Of the 175 patients, 108 received HLA-matched donors with GVHD prophylaxis, either CNI (N=70) or PTCy (N=38), while 67 received HLA mismatched donors with either CNI (n=6) or PTCy (N=66) ( Table). Letermovir was given to 137 patients (CMV IgG positive N=130, negative N=7) but not to 38 patients (CMV IgG positive N=12, negative N=26). CMV infection occurred in 28 patients (CMV IgG positive N= 28, CMV IgG negative N=0) before or after Day +100 (N=15 or N=13, respectively). CMV IgG positive recipients not receiving letermovir demonstrated a higher risk of infection by Day +100 than those receiving letermovir (Hazard ratio (HR) 10.1 (95% confidence interval (CI) 3.6-28.6), p&amp;lt;0.01). All 13 infections after Day +100 occurred after the cessation of letermovir (median: 82.9 days after cessation). On univariate analysis, PTCy and HLA mismatch donors increased the risk of CMV infection. The risk of infection by Day +100 increased with PTCy (p=0.07). The risk of infection after Day +100 increased with HLA mismatch donors (p=0.05). In addition, it was confirmed that HLA mismatch allo-SCT with PTCy increased the risk of CMV infection over matched allo-SCT with CNI ( Figure, HR 4.6 (95% CI 1.6-11.9), p&amp;lt;0.01), while HLA match allo-SCT with PTCy did not (p=0.3) (Figure 1). The trend was similar when analyzed only in the case of CMV infection by Day +100 (p&amp;lt;0.05) and after Day +100 (p=0.1). In the 130 CMV IgG seropositive patients who received letermovir, multivariate analysis showed that HLA mismatch donors with PTCy increased the risk of CMV infection over HLA match allo-SCT with CNI. When analyzed only for acute myeloid leukemia, acute lymphoblastic leukemia, and myelodysplastic syndrome with letermovir (N=91), HLA mismatch transplant with PTCy increased the risk of CMV infection over HLA match transplant with CNI (p=0.05), but not for HLA match transplant with PTCy. Landmark analysis demonstrated better GRFS in the PTCy group than the CNI group and in patients who received PTCy with CMV infection than those who received CNI without CMV infection (p&amp;lt;0.01). PTCy increased the incidence of CMV infection in HLA mismatch allo-SCT by D+100 but not HLA match allo-SCT in the era of letermovir prophylaxis. Patients with PTCy transplant who overcome CMV infection have improved GRFS, possibly due to the increased graft-versus-leukemia effect. Further analysis is required to confirm the difference in the incidence of CMV infection between HLA match and mismatch transplant with PTCy and to assess the significance of late CMV (after Day +100) infection on GRFS.

Low-Dose ATG Has the Same Risk of CMV Reactivation after Allogeneic PBSCT As Ptcy, but Letemovir Is Effective in Preventing CMV Reactivation

[Introduction] Allogeneic peripheral blood stem cell transplantation (allo-PBSCT) is a curative treatment for hematological malignancies but has a risk of a chronic graft-versus-host disease (GVHD) compared to other donor sources. Post-transplant cyclophosphamide (PTCY) has been spread rapidly worldwide from HLA haploidentical-SCT (Haplo-SCT) to HLA matched-SCT. Although PTCY was theoretically thought to preserve non-alloreactive T cells which can contribute to fight infection, recent studies showed that PTCY was associated with the increased incidence of cytomegalovirus (CMV) infection. Letermovir (LTV), a novel anti-CMV agent, was useful for the prevention of CMV reactivation after SCT including Haplo-SCT using PTCY. On the other hand, low-dose antithymocyte globulin (ATG) is an alternative and useful option for GVHD prophylaxis in allo-PBSCT and often used in Japan. However, the risk of post-transplant CMV reactivation and the protective effect of LTV when using low-dose ATG remain to be elucidated. [Methods] We retrospectively analyzed 222 recipients who received allo-PBSCT using PTCY or low-dose ATG at Hokkaido University Hospital from January 2013 to July 2021. Of the 121 patients who underwent PBSCT with PTCY, 69 (all patients underwent Haplo-PBSCT) were without LTV prophylaxis and 52 (34 patients, Haplo-PBSCT) were with LTV. On the other hand, of the 101 patients who underwent PBSCT with low-dose ATG, 66 (12 patients, Haplo-PBSCT) were without LTV and 35 (2 patients, Haplo-PBSCT) were with LTV. LTV was administered on the day 0 at a dosage of 480 mg daily. All patients were monitored for CMV reactivation by using the anti-CMV pp65 monoclonal antibody HRP-C7 assay at least weekly from neutrophil engraftment to discharge and after discharge monthly until day 180 after SCT. CMV reactivation was defined as the start of CMV preemptive therapy, generally initiated when there are 2 or more CMV antigen positive cells per 50000 white blood cells. Moreover, CMV disease was defined by organ dysfunction attributable to CMV. [Results] Baseline characteristics of the patients are summarized in Table 1. Although more patients in ATG group compared to PTCY group received myeloablative conditioning regimen significantly, there was no significant difference between the groups in terms of sex, age, underlying disease, disease risk at SCT, and CMV serostatus. GVHD prophylaxis in PTCY consisted of CY (40-50 mg/kg on day 3 and 4), tacrolimus (from day 5), and mycophenolate mofetil (from day 5), whereas that in ATG consisted of ATG at a total dose of 2-3 mg/kg around day -2, tacrolimus (from day -1) and short-term methotrexate. LTV prophylaxis significantly reduced the cumulative incidence of CMV reactivation at 180 days after SCT in PTCY group (69.6% without LTV vs. 22.4% with LTV, p&amp;lt;0.001) and ATG group (62.6% without LTV vs. 18.9% with LTV, p&amp;lt;0.001; Figure 1.). Importantly, although CMV disease were occurred in 2 patients in PTCY (1 gastritis and 1 retinitis) and 8 focuses in 7 patients (3 pneumoniae, 3 enteritis, 1 retinitis, and 1 glossitis) in ATG without LTV prophylaxis, none of the patients receiving LTV developed CMV disease in both group. Moreover, LTV did not affect overall survival, the cumulative incidence of non-relapse mortality, relapse, acute GVHD, and engraftment of neutrophil and platelet. Interestingly, the cases of early CMV reactivation within 100 days after SCT under LTV prophylaxis was significantly more frequent in ATG than in PTCY (p=0.0345). [Conclusion] CMV reactivation occurred with similar frequency after allo-PBSCT with low-dose ATG as after that with PTCY. LTV was effective for prevention of CMV reactivation in both GVHD prophylaxis methods. CMV breakthrough reactivation may be likely to occur in PBSCT with low-dose ATG compared to that with PTCY even under LTV prophylaxis, and careful CMV monitoring may be required.

Allogeneic Hematopoietic Cell Transplantation with Sequential-Based Conditioning in Refractory / Relapsed Acute Myeloid Leukemia: Experience from a Single Institution

INTRODUCTION: Despite improvements in the treatment and outcomes of patients with acute myeloid leukemia (AML), in nearly 10-20% of the cases, a morphological remission (CR) after administrating induction regimens is not achieved. In other cases, and despite initial CR, early disease relapse may occur, with only a minority of patients durably benefiting from salvage regimens. Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative strategy for patients with relapsed / refractory (R/R) AML. However, the prognostic of these patients after allo-HCT remains dismal, with reported survival rates ranging from 20% to 35% in different publications. Allo-HCT using peripheral blood and sequential-based conditioning regimens has been the transplant platform used at our institution for R/R AML during the last decade. During the study period the use of post-transplant cyclophosphamide (PTCY) combined with tacrolimus (TK) has been implemented on this allo-HCT setting. This study evaluates the results obtained from a single institution obtained from using sequential allo-HCT for patients with R/R AML, and the effectiveness of having implemented the use of PTCY in this type of transplant. Very few studies have evaluated the safety of including PTCY-based in sequential-based conditioning allo-HCTs. METHODS: This study includes the 21 patients with R/R AML who underwent allo-HCT with sequential-based conditioning regimens at our institution between 2011 and 2022. Retrospective data were collected during June 2023. Sequential regimens combined fludarabine (150 mg/m2), cytarabine (2 g/m2 x 5 days), and idarubicin (12 mg/m2 x 3 days) chemotherapy with low doses of Bu (n=3), melphalan (n=17), or treosulfan (n=1). Six adults transplanted after November 2016 received PTCY (50mg/kg/24h) on day +3 and +4 followed by TK from day +5 to day +90 for GvHD prevention. RESULTS: The main baseline characteristics of the study cohort and according to the GVHD prophylaxis are shown in Table 1 . The median age was 53 years (range 31-68), 11 (52%) patients were males, and all patients had R/R AML after having received at least one line of induction chemotherapy with curative intent. Fourteen (66.7%) patients received grafts from HLA-matched donors, and 7 (33.3%) from 9/10 HLA mismatched unrelated donors (MMUD). Baseline characteristics between patients who received PTCY and those who did not were balanced, except for the proportion of allo-HCT performed from MMUD which was higher in the PTCY group (66.7% vs. 20.0% p=0.03). Post-transplant results are shown in Table 2. All patients engrafted (100%). Patients who received PTCY experienced similar median of days to neutrophil engraftment (18 vs. 15 days, P=0.103) and a longer median of time to platelet engraftment (25 vs. 13 days, P=0.046). The day +100 cumulative incidences (CI) of grade II-IV and III-IV aGVHD, and 2-year CI of moderate/severe cGVHD were 33.3%, 0% and 0% for patients who received PTCY-TK, and 40% (p=0.823), 33% (p=0.118), and 40.4% (p=0.099) for those who did not. During the first 2-years after allo-HCT, 8 (38%) out of 21 patients died and 7 (21%) relapsed. The main causes of death were relapse (n=4, 19%) and infection (n=2, 9.5%), and the 2-year OS, PFS, NRM and CIR were 61.5%, 51.9%, 14.3%, and 33.3%. As shown in Table 2 patients who received PTCY had comparable rates of OS (2-y: 50.0% vs. 66.7%, p=0.903) and RFS (2-y: 50.0% vs. 53.3%, p=0.873) and those who did not. In addition, and although no patient who received PTCY died secondary to transplant-related toxicity (2-y 0 vs. 20%, p=0.254), a non-significant trend to higher cumulative incidence of relapse (2-y: 50.0% vs. 26.7%, p=0.282) was observed in this group of patients. Lastly, a non-significant trend to higher GRFS was documented in patients who received PTCY (2-y: 50.0% and 25.0%, p=0.266). CONCLUSIONS: At our institution, 50% of the patients with R/R AML going thought allo-HCT performed using sequential-based conditioning regimens survived after two years. The implementation of PTCY as part of the GVHD prophylaxis results decreased rates clinically relevant GVHD and NRM, resulting on a trend to better GRFS. Although the results provided by this analysis suggest that using PTCY in this allo-HCT is safe and effective, caution is still recommended considering the trend to higher relapse rates observed among these patients and the limited sample size.

Post-Transplant Cyclophosphamide (PTCY) Compared to ATG in Patients with Myelodysplastic Neoplasms Allografted with an Unrelated Donor: A Registry Study of the Chronic Malignancies Working Party of the EBMT

Background Prospective randomized trials have reported a benefit for ATG-based GVHD prophylaxis in the setting of allogeneic hematopoietic stem cell transplantation (alloHSCT) with an unrelated donor (UD). However, the best GVHD prophylaxis has been recently challenged by the use of PTCY, first in haplo-identical transplant and then in HLA mismatched or matched unrelated transplantation. We here present the outcomes of PTCY vs ATG as GVHD prophylaxis in MDS patients from the EBMT registry transplanted with an unrelated donor. Method A total of 969 patients transplanted from 2012 to 2019 in 92 participating centers, receiving either PTCY or ATG, were included in this study. The primary outcomes were progression free survival (PFS) and overall survival (OS). Competing risks analyses were performed to analyze non-relapse mortality (NRM) with competing event relapse, and acute GvHD grade II-IV, chronic GvHD and neutrophil engraftment with competing events relapse and death. Cox proportional hazards regression with a predefined covariate constellation (age, IPSS-R cytogenetics, donor HLA matching, age, hypomethylating agents (HMA) prior to transplantation, comorbidity score and MDS classification (MDS with or without excess blast, EB) was used to obtain adjusted effect estimates of ATG compared to PTCY for OS and PFS. Results Overall, 214 patients received PTCY and 755 received ATG as GVHD prophylaxis for UD alloHSCT. Patients of the ATG group were older (60.1 year-old [IQR: 50.6-65.2] vs 57.2 year-old [IQR: 46.4-61.1], p=0.008). Disease characteristics were similar in both group: there were a total of 583 MDS with EB at diagnosis, 510 MDS-EB at transplantation, and 207 patients transformed into AML. Among patients with available data for IPSS-R at MDS diagnosis (n=760) 44 (5.8%) were Very Low, 114 (15%) Low, 209 (27.5%) Intermediate, 232 (30.5%) High and 161 (21.2%) Very High. Patients of the PTCY group received more frequently HMA before transplantation (72.4% vs 57.3%, p=0.001) and were preferentially transplanted from an HLA mismatched 9/10 donor (37.9% vs 21.6%, p&amp;lt;0.001). Conditioning regimen was more frequently myeloablative in the PTCY group (55.4% vs 38.7%, p&amp;lt;0.001). Neutrophil engraftment at 28 days was significantly better with ATG (93% vs 84%, p&amp;lt;0.001). With a median follow-up of 4.4 (95% CI 4.2 - 4.8) years, five-year OS was 57% (49-64) with PCTY and 49% (95% 46-53%) in ATG group, p=0.127. Five-year cumulative incidence of relapse was similar in both groups (22%, 95%CI 16-29 in PTCY vs 25%, 95%CI 22-28 in ATG; p=0.28). Notably, 5-year PFS was marginally higher for PTCY with 52% (95%CI 44-59) vs 44% (95%CI 40-48) for ATG, p=0.075, whereas 5-year NRM was 26% (95% CI 20-32%) vs 31% (95% CI 27-34) in PTCY and ATG, respectively, p=0.28. Grade II-IV acute GVHD incidence was lower using PTCY (22% [95% CI 17-28%] vs 30% [95% CI 26-33%]), p=0.035 while there was no difference for chronic GVHD (36% (29-43% with PTCY vs 38% (34-41%) in ATG at 5 years). Multivariable analyses confirmed a better OS and PFS for PTCY, with a HR of ATG of 1.34 (95% CI 1.02-1.76), p=0.04, and a better PFS for PTCY with a HR for ATG of 1.31 (95%CI 1.01-1.69) (Table 1). There was no apparent interaction between GvHD prophylaxis and IPSS-R or HLA matching, suggesting an effect exclusive to the type of GVHD prophylaxis used. Conclusion: This EBMT registry study suggests that MDS patients who received a transplant from an unrelated donor had a better OS and PFS using PTCY compared to ATG. This confirms that PTCY instead of ATG in this setting is a valid option.

Posttransplant cyclophosphamide versus antithymocyte globulin in patients with acute lymphoblastic leukemia treated with allogeneic hematopoietic cell transplantation from matched unrelated donors. A study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation.

The aim of this study was to compare two immunosuppressive strategies, based on the use of either rabbit antithymocyte globulin (ATG) or posttransplant cyclophosphamide (PTCY), as a prophylaxis of graft-versus-host disease (GVHD) for patients with acute lymphoblastic leukemia (ALL) in first complete remission who underwent hematopoietic cells transplantation from matched unrelated donors. Overall, 117 and 779 adult patients who received PTCY and ATG, respectively, between the years 2015 and 2020 were included in this retrospective study. The median patient age was 40 and 43years in the PTCY and ATG groups, respectively, and 37% and 35% of patients, respectively, had Philadelphia chromosome-positive ALL. In univariate analysis, the cumulative incidence of acute and chronic GVHD did not differ significantly between the study groups. The cumulative incidence of relapse at 2years was reduced in the PTCY group (18% vs. 25%; p=.046) without a significant impact on nonrelapse mortality (11% vs. 16% in the ATG group; p=.29). The rates of leukemia-free survival (LFS) and overall survival were 71% versus 59%, respectively (p=.01), and 82% versus 74%, respectively (p=.08). In multivariate analysis, the receipt of ATG compared with PTCY was associated with a reduced risk of extensive chronic GVHD (hazard ratio, 0.54; 95% confidence interval, 0.3-0.98; p=.04) and an increased risk of low LFS (hazard ratio, 1.57; 95% confidence interval, 1.01-2.45; p=.045). The receipt of ATG compared with PTCY, despite the reduced risk of extensive chronic GVHD, is associated with inferior LFS in adults with ALL who undergo hematopoietic cell transplantation from 10/10 human leukocyte antigen-matched unrelated donors. These findings warrant verification in prospective trials.