Matched Unrelated Donor Research Articles

Comparison of HLA-haploidentical donors with post-transplant cyclophosphamide versus HLA-matched unrelated donors in peripheral blood stem cell transplantation for acute myeloid leukaemia.

HLA-haploidentical haematopoietic cell transplantation with post-transplant cyclophosphamide (PTCy-haplo) is emerging as an effective alternative due to donor availability and safety. We conducted a nationwide retrospective study comparing the outcomes of PTCy-haplo with both anti-thymocyte globulin (ATG)-free and ATG-administered matched unrelated donors (MUD) transplantation, using peripheral blood stem cells as the first transplantation for acute myeloid leukaemia (AML). Our study showed a lower and slower haematopoietic recovery and a higher incidence of infection-related deaths after PTCy-haplo than after MUD transplantation. In addition, we revealed an increased risk of acute and chronic graft-versus-host disease (GVHD) in ATG-free MUD transplantation in comparison to PTCy-haplo. For grades III-IV acute GVHD, the hazard ratio (HR) was 2.71 (95% CI, 1.46-5.01), and for extensive chronic GVHD, the HR was 3.11 (95% CI, 2.07-4.68). There was no significant difference regarding overall survival amongst the groups. In addition, GVHD-free relapse-free survival (GRFS) was lower in ATG-free MUD transplantation than in PTCy-haplo (HR, 1.46; 95% CI, 1.17-1.82). Notably, ATG-administered MUD transplantation showed no significant difference in GRFS from PTCy-haplo, negating the advantage of PTCy. Our results suggest that PTCy-haplo could be viable for AML patients without an HLA-matched related donor.

Outcomes of haploidentical transplants with PT-CY vs 10/10 MUD transplants with ATG in Germany

AbstractAllogeneic stem cell transplantation (allo-HSCT) is the best curative treatment modality for many malignant hematologic disorders. In the absence of a matched related donor, matched unrelated donors (MUDs) and haploidentical donors (Haplo-Tx) are the most important sources of stem cells. However, multicenter real-life data that compare 10/10 MUD transplantations with Haplo-Tx are still limited. In this registry-based retrospective study, we compared the outcomes of allo-HSCTs from 10/10 MUDs with antithymocyte globulin (ATG)–based regimens (n = 7050) vs Haplo-Tx using posttransplant cyclophosphamide (PT-CY Haplo; n = 487) in adult patients with hematologic malignancies between 2010 and 2020. Cox proportional hazard models and competing risks regression models were formed to compare the outcomes of the groups. Overall survival (OS), Disease-free survival (DFS), and graft-versus-host disease (GVHD)–free and relapse-free survival (GRFS) were superior for 10/10 MUDs (OS [hazard ratio (HR), 1.27; confidence interval (CI), 1.10-1.47; P = .001]; DFS [HR, 1.17; CI, 1.02-1.34; P = .022]; GRFS [HR, 1.34; CI, 1.19-1.50; P < .001]). The risk of acute GVHD (aGVHD) grade 2 to 4, aGVHD grade 3 to 4, and chronic GVHD (cGVHD) was higher in the PT-CY Haplo group than the 10/10 MUD group (aGVHD grade 2-4 [HR, 1.46; CI, 1.25-1.71; P < .001]; aGVHD grade 3-4 [HR, 1.74; CI, 1.37- 2.20; P < .001]; cGVHD [HR, 1.30; CI, 1.11-1.51; P = .001]). A lower incidence of relapse was observed in the PT-CY Haplo group (relapse: HR, 0.83; CI, 0.69-0.99; P = .038). Unrelated 10/10 matched transplantation with ATG treatment leads to lower GVHD rates and improved survival rates compared with PT-CY Haplo transplantation in Germany.

Mucosal-associated invariant T cells are functionally impaired in pediatric and young adult patients following allogeneic hematopoietic stem cell transplantation and their recovery correlates with clinical outcomes.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells implicated in the response to fungal and bacterial infections. Their contribution to restoring T-cell immunity and influencing hematopoietic stem cell transplant (HSCT) outcomes remains poorly understood. We retrospectively studied MAIT-cell recovery in 145 consecutive children and young adults with hematologic malignancies undergoing allogeneic (allo)-HSCT between April 2019 and May 2022, from unrelated matched donor (MUD, N=52), with standard graft-versus-host-disease (GvHD) prophylaxis, or HLA-haploidentical (Haplo, N=93) donor after in vitro αβT/CD19-cell depletion, without post-HSCT pharmacological prophylaxis. With a median follow-up of 33 months (range, 12-49 months), overall survival (OS), disease-free survival (DFS), and non-relapse mortality (NRM) were 79.5%, 72%, and 7%, respectively; GvHD-free relapse-free survival (GRFS) was 63%, while cumulative incidence of relapse was 23%. While αβT cells were reconstituted 1-2 years post HSCT, MAIT cells showed delayed recovery and prolonged functional impairment, characterized by expression of activation (CD25, CD38), exhaustion (PD1, TIM3) and senescence (CD57) markers, and suboptimal ex vivo response. OS, DFS, and NRM were not affected by MAIT cells. Interestingly, higher MAIT cells at day +30 correlated with higher incidence of grade II-IV acute GvHD (19% vs. 7%, P=0.06). Furthermore, a greater MAIT-cell count tended to be associated with a higher incidence of chronic GvHD (cGvHD) (17% vs. 6%, P=0.07) resulting in lower GRFS (55% vs. 73%, P=0.05). Higher MAIT cells also correlated with greater cytomegalovirus (CMV) reactivation and lower late blood stream infections (BSI) (44% vs. 24%, P=0.02 and 9% vs. 18%, P=0.08, respectively). Future studies are needed to confirm the impact of early MAIT-cell recovery on cGvHD, CMV reactivation, and late BSI.

Access to Allogeneic Cell Transplantation Based on Donor Search Prognosis: An Interventional Trial.

Patients requiring allogeneic hematopoietic cell transplantation have variable likelihoods of identifying an 8/8 HLA-matched unrelated donor. A Search Prognosis calculator can estimate the likelihood. To determine if using a search algorithm based on donor search prognosis can result in similar incidence of transplant between patients Very Likely (>90%) vs Very Unlikely (<10%) to have a matched unrelated donor. This interventional trial utilized a Search Prognosis-based biologic assignment algorithm to guide donor selection. Trial enrollment from June 13, 2019-May 13, 2022; analysis of data as of September 7, 2023 with median follow-up post-evaluability of 14.5 months. National multi-center Blood and Marrow Transplantation Clinical Trials Network 1702 study of US participating transplant centers. Acute myeloid and lymphoid leukemias, myelodysplastic syndrome, Hodgkin's and non-Hodgkin's lymphomas, severe aplastic anemia, and sickle cell disease patients referred to participating transplant centers were invited to participate. 2225 patients were enrolled and 1751 were declared evaluable for this study. Patients were declared evaluable once it was determined no suitable HLA-matched related donor was available. Patients assigned to the Very Likely arm were to proceed with matched unrelated donor, while Very Unlikely were to utilize alternative donors. A third stratum, Less Likely (∼25%) to find a matched unrelated donor, were observed under standard center practices, but were not part of the primary objective. Cumulative incidence of transplantation by Search Prognosis arm. Evaluable patients included 1751 of which 413 (24%) were from racial/ethnic minorities. Search prognosis was 958 (55%) Very Likely, 517 (30%) Less Likely and 276 (16%) Very Unlikely. 1171 (67%) received HCT, 384 (22%) died without HCT, and 196 (11%) remained alive without HCT. Among the 1,234 patients, the adjusted cumulative incidence (95% CI) of HCT at 6-months was 59.8% (56.7-62.8) in the Very Likely group versus 52.3% (46.1-58.5) in the Very Unlikely (P=0.113). A prospective Search Prognosis-based algorithm can be effectively implemented in a national multicenter clinical trial. This approach resulted in rapid alternative donor identification and comparable rates of HCT in patients Very Likely and Very Unlikely to find a matched unrelated donor. Trial Registration: NCT#03904134.

Transplant Outcomes in Myelofibrosis: Impact of Donor Type (Cord Blood Grafts Supported by CD34+ selected Cells [Haplo-Cord] Versus Matched Donors)

BackgroundDespite the established potentially curative role of allogeneic hematopoietic cell transplantation (alloHCT) in managing MF, the choice of alternative donors for patients lacking matched donors remains a challenge, and the optimal graft source in this disease entity continues to be an ongoing debate. ObjectivesWe aimed to evaluate the impact of donor type: umbilical cord blood transplant supported CD34+ haploidentical donor (haplo-cord) vs adult matched related donor (MRD) and matched unrelated donor (MUD) in 40 adult patients with primary or secondary MF, including those progressing to accelerated phase (AP) or blast phase (BP), who underwent their first allo-HCT. The primary objective of this study was to analyze the impact of stem cell source on primary endpoints of overall survival (OS), graft versus host disease (GVHD) and non-relapse mortality (NRM). ResultsMedian follow-up for all alive patients was 53 months (range 0.3-63 months). Nine patients (22.5%) underwent an MRD allo-HCT, 15 patients (37.5%) underwent a MUD allo-HCT, and 16 patients (40%) underwent a haplo-cord allo-HCT. Four patients died without neutrophil engraftment: 3 (19%) in haplo-cord group and one (4%) in MRD/MUD group. The cumulative incidence of ANC engraftment by day 60 was 80% (95%CI 45-94) in the haplo-cord group and 92% (95%CI 65-98) in the MRD/MUD group (p=0.09). The cumulative incidence of platelet engraftment by day 60 was 59% (95%CI 27-81) in haplo-cord group and 75% (95%CI 51-88) in MRD/MUD group (p=0.4). OS was 62% at 1 year (95%CI 49-79) and 34% at 3 years (95%CI 21-55). The 3-yr OS was similar between the haplo-cord group and the MRD/MUD (37% vs 32%, p=0.9). The 1-yr OS for accelerated/blast phase AP/BP patients was 50% (95%CI 27-93) in the haplo-cord group, compared to 40% (95%CI 19-86) in the MRD/MUD. The 1-yr OS for chronic phase CP patients was 83% (95%CI 58-100) in the haplo-cord group, compared to 79% (95%CI 60-100) in the MRD/MUD group. The cumulative incidence of relapse at 3 years in the haplo-cord group was 13% (95%CI 1.8-34), and in the MRD/MUD group was 28% (95%CI 10-49) (p=0.36). 1-yr non-relapse mortality (NRM) was 38% (95%CI 15-61) in the haplo-cord group and 33% (95%CI 15-52) in the MRD/MUD group. 3-yr NRM was 48% (95%CI 19-72) in the haplo-cord group and 54% (95%CI 29-73) in MRD/MUD group(p=0.95). ConclusionWe showed no significant difference in OS, relapse, and NRM outcomes after haplo-cord transplant compared to adult matched donors’ grafts (MRD or MUD) in MF patients. However, there were more graft failures in patients transplanted with a haplo-cord transplants and delayed engraftments with inadequate haplo myeloid bridges. Despite the small sample size in our study, considering our findings and the availability of other alternative donors, using haplo-cord platforms may no longer be justified for myelofibrosis unless the UCB engraftment dynamics can be optimized.

Graft Versus Host Disease Prophylaxis in Matched Donor Stem Cell Transplantation: Post-transplantation Cyclophosphamide Combinations Versus Methotrexate/Tacrolimus

BackgroundThe use of post-transplant cyclophosphamide (PTCy) is highly effective in preventing graft versus host disease (GVHD) for haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT). There is limited data on the role of PTCy as GVHD prophylaxis in matched-sibling and fully matched-unrelated donor (MSD/MUD) allo-HSCT. MethodsOur single-center retrospective study aims to compare outcomes of PTCy alone or in combination with mycophenolate mofetil and tacrolimus (PTCy/MMF/TAC) relative to methotrexate and tacrolimus (MTX/TAC). The primary endpoint of our study was GVHD-free, relapse free survival (GRFS). Secondary endpoints were overall survival (OS), disease free survival (DFS), and incidence of severe acute and chronic GVHD. We identified 74 adult patients who underwent MSD/MUD allo-HSCT at our institution from 2015 to 2023. ResultsWithin our cohort, 33.8% (n = 25) received MTX/TAC, while 54.0% (n = 40) received PTCy/MMF/TAC, and 12.2% (n = 9) received PTCy alone. Patients receiving PTCY had the longest time to neutrophil engraftment relative to MTX/TAC (15 days vs. 12 days, P = .010). PTCy/MMF/TAC was associated with improved GRFS relative to MTX/TAC (hazard ratio [HR] = HR 0.42, 95% CI 0.19-0.93, P = .031), which persisted when controlling for age. Incidence of chronic GVHD was lower in the PTCy/MMF/TAC group compared to MTX/TAC (1-year 9.0% vs. 30.1%, HR 0.19, 95% CI 0.06-0.59, P = .005). However, OS and DFS were comparable across all groups. ConclusionsOur results demonstrate decreased rates of severe chronic GVHD resulting in improved GRFS when using PTCy/TAC/MTX as GVHD prophylaxis compared to MTX/TAC in MSD/MUD.

Older MRD vs. younger MUD in patients older than 50 years with AML in remission using post-transplant cyclophosphamide.

An increasing number of older patients with acute myeloid leukemia (AML) are offered an allogeneic hematopoietic stem cell transplantation (allo-HSCT). Normally, older patients have older matched related donors (MRD). Matched unrelated donors (MUD) are an important alternative, but it remains unclear whether a younger MUD is associated with better outcomes, especially in the context of post-transplant cyclophosphamide (PTCy). We compared outcomes of patients older than 50 years with AML in first complete remission (CR1) and receiving a first HSCT from a 10/10 MUD aged younger than 40 years to those receiving a graft from a MRD aged older than 50 years, using PTCy and with well-known transplant conditioning intensity (TCI) score. A total of 345 consecutive patients were included and classified according to TCI score as low, intermediate, or high. On multivariable analysis in the TCI-intermediate/high group, MUD was associated with better graft-versus-host disease-free, relapse-free survival, lower non-relapse mortality and lower relapse incidence. For patients receiving a TCI-low regimen, outcomes are independent on the type of donor. In patients with AML in CR1, older than 50 years and receiving a TCI-intermediate/high conditioning regimen using PTCy, a MUD younger than 40 years is preferable over a MRD older than 50 years.

Comparison of Cyclophosphamide-Based Graft Versus Host Disease Prophylaxis after "Allogeneic Stem Cell Transplantation from 9/10 HLA Matched Unrelated Donor'' with Standard Graft Versus Host Disease Prophylaxis after "10/10 HLA Matched Relative Donor'' Transplant.

Background: Graft Versus Host Disease (GvHD), which can be observed at a rate of 30-80% after allogeneicstem cell transplantation (ASCT) is an important complication that adversely affects the survival and quality of the life of patients.Posttransplant cyclophosphamide (PTCy) effectively prevents GvHD after HLA-haploidentical ASCT. In our study, the use of PTCy in 1-antigen HLA-mismatched unrelated donor (9/10MMUD) ASCT was compared with standard GvHD prophylaxis in HLA-identical related donor (MRD) ASCT. Materials and Methods: We conducted a retrospective study of the comparison of 42 patients with 9/10 MMUD ASCT receiving PTCy+Methotrexate (MTX)+Calcineurin Inhibitor (CNI) and 37 patients with HLA-identical MRD who received MTX+CNI in 3 bone marrow transplantation centers. Results: Cumulative incidences of grade I-II (64.6% vs 45.4%, p=0.187) or grade III to IV acute GvHD (35.4% vs54.6%,p=0.187)and chronic GvHD (11.9% vs 29.7%, p=0.096) were similar in the PTCy group and control group. No statistically significant differences were observed between PTCy and the control group in overall survival rate (52.4% vs 62.2%, p=0.381), progression-free survival (1483.97 vs 1200.70 days, p=0.502), relapsed-related mortality rate (21.4% vs 16.2%, p=0.556) and treatment-related mortality rate (16.7% vs 21.6%, p=0.575). Conclusion: With the addition of PTCy to standard GvHD prophylaxis in 9/10MMUD ASCT, the risk of GvHD due to incompatibility and unrelated transplantation is eliminated, and transplantation success is achieved with MRD ASCT. PTCy-based prophylaxis is an effective and safe strategy to prevent GvHD in 9/10 MMUD ASCT without increasing the risk of relapse and treatment-related mortality.

Permissible HLA mismatches in 9/10 unrelated donor pediatric stem cell transplants using HLA-EMMA: an EBMT Inborn Errors Working Party study

AbstractAllogeneic hematopoietic stem cell transplantation (HSCT) with mismatched unrelated donors (MMUD) is associated with inferior outcome compared with matched unrelated donors (MUDs). We aimed to identify permissible mismatches using HLA epitope mismatch algorithm, which determines permissibility by analyzing amino acid sequences, in a single-center cohort of 70 pediatric 9/10 MMUD HSCTs and 157 10/10 MUDs for comparison. Amino acid matching was evaluated for the whole HLA protein, the α-helices, and the β-sheets, in both host vs graft (HvG) and graft vs host (GvH) direction. Superior event-free survival (EFS) was found in 13 patients permissibly mismatched in the HvG direction (totalHvG, 92% vs 58% at 1 year; P = .009) and in 21 patients matched on the α-helices (αHvG, 90% vs 53%; P = .002). These rates were similar to EFS rates in patients with 10/10 MUDs (90% vs 80%; P = .60). EFS was not related to β-sheet amino acid matching, nor to matching in the GvH direction. Overall survival (OS) rates trended similarly to those of EFS for amino acid mismatches (totalHvG, 92% vs 74%; P = .075; αHvG, 90% vs 71%; P = .072). These findings were reproduced in an EBMT Registry inborn errors cohort of 271 pediatric 9/10 MMUD HSCTs and 929 10/10 MUD HSCTs, showing a significant effect of αHvG matching on both OS and EFS and similar OS and EFS between αHvG matched MMUDs and 10/10 MUDs. In summary, HvG amino acid matching on the α-helices identifies 9/10 MMUDs with permissible mismatches, which are correlated with favorable transplant outcomes similar to those of matched donors.

Childhood myelodysplastic syndromes: Is cytoreductive therapy useful before allogeneic hematopoietic stem cell transplantation?

For most patients with childhood myelodysplastic syndrome (cMDS), allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative option. In the case of increased blasts (cMDS-IB), the benefit of pretransplant cytoreductive therapy remains controversial. In this multicenter retrospective study, the outcomes of all French children who underwent allo-HSCT for cMDS reported in the SFGM-TC registrybetween 2000 and 2020 were analyzed (n = 84). The median age at transplantation was 10.2 years. HSCT was performed from matched sibling donors (MSD) in 29% of the cases, matched unrelated donors (MUD) in 44%, haploidentical in 6%, and cord blood in 21%. Myeloablative conditioning was used in 91% of cases. Forty-eight percent of patients presented with cMDS-IB at diagnosis (median BM blasts: 8%). Among them, 50% received pretransplant cytoreductive therapy. Five-year overall survival (OS), cumulative incidence of nonrelapse mortality (NRM), and relapse were 67%, 26%, and 12%, respectively. Six-month cumulative incidence of grade II-IV acute graft-versus-host disease was 46%. Considering the whole cohort, age under 12, busulfan/cyclophosphamide/melphalan conditioning or MUD were associated with poorer 5-year OS. In the cMDS-IB subgroup, pretransplant cytoreductive therapy was associated with a better OS in univariate analysis. This seems to be mainly due to a decreased NRMsince no impact on the incidence of relapse was observed. Overall, those data may argue in favor of cytoreduction for cMDS-IB. They need to be confirmed on a larger scale and prospectively.

Donor types and outcomes of transplantation in myelofibrosis: a CIBMTR study

AbstractWe evaluate the impact of donor types on outcomes of hematopoietic cell transplantation (HCT) in myelofibrosis, using the Center for International Blood and Marrow Transplant Research registry data for HCTs done between 2013 and 2019. In all 1597 patients, the use of haploidentical donors increased from 3% in 2013 to 19% in 2019. In study-eligible 1032 patients who received peripheral blood grafts for chronic-phase myelofibrosis, 38% of recipients of haploidentical HCT were non-White/Caucasian. Matched sibling donor (MSD)–HCTs were associated with superior overall survival (OS) in the first 3 months (haploidentical hazard ratio [HR], 5.80 [95% confidence interval (CI), 2.52-13.35]; matched unrelated (MUD) HR, 4.50 [95% CI, 2.24-9.03]; mismatched unrelated HR, 5.13 [95% CI, 1.44-18.31]; P < .001). This difference in OS aligns with lower graft failure with MSD (haploidentical HR, 6.11 [95% CI, 2.98-12.54]; matched unrelated HR, 2.33 [95% CI, 1.20-4.51]; mismatched unrelated HR, 1.82 [95% CI, 0.58-5.72]). There was no significant difference in OS among haploidentical, MUD, and mismatched unrelated donor HCTs in the first 3 months. Donor type was not associated with differences in OS beyond 3 months after HCT, relapse, disease-free survival, or OS among patients who underwent HCT within 24 months of diagnosis. Patients who experienced graft failure had more advanced disease and commonly used nonmyeloablative conditioning. Although MSD-HCTs were superior, there is no significant difference in HCT outcomes from haploidentical and MUDs. These results establish haploidentical HCT with posttransplantation cyclophosphamide as a viable option in myelofibrosis, especially for ethnic minorities underrepresented in the donor registries.

Treatment of acute myeloid leukemia with Orca-T.

6552 Background: Allogeneic hematopoietic stem cell transplants (alloHSCT) offer a potential curative treatment for many hematological cancers, however, traditional alloHSCT is associated with high mortality from complications including infection, graft versus host disease (GvHD) and relapse. Orca-T is an investigational allogeneic T-cell immunotherapy that includes stem and immune cells, derived from allogeneic donors, that leverages highly purified, polyclonal donor regulatory T cells to control alloreactive immune responses. In this sub-group analysis, we evaluated the safety and efficacy of patients with acute myeloid leukemia who were treated with Orca-T. Methods: Data from 37 patients with the diagnosis of acute myeloid leukemia (AML) in CR/CRi who received myeloablative conditioning with busulfan, fludarabine, and thiotepa (BFT) followed by Orca-T by 6/30/22 as part of a multicenter phase 1b single-arm trial (NCT04013685) are reported here. Patients enrolled in the phase 1b trial who did not meet these criteria were not included in this analysis. Patients received BFT prior to Orca-T, followed by single-agent GvHD prophylaxis with tacrolimus, and had an 8/8 related or unrelated matched donor. Donors were matched via DNA-based high-resolution typing of HLA-A, -B, -C, and -DRB1. Results: Orca-T was successfully manufactured at a centralized GMP facility, distributed, and infused at study sites throughout the U.S. Vein-to-vein time (i.e. time between end of donor apheresis to start of recipient’s Orca-T infusion) was &lt; 72 hours for all patients, with the majority &lt; 60 hours. Median age was 51 years, 49% were female and 16% were of Hispanic or Latino ethnicity. Twenty-three (62%) had matched related donors and 14 (38%) had matched unrelated donors. Baseline HCT-CI score was 3 and 4 in 27% and 8% of the patients, respectively. The majority had intermediate DRI scores (89%) and 41% were MRD positive at baseline. The median duration of follow-up was 14 months. Relapse-free survival at 12 months was 81.4% (95% CI: 62.9, 91.2). Non-relapse mortality and overall survival were 0% and 100% at 12 months, respectively. Conclusions: These encouraging results suggest that investigational Orca-T could represent a reduced toxicity alternative to conventional alloHSCT. This combination of Orca-T with myeloablative BFT led to &gt; 80% RFS without treatment related mortality, and 100% overall survival in this AML patient population. These outcomes were accomplished with consistent and reliable cell manufacturing and distribution of Orca-T at a national scale. A multi-center randomized controlled phase 3 trial comparing Orca-T to SOC, utilizing BFT or TBI-based conditioning, will complete enrollment during the first half of 2024. (NCT05316701). Clinical trial information: NCT04013685 .

Hematologic malignancies in Li-Fraumeni syndrome.

10613 Background: Li-Fraumeni Syndrome (LFS) is a hereditary cancer predisposition syndrome caused by mutations in the tumor suppressor gene TP53. Since its discovery, a growing list of cancers have been described in association with LFS, predominantly solid tumors. However, hematologic malignancies (HMs) cumulatively account for 4-10% of cancer diagnoses in LFS. In this study, we present the largest series of HMs in families with LFS with detailed clinical courses. Methods: This was a two-center retrospective observational cohort study conducted at the University of Utah and the University of Wisconsin-Madison with IRB approval. Cancer genetics clinic registries were reviewed to identify all families with LFS who also had a confirmed diagnosis of a HM. To meet criteria for LFS, the patient had to have a confirmed germline pathologic or likely pathologic TP53 variant. Patients with a TP53 variant of unknown significance (VUS) were also included if they met classical LFS testing criteria. Data was gathered by manual chart review of both the families’ histories and electronic health records. Results: Among the 121 families identified with LFS, 35 (29%) families had one or more HM. Of these, 17 individuals from 16 families (13%) had confirmed germline TP53 mutations. The most frequent HMs found were acute lymphoblastic leukemia (ALL) (n=6), non-Hodgkin lymphoma (NHL) (n=5), myelodysplastic syndromes (MDS) (n=3), and chronic lymphocytic leukemia (CLL) (n=2). Acute myeloid leukemia (AML), Langerhans cell histiocytosis (LCH), and chronic myeloid leukemia (CML) were each diagnosed once. Most cases were identified in adulthood (n=12, 71%). Of the 19 total HMs, the minority (n=5, 26%) were diagnosed post-cytotoxic therapy and only six (35%) individuals had received a diagnosis of LFS prior to HM diagnosis. The MDS/AML cohort (n=4) all exhibited bi-allelic inactivation of TP53. Two of these four patients achieved long term survival after matched-unrelated donor (MUD) hematopoietic stem cell transplant (HSCT). All three patients who underwent MUD donor HSCT had immune-mediated adverse events. Conclusions: In this study we found a significantly higher incidence of HMs in LFS than previously described, with a predominance of lymphoid over myeloid malignancies. The majority of patients had excellent outcomes after standard of care therapy pointing towards more favorable outcomes for patients with LFS and HMs than previously reported. We also report several unusual immune-mediated adverse events in our patients indicating possible immunogenicity of some TP53 variants. Most patients did not have prior exposure to cytotoxic treatments and were diagnosed with the HM prior to their LFS diagnosis. We also show that 38% of individuals with an HM have multiple family members with an HM, consistent with a familial HM pattern. This underscores the importance of detailed family and personal histories in HM patients found to carry a somatic TP53 variant.

Safety outcomes in adult patients with AML who achieved their first complete remission with GO prior to HSCT.

e18504 Background: Gemtuzumab ozogamicin (GO) is approved in the US for the treatment of newly diagnosed and relapsed/refractory (R/R) CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients of 1 month and older and 2 years and older, respectively. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative therapy for most adult patients with AML in first complete remission (CR1). Clinical studies have linked GO with hepatotoxicity and hepatic veno-occlusive disease (VOD); the risk of these events may be further elevated in patients receiving HSCT. This study aimed to characterize the toxicity after HSCT in adult patients with AML who were treated with GO prior to HSCT. These analyses look at outcomes in patients who were in CR1 at the time of HSCT. Methods: This non-interventional post-authorization safety study used de-identified healthcare data from the Center for International Blood and Marrow Transplant Research (CIBMTR) database. Data were collected from adult patients in the US with newly diagnosed AML treated with GO prior to proceeding with HSCT. Data collection began on 01 September 2017, data cutoff was 04 July 2023. Results: We present data of 84 patients receiving HSCT for AML in CR1 from 19 centers with a median follow-up of 23.9 months (range, 3.0-49.7). Median age was 54.2 y (range, 18.7-74.5); 55% male. Total cumulative GO dose was 1-3 mg/m2 in 15 (18%), 4-6 mg/m2 in 15 (18%), 7-9 mg/m2 in 28 (33%) and ≥10 mg/m2 in 8 (12%) patients. Measurable residual disease (MRD) was undetectable in 50% (n=42) of patients after GO and 51% (n=43) of patients at the time of HSCT. Most patients (58%; n=49) received myeloablative conditioning and 57% (n=48) received HLA matched unrelated donor HSCT. Non-fatal VOD was reported in 6 (7%) patients, most cases were mild (n=5; 83%). Cumulative incidences of transplant-related mortality (TRM) were: 6 months, 7% (95% CI, 3-14); 2 years, 15% (95% CI, 7-25). The 2-year relapse rate was 26% (95% CI, 16-36%). Kaplan-Meier probabilities of leukemia-free survival (LFS) outcomes at 1 and 2 years were, 68% (95% CI, 57-78) and 59% (95% CI, 47-71), respectively. There were 22 deaths during the study, 10 (46%) from relapse of AML, no VOD-related deaths were observed. Conclusions: The use of GO prior to allogeneic HSCT appears to be safe with low rates of posttransplant VOD observed in patients with AML in CR1. TRM and survival outcomes are similar to historically reported rates. Clinical trial information: B1767034.

Anti-T-lymphocyte globulin improves GvHD-free and relapse-free survival in myelofibrosis after matched related or unrelated donor transplantation

Acute and chronic graft-versus-host disease (GvHD) are major complications of allogeneic hematopoietic cell transplantation (alloHCT). In vivo T-cell depletion with anti-T-lymphocyte globulin (ATLG) as part of the conditioning regimen prior to alloHCT is frequently used as GvHD prophylaxis, but data on its role in myelofibrosis is scarce. We took advantage of an international collaborative network to investigate the impact of ATLG in myelofibrosis undergoing first alloHCT. We included 707 patients (n = 469 ATLG and n = 238 non-ATLG prophylaxis). The cumulative incidence of acute GvHD grade II-IV was 30% for the ATLG group vs. 56% for the non-ATLG group (P < 0.001). Acute GvHD grade III-IV occurred in 20% vs. 25%, respectively (P = 0.01). Incidence of mild-to-severe chronic GvHD was 49% vs. 50% (P = 0.52), while ATLG showed significantly lower rates of severe chronic GvHD (7% vs. 18%; P = 0.04). GvHD-free and relapse-free survival (GRFS) at 6 years was 45% for the ATLG group vs. 37% for the non-ATLG group (P = 0.02), driven by significantly improved GRFS of ATLG in matched related and matched unrelated donors. No significant differences in risk for relapse, non-relapse mortality, and overall survival were observed. Multivariable modeling for GRFS showed a 48% reduced risk of GvHD, relapse, or death when using ATLG.

The role of donor type and pre-transplant immunosuppression on outcomes of hematopoietic stem cell transplantation in children and young adults with severe aplastic anemia.

The goal of this study was to assess the effect of donor type and pre-transplant immunotherapy (IST) on outcomes of hematopoietic stem cell transplantation (HSCT) for children and young adults with severe aplastic anemia (SAA). This retrospective, multi-center study included 52 SAA patients, treated in 5 pediatric transplant programs in Florida, who received HSCT between 2010 and 2020 as the first- or second-line treatment. The median age at HSCT for all 52 patients was 15 years (range 1-25). The 3-year overall survival (OS) by donor type were as follows: 95% [95% CI 85.4-99] for matched related donors (MRD) (N = 24), 84% [95% CI 63.5-99] for haploidentical (N = 13), and 71% [95% CI 36-99] for matched unrelated donors (MUD) (N = 7). The 3-year OS was 81% [95% CI 69.7-99] for all patients, 90.5% [95% CI 79.5-99] for non-IST patients (N = 27), and 70% [95% CI 51-99] for IST patients (N = 24) (log-rank p = .04). Survival of haploidentical HSCT (haplo-HSCT) recipients with post-transplant cyclophosphamide (PTCy) (N = 13) was excellent for both groups: 100% for non-IST patients (N = 3) and 80% for IST patients (N = 10). The 3-year OS for patients with previous IST by donor type in groups where >5 patients were available was 78.8% [95% CI 52.3-99] for haplo-HSCT (N = 10) and 66.7% [95% CI 28.7-99] for MUD (N = 6). Although it appears that patients receiving HSCT ≥6 months after the start of IST had worse survival, the number of patients in each category was small and log-rank was not significant(p = .65). Patients receiving MUD and haplo-HSCT with PTCy had similar outcomes, suggesting that haplo-HSCT with PTCy could be included in randomized trials of upfront IST versus alternative donor HSCT.

Retrospective study to compare the outcomes of matched related donor vs matched unrelated donor in patient with acute myeloid leukaemia

BackgroundIndia's need for bone marrow donation and transplantation is increasing in the context of the rising incidence of haematological neoplasms like acute myeloid leukaemia (AML). The use of matched related donors (MRD) for hematopoietic stem cell transplantation (HSCT) is a feasible option, but the lack of HLA-matched donors in India remains a significant obstacle to successful treatment. MethodologyThis retrospective study was conducted at the Department of Hemato-Oncology & Bone Marrow Transplant, Rajiv Gandhi Cancer Institute in New Delhi, India over a period of 6 months. The study enrolled 77 AML MRD and 19 AML MUD patients based on the inclusion and exclusion criteria. ResultThe one-year survival rate was higher in MRD than in MUD, but there was no significant difference in mortality in multivariate analysis. The study also found that chronic graft-versus-host disease (GVHD) and relapse were associated with worse survival outcomes in both MRD and MUD HSCT. ConclusionThis study supports the use of matched unrelated donor (MUD) transplant for HSCT in AML patients when a matched sibling donor is not available.

MODELS OF HLA-DPB1 PERMISSIVENESS AND UNRELATED DONOR HEMATOPOIETIC CELL TRANSPLANTATION

In current allo-HCT practice, a fully HLA-matched sibling donor is the best donor associated with improved transplant outcomes. When a matched sibling donor is unavailable, the second best available donor option is a matched unrelated donor (MUD), either HLA 8/8 or HLA 10/10. One notable characteristic in the MUD setting is that HLA-DPB1 mismatches are present in around 80/85% of unrelated donor/recipient pairs. This unique feature has an additional layer of complexity as these HLA-DPB1 incompatibilities may be further divided into permissive and non-permissive mismatches by two biological-driven permissiveness models, namely T-cell epitope (TCE) and DP expression. In the current review article, we described the basics of T-cell allorecognition, the unique HLA-DPB1 immunogenetics, the early conflicting results regarding HLA-DPB1 mismatching in allo-HCT, the development and the clinical impact of T-cell epitope and Expression models, the new indirect allorecognition algorithm of HLA-DPB1 permissiveness (PIRCHE model), the role of HLA-DPB1 in nonmalignant disease setting, and future perspectives on HLA-DPB1 permissiveness. Keywords: HLA-DPB1, Permissive mismatch, Unrelated donor

Comparison of Older Related versus Younger Unrelated Donors for Older Recipients of Allogeneic Hematopoietic Cell Transplantation with Acute Myeloid Leukemia or Myelodysplastic Syndrome: A Large Single-Center Analysis

For patients undergoing allogeneic hematopoietic cell transplantation (alloHCT), HLA-matched related donors (MRDs) have traditionally been the preferred donor source. However, as the age of recipients increases, their sibling donors are aging as well. In this study, we investigated whether younger matched unrelated donors (MUDs) might be a better donor source than similarly aged sibling donors for patients age >60 years with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). A total of 499 patients age 60 to 70 years with AML or MDS who underwent alloHCT from an older MRD (donor age ≥50 years) or a younger MUD (donor age ≤35 years) between 2010 and 2022 were evaluated. Of these, 360 patients (72%) received an MUD graft and 139 (28%) received an MRD graft. The median recipient age was 64 years in the MRD group and 66 years in the MUD group. With a median follow-up among survivors of 53 months (range, 9 to 147 months ), the 4-year progression-free survival was 40% in the MRD group and 41% in the MUD group (P = .79) and the 4-year overall survival was 50% and 44%, respectively (P = .15), with no between-group differences in nonrelapse mortality, relapse, and acute or chronic graft-versus-host disease. In the MUD group, we also compared the effect of donor age 18 to 24 years and donor age 25 to 35 years and found no differences in outcomes between the groups. We conclude that outcomes are comparable between the use of older MRDs and use of younger MUDs for elderly patients with AML or MDS, that there is no donor age effect among younger MUDs, and that the use of either donor type is reasonable.

Analysis of efficacy and prognosis of allogeneic hematopoietic stem cell transplantation for the treatment of combined immunodeficiency

Objective: To evaluate the efficacy of allogeneic hematopoietic stem cell transplantation for the treatment of combined immunodeficiency (CID) and explore prognostic risk factors. Methods: In this retrospective cohort study, clinical characteristics, laboratory tests and prognosis of 73 CID children who underwent allogeneic hematopoietic stem cell transplantation from February 2014 to April 2022 in the Children's Hospital of Fudan University were analyzed. Based on the subtypes of diseases, all patients were divided into severe combined immunodeficiency disease (SCID) group and other CID group. Based on the types of donors, all patients were divided into matched sibling donor group, matched unrelated donor group, unrelated cord blood group, and haploidentical donor group. Kaplan-Meier method and Log-Rank test were used to analyze the survival data. Cox regression was used to analyze prognostic factors. Results: Among the 73 patients, there were 61 (84%) males and 12 (16%) females. Fifty-five (75%) patients were SCID, and 18 (25%) patients were other CID. Donor source included 2 (3%) matched sibling donors (MSD), 3 (4%) matched unrelated donors (MUD), 64 (88%) unrelated cord blood (UCB), and 4 (5%) haploidentical donors. The age at transplant was 10.7 (5.9, 27.5) months, and the follow-up time was 36.2 (2.5, 62.9) months. The 3-year overall survival rate of 73 patients with CID was (67±6) %. No significant difference was found in the 3-year overall survival rates between patients with SCID (55 cases) and other CID (18 cases) ((64±7) % vs. (78±10) %, χ2=1.31, P=0.252). And no significant difference was found in the 3-year overall survival rates among patients who received MSD or MUD (5 cases), UCB (64 cases), and haploidentical donor (4 cases) transplant (100% vs. (66±6)% vs. (50±25) %, χ2=2.30, P=0.317). Cox regression analysis showed that the medical history of sepsis (HR=2.55, 95%CI 1.05-6.20, P=0.039) and hypoalbuminemia at transplant (HR=2.96, 95%CI 1.14-7.68, P=0.026) were independent risk factors for the prognosis of allogeneic hematopoietic stem cell transplantation in pediatric patients with CID. Conclusions: Allogeneic hematopoietic stem cell transplantation is an effective treatment for CID. The medical history of sepsis and hypoalbuminemia at transplant were risk factors for prognosis. Enhancing infection prevention and nutritional intervention before transplant can improve patient prognosis.