Stem Cell Donor Research Articles

Umbilical Cord Blood Stem Cells As Third-Party Adjuvant Infusion in Human Leukocyte Antigen Antibody-Positive Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: The presence of human leukocyte antigen (HLA) antibodies, even if not donor-specific antibodies (DSA), is an important risk factor for graft failure (GF) or poor graft function (PGF) in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, there is no ideal strategy for eradicating or descending HLA antibodies in this population. In the present study, we investigated the efficacy and safety of unrelated umbilical cord blood stem cells (CBCs) as a third-party adjuvant infusion in patients with HLA antibodies undergoing allo-HSCT. Methods:Patients undergoing allo-HSCT from July 2017 to June 2021 were enrolled in this study and HLA antibodies were routinely tested before transplantation. Patients were divided into three groups: Group A (patients with positive/weak positive HLA antibodies and with CBCs infusion), Group B (patients with HLA antibodies positive/weak positive without CBCs infusion), and Group C (patients without HLA antibody nor CBCs infusion). Single unrelated CBCs (HLA4/6 or more compatible ) were infused four hours before donor stem cells. The clinical characteristics of the patients and the paired donors were collected. The occurrence of granulocyte and platelet engraftment time, graft-versus-host disease (GVHD), cytomegalovirus (CMV), Epstein-Barr virus (EBV) reactivation, one-year and two-year relapse-free survival (RFS), transplantation-related mortality (TRM), and overall survival (OS) for all three groups of patients were also analyzed in this study. Results:A total of 90 patients were included in this study (17 in group A, 36 in group B, and 37 in group C). The baseline clinical characteristics of the patients were presented in Table 1. No obvious adverse effects were observed in the process of CBCs infusion. All the patients achieved 100% donor chimerism without CBCs engraftment. There were no significant differences in granulocyte and platelet engraftment time between the three groups. Two patients in Group A and C, and 3 patients in Group B developed PGF, respectively. There were no significant differences in the incidence and grades of acute or chronic GVHD among the three groups ( Figure A, B). In the first 3 months after allo-HSCT, the incidence of EBV reactivation was higher in patients in Group B than that in Group A and C, respectively ( Figure C). There were no significant differences in the CMV reactivation between the three groups in the first 3 months after transplantation ( Figure D). Patients in Group A and B both had lower 1-year RFS and higher 1-year TRM, compared with Group C, respectively ( Figure E, F). However, there were no significant statistical differences in 2-year RFS and TRM between the three groups. Although patients in Group A had longer 2-year OS than that in Group B, there were no significant differences between the two groups: Group A vs Group B (76.5% vs 55.6%, P = 0.194), Group B vs Group C (55.6% vs 85.5%, P < 0.05)( Figure G). A multifactorial Cox regression risk model was established to explore the risk factors affecting OS and suggested that patients' pre-transplantation status (with active malignant disease or minimal residual disease positive) and HLA antibodies pre-transplant were the most independent risk factors for OS (HR = 4.380, 95% CI = 1.544-12.427, P<0.05; HR = 0.196, 95% CI = 0.065-0.587, P<0.05). Conclusions: Patients with positive/weak positive HLA antibodies receiving CBCs as a third-party adjunctive infusion were safe, and there was a benefit in the incidence of EBV reactivation compared to such a population without CBCs infusion. The patients with negative HLA antibodies had higher 1-year RFS and lower 1-year TRM than those with positive/weakly positive HLA antibodies regardless CBCs infusion. Due to the small number of included cases, we will expand the sample number to further validate our results in the future.

Comparison of Biosimilar Filgrastim (Nivestym) Versus Originator Filgrastim (Neupogen) for Peripheral Blood Stem Cell Mobilization for Allogeneic Hematopoietic Stem Cell Transplantation

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is an optimal and potentially curative therapy for patients with hematologic malignancies. Granulocyte colony-stimulating factor (G-CSF) is used for the mobilization of peripheral blood stem cells (PBSCs) in allogeneic donors, and an optimal CD34 cell dose plays a critical role in successful transplantation. Nivestym, a biosimilar G-CSF to the originator Filgrastim (Neupogen), is now used by multiple institutions as it has become more available; however, there is a lack of data in this regard among healthy donors for allogeneic HSCT mobilization. In this study, we aim to compare the efficacy of Nivestym compared to Neupogen for allogeneic donor PBSC mobilization. Methods: For this retrospective single-center study, we included all (n=541) adult allogeneic HSCT donors at the University of Kansas Medical Center receiving Nivestym (January 2013-July 2020) or Neupogen (July 2020-June 2023) for donor PBSC mobilization. We conducted a bivariate analysis utilizing the ANOVA test. Statistical analyses were performed using SPSS version 28. Statistical significance was determined at p<0.05. Results: Our study included 541 allogeneic HSCT donors who received Neupogen (n=345, 64%) or Nivestym (n=196, 36%) for PBSC mobilization. The median age was 47 (range 17-76) years. The median donor weight was 86 (95% CI 87-91) kilograms. Donors receiving Neupogen had similar pre-GCSF WBC count (median 45 vs 47 K/uL, p=0.739), pre-GCSF CD34 percentages (median 17% vs 17%, p=0.527), and pre-GCSF circulating CD34 count (median 74 vs 74 million cells/kg, p=0.842) compared to donors receiving Nivestym. Neupogen recipients had similar median PBSC product total neutrophil count (TNC, 6.8 vs 6.5 K/uL, p=0.347), product CD34 percentage (75% vs 79%, p=0.068), absolute CD34 count (503 vs 533 million cells, p=0.636), and final CD34 dose (6.1 vs 6.3 million cells/kg, p=0.365) compared to Nivestym recipients. Seven percent (n=28) of donors needed two days of PBSC collection to achieve the target PBSC dose, with a statistically similar proportion noted in Neupogen (n=25, 7.3%) and Nivestym (n=13, 6.6%) cohorts. In a subgroup analysis stratified by age, donors aged 35 or older (n=154) had similar responses in all mentioned variables (p>0.05); however, for donors under the age of 35 years, the CD34 dose was higher in donors receiving Neupogen compared to Nivestym (median 6.9 vs 6.3 million cells/kg, p=0.044). Most of the PBSC collections (98%) were completed in one day, except for five donors in both Neupogen (5%) and Nivestym (8.5%) cohorts. Conclusions: Biosimilar G-CSF (Nivestym) demonstrated similar efficacy for peripheral blood stem cell mobilization compared to the originator G-CSF (Neupogen) among allogeneic HSCT donors. In donors aged 35 years or younger, a slightly lower PBSC product CD34 count was noted with Nivestym compared to Neupogen.

Score to Guide Donor Choice in Haploidentical Stem Cell Transplant Using Post-Transplant Cyclophosphamide for Patients with Acute Myeloid Leukemia: A Study from the Acute Leukemia Working Party of the EBMT

Introduction: There is paucity of information to guide selection of the most appropriate stem cell donor for haploidentical (Haplo) hematopoietic stem cell transplant (HSCT). Patients and Methods: We retrospectively analyzed the characteristics of haploidentical family donors that may affect transplant outcomes in patients with acute myeloid leukemia (AML) who received graft-versus-host disease (GVHD) prophylaxis with postransplant cyclophosphamide (PTCy) registered in the EBMT database. The primary endpoint was GVHD and relapse-free survival (GRFS). Results: Overall, 2200 patients were included with a median age of 56 years (range, 18-75); 1742 (79%) were in complete remission and 1246 (56.6) received reduced intensity conditioning. Regarding donors, the median age was 37 years (range, 8-71), 820 (37%) were females of which 458 (21%) were used for male recipients, 1252 (57%) had positive CMV serostatus, 1631 (74%) donated peripheral blood (PB) and 1638 (75%) had ≥ 4/8 HLA mismatch with the recipient. 100-day acute GVHD grade II-IV and III-IV and 2-year chronic and chronic extensive GVHD were 28% (95% CI 26-30), 11% (95% CI 10-12), 33% (95% CI 31-35) and 14% (95% CI 12-15), respectively. After median follow-up of 24 months, the cumulative incidence of relapse and non-relapse mortality (NRM) and the probability of leukemia-free survival (LFS), overall survival (OS) and GRFS were 26% (95% CI 24-28), 22% (95% CI 20-24), 52% (95% CI 50-55), 57% (95% CI 55-60) and 41% (95% CI 39-43), respectively. In multivariable analysis, donor-related risk factors with a negative impact on GRFS were older age (HR 1.1; 95% CI 1.04-1.15), use of PB (HR 1.19; 95% CI 1.04-1.37), and female donors to male recipients (HR 1.25; 95% CI 1.09-1.43). We further developed a score that distinguished 4 groups with 0 (241), 1 (913), 2 (863) or 3 (183) donor-related risk factors. GRFS was 57% (95% CI 50-63), 43% (95% CI 39-46), 37% (95% CI 33-40), and 30% (95% CI 23-38), respectively (P < 0.001) (Figure 1). The score was also able to stratify risk groups for acute and chronic GVHD, NRM, LFS and OS. Conclusion: Donor variables have an important impact on AML patient's outcome after Haplo-HSCT using PTCy. With three simple donor characteristics, age, gender and stem cell source, we were able to generate a score that may help to select the most appropriate donor in clinical practice.

TBI-Containing with T-Cell Replete Full Haplotype Mismatched Hematopoietic Stem Cell Transplantation in Adult Patients with De Novo Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the 2nd most frequent developing hematologic malignancy with deep heterogeneity, but unfortunately the majority of patients relapse even after allogeneic hematopoietic stem cell transplantation (HSCT) in complete remission (CR). We have developed allogeneic HSCT from familial mismatched/haploidentical donors (FMT) in adult patients with a single disease entity of AML lacking of both HLA-identical siblings and well-matched unrelated donors (WMUD) from the mid 1990s. Previously, several pilot studies of FMT performed with various total body irradiation (TBI)-based conditioning regimens (2~12 gray) with or without post-transplant cyclophosphamide (PT-Cy) as a graft-versus-host disease (GvHD) prophylaxis were reported. Here, we demonstrate about the encouraging outcomes of FMT using unmanipulated peripheral blood donor stem cells (PBSCs) and de-escalated dose of TBI (4~8 gray) containing conditioning regimen without T-cell depletion manner. Although PT-Cy as a specific GvHD prophylaxis regimen is increasingly used for both adult and pediatric FMT, our group investigated the clinical outcomes in adult patients with de novo AML who received full haplotype mismatched HSCT after TBI containing preparation regimen consisted of fractionated TBI (total 4 gray for elderly and 8 gray for <60 years old), fludarabine (150 mg/m 2/day), busulfex (6.4mg/kg/day), and anti-thymocyte globulin (ATG). For GvHD prophylaxis, rabbit ATG (thymoglobulin, Genzyme, 1.25mg/kg/day for 4 days at D-4 to D-1) and a combination of tacrolimus and short-term methotrexate was used. G-CSF mobilized unmanipulated PBSCs were used with a median CD34+ dose of 6.5 x 10 6/kg (1~25.6). From 2008 to the end of 2022, total 429 adult patients were enrolled, and data demonstrated that our trial of intermediate-dose of ATG and reduced toxicity of TBI-containing conditioning regimen to reduce graft-failure even for high levels of donor-specific antibody titer, early transplant-related mortality, critical cytomegalovirus (CMV) disease, and emerging post-transplant lymphoproliferative disease with rapid immune recovery has shown very successful outcomes. Briefly, the median absolute neutrophil count recovery was 12 days (10~26) and the platelet of 14 days (5~38). There was no either primary or secondary graft-failures at all. With a median follow-up of 36.5 months (2~242) for survivors, overall survival rate (OS) and relapse-free survival (RFS) for patients in any CR (n=338) and relapse/refractory status (n=91) were 62.9% vs. 34.3% and 59.5% vs. 32.2%, respectively. Although there was no significant difference in the subgroup analysis, de novo and young aged patients in any CR showed the best OS 73% (Figure 1). Cumulative incidences of acute GvHD and chronic GvHD were 66% (59-73), 70% (63-76), respectively. The incidences of moderate to severe acute GvHD and chronic GvHD were 16.1%, 30.5%, respectively. By univariate and multivariate analyses, patient's age <54 (p=0.043), pre-HSCT CR1 (p <0.001), absence of mod to severe chronic GvHD (p <0.001), and use of post-transplant iron-chelating agent (p=0.001) were the statistically significant in the study. The GvHD-free and relapse-free survival rate in CR1 was 62.4% for younger patients (age <54) and 47.9% for older patients (p=ns). The non-relapse mortality rate was 27.2% for all enrolled patients and 16% for CR patients. The rapidity of immune recovery was also compared with our old control cohort when we performed T-cell depletion using the CliniMACS system, and it showed a significant reconstitution of CD4+ cells (>300/ul) at 3 months post-FMT compared to the much delayed T-cell depleted FMT. Of note, CMV DNAemia was relatively higher (76.9%) than reported in other studies, likely due to the use of ATG and the endemic region of our country. Therefore, we suggest that the strategic reduction of fractionated TBI 4~8 gray-based conditioning with unmanipulated PBSCs graft without PT-Cy seems feasible with favorable outcomes for adult patients with de novo AML undergoing FMT in CR, especially even in a certain subgroup of elderly patients with AML.

Comparison of Autologous, Matched Sibling, and Alternative Donor Stem Cell Transplant Outcomes for Acute Myeloid Leukemia Patients in First Remission: A Propensity Score Matching Study

Introduction Autologous hematopoietic stem cell transplantation (auto-HSCT), matched sibling donor HSCT (MSD-HSCT), and alternative donor HSCT (AD-HSCT) are viable post-remission treatment options for acute myeloid leukemia (AML). Auto-HSCT is more commonly administered in favorable- and intermediate-risk AML with good remission, while MSD-HSCT and AD-HSCT are suggested for patients with high-risk factors. In the present study, we aim to retrospectively compared auto-HSCT with MSD-HSCT and AD-HSCT in de novo AML patients who are in first complete remission (CR1) with favorable or intermediate risk, according to 2022 ELN criteria. Methods We conducted a single-center retrospective comparative analysis, comparing auto-HSCT and allo-HSCT for favorable and intermediate-risk de novo AML in CR1. Patients with secondary AML, acute promyelocytic leukemia, poor-risk AML, those receiving syngeneic HSCT, those not in CR1 before HSCT, or those who achieved CR1 with ≥ 3 cycles of induction chemotherapy were excluded from the study. A total of 283 de novo favorable- and intermediate-risk AML patients, based on the ELN 2022 criteria, in first complete remission were initially included for propensity score matching. Persistent undetectable MRD (uMRD) was defined as uMRD after one course of chemotherapy without recurrent positive MRD before HSCT, while non-persistent uMRD was characterized by the presence of detectable MRD at least once before HSCT. The variables used for propensity score matching included induction chemotherapy cycles, consolidation chemotherapy cycles, and measurable residual disease (MRD) measurement by flow cytometer before HSCT. A caliper width of 0.2 was used. Following the matching process, 126 patients were selected for further analysis, with 42 patients in each of the auto-HSCT, MSD-HSCT, and AD-HSCT groups. Results After applying propensity score matching, a final cohort of 126 patients was available for analysis. This cohort consisted of 42 patients in each group: auto-HSCT, MSD-HSCT, and AD-HSCT. Among the AD-HSCT group, 38 of 42 (90.5%) patients received haploidentical HSCT (haplo-HSCT). All patients received myeloablative conditioning regimen. There were no significant differences observed in the 3-year overall survival (OS) and disease-free survival (DFS) among the auto-HSCT, MSD-HSCT, and AD-HSCT groups [3-year OS: 79.5% (95% CI, 67.8-93.3%), 83.0% (95% CI, 72.2-95.3%), and 65.7% (95% CI, 50.5-85.5%), respectively; P=0.21. 3-year DFS: 72.6% (95% CI, 59.9-87.9%), 83.0% (95% CI, 72.2-95.3%), and 67.5% (95% CI, 54.2-84.1%), respectively; P=0.32]. The cumulative incidence of 3-year NRM was 2.7% (95% CI, 2.0-12.5%), 7.3% (95% CI, 1.8-17.9%), and 21.9% (95% CI, 10.7-35.6%), respectively (P=0.008). The 1-year probability of OS after relapse was higher in the auto-HSCT group (44.4%; 95% CI, 21.4-92.3%) compared with MSD-HSCT (0.0%) and AD-HSCT (37.5%; 95% CI, 8.4-99.9%) (P=0.0017). The MRD status before HSCT had an impact on DFS (persistent uMRD versus non-persistent uMRD: HR=0.29; 95% CI 0.09-0.94, P=0.04) and relapse (persistent uMRD versus non-persistent uMRD: HR=0.17; 95% CI 0.05-0.66, P=0.01) following auto-HSCT. The subgroup analysis was then performed based on MRD status before HSCT. In patients with uMRD before transplant (n=83), OS was similar across the groups. However, auto-HSCT showed a trend of increased DFS compared to AD-HSCT (HR 2.85, P=0.09), resulting in a 3-year DFS and OS of 79.1% and 82.8%, respectively. In the non-persistent uMRD group (n=38), auto-HSCT exhibited a tendency to increase the risk of relapse, particularly when compared to AD-HSCT (HR 0.24, P=0.07), but this did not result in inferior OS. The monthly direct medical cost per patient within the first two years after HSCT was significantly lower in auto-HSCT compared to MSD-HSCT (P=0.015) and AD-HSCT (P<0.001). Conclusions Our results provide evidence for the use of auto-HSCT as a viable therapeutic option for favorable- and intermediate-risk de novo AML patients in first complete remission with persistent uMRD. Additionally, our findings demonstrated a notable cost advantage associated with auto-HSCT compared to MSD-HSCT and AD-HSCT.

Outcome of Multiple Myeloma Patients Undergoing Allogeneic Stem Cell Transplant with Post-Transplant Cyclophosphamide - a Single Center Experience

Objective: The survival of multiple myeloma (MM) patients has improved significantly in the past decade with the development of new effective treatments including immunomodulators, monoclonal antibodies, and chimeric antigen receptor T cell (CAR-T) therapy. However, to date, none of the available treatments is curative for MM. In high-risk and relapsed patients, allogeneic stem cell transplant (allo-SCT) achieved long term survival in carefully selected MM patients. Here, we report our experience in MM patients who received allo-SCT at Thomas Jefferson University Hospital (TJUH). We aim to define the role of allo-SCT in the new era of MM treatment. Method: We retrospectively analyzed data of 57 MM patients who received allo-SCT at TJUH from 1996-2023. We used EZR software to analyze post-transplant outcomes including overall survival (OS) and disease-free survival (DFS) with Kaplan Meier method. Cumulative incidence (CI) calculated by EZR was used to determine relapse rate (RR) and non-relapse mortality (NRM). Median time to neutrophil and platelet engraftment was analyzed by Excel 2022. Results: The median age was 53 years old (range from 34-68 years old); 29 females and 28 males. Mean follow up time was 57.9 months (range from 0 to 253.6 months). Thirty-two patients received reduced intensity conditioning, 11 patients received myeloablative conditioning regimen, and 5 patients received non-myeloablative conditioning regimens. Thirty-one patients received matched related donor (MRD), 3 patients received matched unrelated donor (MUD), 21 patients received haploidentical (HI), and 2 patients received mismatched unrelated donor stem cell grafts. Time to neutrophil and platelet engraftment data was available for 33 and 29 patients, respectively. The median time to neutrophil engraftment was 12 days (range from 3-23 days). and the median time to platelet engraftment was 16 days (range from 6-51days). The 3-year and 5-year probabilities of OS were 53.2% (95% confidence interval is 38.7% to 65.7%) and 48.3% (95% confidence interval is 33.9% to 61.3%) respectively. The 3-year and 5-year probability of DFS were 37% (95% confidence interval is 21.6% to 52.5%) and 26.2% (95% confidence interval is 12.6% to 42%) respectively. Since 2009, most of the patients (33/36) in this study received post-transplant cyclophosphamide. Thus, we compared the OS for patients who received allo-SCT before 2009 and after 2009. The 5-years OS was 28.6% (95% confidence interval is 7.8% to 42.5%) and 62.7% (95% confidence interval is 43% to 77.2%) for patients who received allo-SCT before 2009 and after 2009 respectively (P=0.029). Among 43 patients with available relapse date data, the CI of relapse at 3 years was 36.9% (95% confidence interval 21.5%-52.4%) and the CI of NRM at 3 years was 26.1% (95% confidence interval 14%-39.9%). Thirty-five patients were evaluable for acute graft versus host disease (GVHD). Nine patients developed grade I-IV acute GVHD (25.7%) and 2 patients experienced grade III-IV acute GVHD (5.7%). Four out of 35 evaluable patients experienced chronic GVHD (11.4%): 2 patients had mild to moderate scleroderma, one patient had severe chronic skin GVHD and one had severe lung chronic GVHD. For 36 patients received allo-SCT after 2009, 3 died from relapse, 3 patients died from infection, 2 died from GVHD, 2 from unknown cause, one from brain bleeding, one from non-infectious pulmonary failure and one from acute heart failure. Conclusion: In MM patients with high-risk feature or relapsed/refractory disease, allo-SCT can be curative for approximately a third of the patients. Post-transplant cyclophosphamide coupled with contemporaneous MM treatments significantly increased the survival of allo-SCT MM patients in the modern era.

Upfront Allogeneic Hematopoietic Stem Cell Transplantation Can Provide Survival Benefit Versus Hypomethylating Agent in Myelodysplastic Syndrome with Increased Blasts I (MDS-IB I)

Introduction Myelodysplastic syndrome (MDS) is a group of clonal disorders of hematopoietic stem cell. Survival would be significantly shortened if excessive blasts appear in marrow or the periphery. As disease progression accelerating, about 25% of MDS-IB1 and 33% of MDS-IB2 patients were reported to finally transformed into leukemia. Currently, allogeneic stem-cell transplantation (Allo-HSCT) still remains the only curable treatment accompanied with risk of therapy related mortality and decline of life quality. Decitabine (DAC), an of DNA methylation, was also reported to exhibit benefit in treatment of MDS. Thus, comparative studies with allo-HSCT are needed. Objective To retrospectively compare response of upfront allogeneic HSCT with hypomethylating agent (DAC in 87.5% of the group) therapy according to stem-cell donor availability in patients with MDS-IB1. Methods We retrospectively reviewed 103 patients with primary MDS patients who were evaluated and received treatment in our center between August 2011 and August 2020.Overall survival (OS) , event-free survival (EFS), non-relapse mortality (NRM) and cumulative rate of relapse or progression (CIR) at 1 year was calculated according to treatment arm.Cox regression analyses with allo-HSCT as time-dependent covariate (Mantel-Byar approach) were performed. Results According to the International Prognostic Scoring System (IPSS), 55 patients (55%) were stratified into lower-risk and 46 patients (45%) were stratified into higher-risk (IPSS intermediate 2 or high risk). Allogeneic HSCT was performed in 61.2% (n=63) and the rest 38.8% (n=40) received continuous HMA. In the no-donor group, 28 patients (70%) experienced disease progression or relapse after remission and leukemia transformation was noted in 14 patients (35%). The median follow-up time for surviving patients was 30.4months (range: 3.2-122.1 months). In the entire cohort, non-relapse mortality rate at 1 year was significantly higher in the allo-HSCT group compared with HMA group (14.3% vs. 2.5%, P=0.008), and the cumulative incidence of relapse and progression at 1 year was significantly lower (1.6% vs. 45.5%, P<0.001). After matching with propensity-score, the overall survival rate at 3 years was 77.8% in the allo-HSCT group compared with 43.5% in the HMA group with a significant difference by Cox-regression considered allo-HSCT as time-dependent covariate ( P=0.045), and event-free survival rate at 3 years was higher in allo-HSCT patients (73.4%) compared with HMA group (20.6%; P=0.001). The advantage of allo-HSCT was seen in those who aged > 50 years, male, those with ineffective erythropoiesis and without iron overload. Conclusion We concluded that patients with MDS-EB1 significantly benefited from receiving allo-HSCT with prolonged OS and EFS compared with continuous HMA (DAC) therapy. The advantage of allo-HSCT has been seen in subgroups of patients who age >50 years, male, those with ineffective erythropoiesis and without iron overload. Even earlier myeloablative allo-HSCT prevents further progression of MDS-EB1 at risk of higher non-relapse mortality, upfront allo-HSCT should be considered in a donor available scenario.

Phase 1/2 Study of Donor-Derived Anti-CD33 Chimeric Antigen Receptor Expressing T Cells (VCAR33) in Patients with Relapsed or Refractory Acute Myeloid Leukemia after Allogeneic Hematopoietic Cell Transplantation

Background and Significance: Although allogeneic hematopoietic cell transplantation (alloHCT) is a potentially curative therapy for patients with high-risk acute myeloid leukemia (AML), relapse occurs in 30% to 40% of alloHCT recipients and is associated with a 2-year post-relapse survival rate of less than 20%. Chimeric antigen receptor (CAR) T cells targeting tumor-associated antigens have demonstrated efficacy in relapsed/refractory (R/R) acute lymphoblastic leukemia and other hematologic malignancies, but there is limited clinical experience with CAR T cell therapies for AML. Current challenges for autologous AML CAR T cell therapy include the inability to harvest adequate numbers of functional, undifferentiated T cells as CAR T cell starting material. In addition, the potential presence of AML blasts in an autologous cell collection can interfere with T cell proliferation and function during the manufacturing process. To circumvent these impediments in patients with R/R AML after alloHCT, VCAR33 represents a CD33-directed CAR T cell product generated from lymphocytes from each patient's prior allogeneic stem cell donor. CAR T cell manufacture from HLA-matched donors will likely not only eliminate delays and failures in production due to lymphopenia but also improve T cell function by using healthy starting material. CD33 is a preferential target for AML CAR T cell therapy as it is expressed on the majority (>80%) of AML blasts and because prior clinical experience with gemtuzumab ozogamicin (GO; tradename: Mylotarg TM) has demonstrated the safety and efficacy of targeting CD33. Study Design and Methods: Study NCTxxxxxxxx* is a multi-center phase 1/2 study evaluating the safety and preliminary efficacy of VCAR33, donor-derived allogeneic CAR T cells targeting CD33 (Figure 1). The CAR construct used for the manufacture of VCAR33 contains a lintuzumab-derived binding domain and a CD28 co-stimulatory domain. Key inclusion criteria include adult patients with relapsed or measurable residual disease positive (MRD+) AML after undergoing alloHCT with an 8/8 HLA-matched related or unrelated donor. Patients who have undergone alloHCT with trem-cel, a CD33-deleted allogeneic stem cell product intended to facilitate the post-HCT treatment with CD33-directed therapies by reducing on-target off-tumor hematotoxicity, may also participate. Patients will be assigned to one of two study arms based on their AML disease burden: Arm A for morphologic disease with ≥ 5% blasts in the bone marrow, or Arm B for MRD+ defined as < 5% blasts in the bone marrow with ≥ 0.1% CD33+ leukemia cells by flow cytometry. The patient's prior stem cell donor undergoes apheresis for collection of mononuclear cells, which are used as starting material for VCAR33 manufacturing. Patients will receive lymphodepletion on days -5 to -2 with fludarabine (total 120 mg/m 2) and cyclophosphamide (total 1000 mg/m 2) followed by infusion of VCAR33 on Day 0. Each study arm will enroll and escalate independently according to a standard 3+3 trial design, starting at 1 x 10 6 CAR T cells/kg for Dose Level 1. The dose limiting toxicity monitoring period is 28 days, at which time patients will undergo evaluation of disease response. Secondary endpoints include incidence of cytokine release syndrome, graft-vs-host disease, and clinical response. Exploratory endpoints aim to correlate VCAR33 properties with clinical response by characterizing T cell phenotypes within the VCAR33 product and by examining VCAR33 expansion and persistence after infusion. Follow up on trial will continue for up to 2 years after infusion followed by long term monitoring for up to 15 years. Patients may undergo second alloHCT for consolidation of remission or for rescue of prolonged cytopenia due to on-target off-tumor effects of VCAR33. *NCT number pending. Clinical trial information submitted to CT.gov on July 19, 2023.

Outcome of Allogeneic Stem Cell Transplantation in FLT3-TKD-Mutated AML - a Study on Behalf of the Acute Leukemia Working Party of the EBMT

Introduction The overall prognostic impact of point mutations in the tyrosine-kinase domain 1 of FLT3 (FLT3-TKD mut) in patients (pts) with acute myelogenous leukemia (AML) remains controversial. Furthermore, co-occurrence of FLT3-TKD mut and mutated nucleophosmin-1 (NPM1 mut) was shown to have a favorable prognostic impact on AML pts receiving conventional chemotherapy. However, little is known about the outcome of AML pts with FLT3-TKD mut with or without co-occurring NPM1 mut treated with allogeneic stem cell transplantation (alloSCT). Patients and Methods This is a retrospective study of the acute leukemia working party (ALWP) of the European Society for Blood and Marrow transplantation (EBMT) investigating the outcome of adult AML pts with FLT3-TKD mut with or without NPM1 mut after first alloSCT using matched sibling (MSD), unrelated (UD) or haploidentical (haplo) donors between 2005 and 2022. All patients were in first or second complete remission (CR1 of CR2). Information on cytogenetic risk was necessary for inclusion. No ex-vivo T-cell depletion (TCD) was allowed. The primary endpoint was leukemia-free survival (LFS) at two years after alloSCT. Secondary endpoints were overall survival (OS), cumulative incidence of relapse (RI), non-relapse mortality (NRM), acute and chronic graft-versus-host disease (GVHD) and GVHD-free, relapse free survival (GRFS). One hundred and eighty-two adult AML pts with FLT3-TKD mut were identified, of which 74 (40.7%) had a co-occurring mutation in NPM1. Median age was 55.1 years (range 18.6-79.1) and 46.7% were male. Median follow-up was 21.4 months [IQR 13.6-28.1]. 78% of the pts were in CR1. Cytogentic risk was favorable, intermediate and adverse in 12.6%, 75.3% and 12.1% of pts, respectively. Additional FLT3 internal tandem duplication (FLT3-ITD) was present in 25.8% of pts. Information on measurable residual disease (MRD) was available for 68.7% of pts, being positive in 48% of these. Karnofsky performance score was < 90% in 21.1%, and hematopoietic cell transplantation-specific comorbidity index (HCT-CI) was >=3 in 28.1% of pts. 69.6% of pts were cytomegalovirus (CMV) positive. Conditioning was myeloablative in 52.8% and reduced intensity in 47.2% of pts. Stem cell donors were MSD, UD and haplo in 25.8%, 55.5% and 18.7% of cases. Stem cell source was bone marrow in 10.4%, peripheral blood in 87.4% and both in 2.2%. In-vivo TCD was performed in 59.2% of pts. GVHD prophylaxis was calcineurin inhibitor-based in 92.2% of pts. Results Engraftment was achieved in 99.4% of pts with a day-60 absolute neutrophil count (ANC) >0.5 x 10 9/L of 97.7% [95% CI: 93.7-99.2]. Day-180 rates of acute GVHD (aGVHD) grade II-IV and grade III-IV were 26.2% (95% CI:19.9-32.9) and 8.1% (95% CI:4.6-12.8), respectively. At two years, rates of total chronic GVHD (cGVHD) and extensive cGVHD were 30% (95% CI: 22.5-38) and 16.6% (95% CI:10.6-23.7), respectively. Two-year LFS and OS were 66.1% (95% CI: 57.6-73.2) and 74% (95% CI: 65.4-80.8), respectively. Two-year RI, NRM and GRFS were 22.5% (95% CI:16-29.8), 11.4% (95% CI: 7-17), and 51.1% (95% CI: 42.4-59.1), respectively. Cause of death was original disease in 47.5%, infection in 27.5%, GVHD in 22.5% and non-SCT related in 2.5% of cases. In univariate analysis the only factor with significant impact on LFS was donor type (haplo [n=34] vs. others, p=0.006). For GRFS, patient CMV negativity (p=0.014) and in-vivo TCD (p=0.01) were significant. Interestingly, co-occurring mutations in FLT3 (FLT3-ITD) or NPM1 were not identified as having a significant impact on LFS or GRFS. Moreover, MRD status before alloSCT was also not shown to have a significant impact on these outcomes. In multivariate analysis of LFS and GRFS, only donor type (haplo [n=34] vs. others) was shown to be significant for both endpoints, hazard ratio (HR) 2.54; 95% CI: 1.4-4.6; p=0.002, and HR 2.01; 95% CI: 1.18-3.41; p=0.01, respectively. Conclusion Acknowledging the limitations of our retrospective study in this rare entity results are encouraging given the high-risk population (median age 55.1 years, CR2 in 22%, co-occurring FLT3-ITD in 25.8%, positive MRD in 48%, HCT CI >=3 in 28.1%). LFS, OS and GRFS rates were 66.1%, 74% and 51.1%, respectively, and both RI and NRM were comparably low with rates of 22.5% and 11.4%, respectively. No positive prognostic impact of co-occurring mutations in FLT3-TKD and NPM1 was detected, unlike what was found for conventional chemotherapy.

Unrelated Donors below 35 Years of Age Should be Preferred over HLA-Matched Sibling Donors Older Than 50 Years for Patients with Myeloid Malignancies

Introduction. Selecting the best available stem cell donor is crucial to optimize outcome after allogeneic hematopoietic cell transplantation (alloHCT). For several decades, matched sibling donors (MSD) were considered to be the best choice for all patients. Recently published data suggest that young unrelated donors (UD) may represent a favorable alternative. However, analyses in contemporary disease-specific registry cohorts are still rare. Therefore, we set out to investigate whether young UD provide a benefit for older patients with myeloid malignancies compared to MSD. Patients and Methods. We performed a retrospective study with data of the Deutsches Register Stammzelltransplantation (DRST) on patients 50 years and older who received a first alloHCT for AML, MDS, MDS/MPN or CMML between January 2010 and December 2020. We compared results of patients who were transplanted from MSD aged 50 years or older and young UD aged 35 years or younger who were HLA-compatible for HLA-A, -B, -C, and -DRB1. We evaluated the primary endpoint, event-free survival (EFS), and the secondary endpoints overall survival (OS), cumulative incidence of relapse/progression (CIR), non-relapse mortality (NRM), acute and chronic Graft-versus-Host Disease (GvHD) in multivariable Cox regression models. Results. In total, we analyzed data from 3460 patients. Median patient age was 63.5 years for 2225 patients with UD compared to 60.9 years for 1235 patients with MSD (p<.001). The median donor age was 27 years (range 18-35 years) for UD compared to 58 years (range 50-79 years) for MSD (p<.001). Overall, male donors accounted for 77.9% of UD compared to 49.3% of MSD (p<.001). Fewer male patients had female UD than female MSD (8.6% versus 30%, p<.001). Also, more cytomegalovirus (CMV) seronegative patients had CMV seronegative UD (34.9% versus 23%, p<.001). The percentage of alloHCT with UD increased in recent years, from 46% in 2010 to 72% in 2020 (p<.001). HLA-DQB1-mismatches were reported for 2.5% of UD. HLA-DPB1 matching information was available for 33.6% of UD. We found no differences with respect to the distribution of Karnofsky performance status, disease risk, reduced intensity conditioning (circa 80% of patients) and graft source (almost exclusively PBSC) between the two donor types. GVHD prophylaxis differed significantly, more patients with UD received ATG compared to patients with MSD (87.4% versus 52.9%, p<.001). In univariate comparisons, we observed a trend towards improved EFS (HR 0.91, p=.07; Figure Panel A) and improved OS (HR 0.88, p=.03) for UD compared to MSD transplants. CIR was lower with UD (HR 0.87, p=.04, Figure Panel B) and NRM was not statistically different (HR 0.96, p=.6). The 150-days cumulative incidence of aGVHD was 28.2% for UD versus 31.3% for MSD transplants (p=.09). Corresponding numbers for the 1-year cumulative incidence of cGVHD were 31.3% and 39.4% for UD versus MSD transplants (p=<.001). After multivariable adjustment for patient age, performance status, disease risk, conditioning type, stem cell source, and HLA-DQB1-mismatches, EFS and OS were significantly better for 10/10 UD compared to MSD transplantation with hazard ratios (HR) of 0.86 for EFS (p=.003) and 0.82 for OS (p<.001). After UD alloHCT we found a lower risk of relapse (HR 0.84, p=.018), less chronic GVHD (HR 0.7, p<.001) and a trend towards lower NRM (HR 0.87, p=.07). Conclusions. Selecting HLA-compatible UD over older MSD improves the chances of survival (both OS and EFS) after alloHCT for older patients with myeloid malignancies. This beneficial effect was mediated mainly by a reduced risk for relapse/progression suggesting more potent Graft-versus-Leukemia effects after UD transplantation despite less chronic GVHD.

Effectiveness and Safety of Rabbit Anti-Thymocyte Globulin Versus Non-Anti-Thymocyte Globulin Regimens for Graft-Versus-Host Disease Prophylaxis: A Systematic Review and Meta-Analysis

Introduction:Graft-versus-host disease (GVHD) is a serious complication after allogeneic hematopoietic stem cell transplant (HSCT), limiting its success. Meta-analyses have confirmed clinical efficacy and safety of several types of anti-thymocyte globulins (ATGs) in GVHD prophylaxis; however, there are no meta-analyses assessing the efficacy of rabbit anti-thymocyte globulin (rATG; Thymoglobulin ®) in particular. This study assessed the effectiveness and safety of rATG relative to non-ATG prophylaxis regimens for acute GVHD (aGVHD) or chronic GVHD (cGVHD) based on randomized controlled trials (RCTs) and observational studies. Methods:A literature search was conducted in MEDLINE, Embase, Cochrane Central, and the Web of Science using the PICOS framework to identify studies published until June 2022 focusing on the prophylaxis use of rATG in GVHD. The United States and European Union clinical trial registry databases were also searched to identify unpublished data from studies. Efficacy outcomes included incidences of aGVHD (Grade II-IV and Grade III-IV), cGVHD (mild to severe and moderate to severe) and overall survival. Safety outcomes included the incidence of relapse, cytomegalovirus (CMV) infection, and Epstein-Barr virus (EBV) reactivation. Pre-specified subgroups of interest included donor type, and stem cell source (an unrelated peripheral blood [PB]/bone marrow [BM] transplant, a related PB/BM transplant, or a mixed unrelated and related PB/BM transplant). All analyses present the overall effect, the effect by subgroups, and the percentage contributing to the overall effect. Results: Overall, 4295 records were retrieved from the databases and hand searching (1000 from PubMed, 1700 from Embase, 1419 from the Web of Science, 155 from the Cochrane Central, 20 from the clinical trial registry databases and 1 from hand searching). After screening, 45 studies (6 RCTs, 35 retrospective studies and 4 prospective observational studies) published between 2001 and June 2022 were included in this review. Among the 45 studies, 39 reported aGVHD Grade II-IV, 33 reported aGVHD Grade III-IV, 33 reported mild to severe cGVHD, 31 reported moderate to severe cGVHD, and 41 reported overall survival ( Table). Use of rATG for GVHD prophylaxis resulted in a significant 24% reduction in Grade II-IV aGVHD (RR=0.76; 95% CI: 0.68-0.85) and a significant 43% reduction in Grade III-IV aGVHD (RR=0.57; 95% CI: 0.49-0.65) compared with non-ATG arm across all donor types. Similarly, a 35% reduction was observed in mild to severe cGVHD (RR=0.65; 95%CI: 0.57-0.74) and a significant 48% reduction (RR=0.52; 95% CI: 0.45-0.60) was observed in moderate to severe cGVHD across all donor types. Use of rATG decreased overall mortality by 9% (RR=0.91; 95% CI: 0.85-0.99). Among the subgroups, the decrease in mortality was statistically significant in unrelated PB/BM transplant donors. The incidence of relapse was reported in 36 studies, with an overall 18% increase (RR=1.18; 95% CI: 1.08-1.30) for patients treated with rATG. However, among the subgroups, the incidence of relapse was comparable between rATG and non-ATG prophylaxis arms for all types of donors. rATG and non-ATG prophylaxis regimens were comparable in terms of CMV infection (RR=1.00; 95% CI: 0.88-1.15). The incidence of EBV infection was significantly higher in the rATG arm (RR=2.53; 95% CI: 1.54-4.17) than that in the non-ATG arm. Conclusions: This meta-analysis provides useful information to support patients and health-care providers in making treatment decisions for the prevention of aGVHD or cGVHD after allogeneic HSCT. rATG demonstrated significant reductions in the incidence of both aGVHD and cGVHD and increased the overall survival across donor types and stem cell sources despite slightly increased risk of relapse in rATG arm versus non-ATG arm.

Detectable Somatic Variants Using Next Generation Sequencing (NGS) Post Allogeneic Hematopoietic Cell Transplant (Allo-HCT) Predict for High Relapse Risk in Acute Myeloid Leukemia (AML) and Myelodysplastic Syndromes (MDS)

Introduction: NGS is increasingly being utilized to identify pathogenic somatic and targetable variants in patients with newly diagnosed AML and MDS. Patients with high-risk disease are typically recommended to undergo allo-HCT as consolidation, upon achieving morphological complete remission (CR). But, despite achieving hematologic CR, patients often have detectable somatic variants pre allo-HCT that predict for increased risk of disease relapse. Longitudinal monitoring of somatic variants via NGS at diagnosis, pre-allo-HCT and post allo-HCT can assist in prognostication and identify patients that remain at high risk of relapse despite allo-HCT. Methods: Patients with AML or MDS who underwent a first allo-HCT and completed NGS testing at day +100 between years 2016 to 2021 were identified from the transplant registry of Mayo Clinic in Florida. The primary aim of the study was to evaluate the prognostic impact of detectable variants via NGS at day +100 days post allo-HCT on the following outcomes: 1) overall survival (OS), 2) relapse, 3) progression-free survival (PFS), and 4) non-relapse mortality (NRM). Disease risk was assessed based on European Leukemia Network (ELN) 2022 risk classification for AML and Revised International Prognostic Scoring System (R-IPPS) for MDS. Baseline variables were compared between patients with and without mutation at day +100 days post allo-HCT using Wilcoxon rank sum test for continuous variables and Fisher's exact test for categorical variables. Kaplan-Meier (KM) method was used to estimate freedom from events at different time points and draw corresponding survival curves. Results: 105 patients who underwent allo-HCT for AML and MDS and completed NGS testing at day +100 were included in the study population. Median age of the study population was 63 years (22-74) and 58% were of the male gender. Median HCT comorbidity score (HCT-CI) and KPS Karnofsky performance score (KPS) were 3 (0-8) and 90 (60-100), respectively. Matched unrelated donor (50%) and peripheral blood stem cells (98%) were the most common donor and graft source, respectively. Median number of lines of therapy pre allo-HCT was 1(0-6) and 52 (50%) patients had detectable variants after completion of chemotherapy and prior to allo-HCT. Seventeen (16%) had detectable variants via NGS on day +100. Eleven (65%) of these 17 had variants pre-allo-HCT and amongst the 88 patients with no variants post allo-HCT, 41 (47%) had detectable variants pre allo-HCT. There was no significant difference in baseline characteristics between patients with detectable variants at day+100 versus those who did not except for a higher KPS in patients with no variants at Day +100 of 90 (60-100) vs. 80 (60-100) (p=0.003). At a median follow up of 1.4 years (0.1-5.5), presence of a variant at day +100 was associated with inferior 4-year OS (32% vs. 69%, p<0.001) and higher relapse risk (64% vs. 23%, p<0.001). In univariate models, a lower KPS and presence of variants post allo-HCT were significantly associated with inferior OS, high relapse risk and worse PFS. Presence of variants pre allo-HCT was associated with an inferior PFS but did not impact OS or relapse risk. In multivariate models, KPS remained significant for OS, PFS and NRM; presence of variants at day +100 post allo-HCT approached significance for OS (p=0.06) and PFS (p=0.08) and was significant for relapse risk (p=0.002) (Table1) (Figure 1). Data regarding longitudinal evolution of variants and impact of individual variants on long term outcomes will be included at the time of presentation. Conclusion: These results indicate that presence of detectable somatic variants at day +100 is associated with poor long-term outcomes and predicts for high risk of disease relapse. Longitudinal monitoring of somatic variants via NGS should be consistently incorporated in the management of patients with high-risk AML and MDS undergoing allo-HCT. Patients with detectable somatic variants post allo-HCT should be considered for additional intervention to mitigate relapse risk.

Identification and Validation of Ferroptosis-Related Genes As Novel Prognosis Prediction Panel for Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a main type of adult acute leukemia, especially in elderly population. The development of AML ascribed to various factors including chromosomal abnormalities, isolated gene mutations, etc. and the 5-year survival rate is around 30%. Currently, the most popular and precise assessment of AML is based on cytogenetic differences, and the patients with higher risk molecular mutations had inferior prognosis. However, with the development and application of new drugs, including bcl-2 inhibitors, many AML with high risks (such as FLT3, P53 mutated) also achieve better remission and longer survival. Up to date, many novel prognosis models are in process, with the better understanding of the initiation and development of leukemia. Ferroptosis, a widespread and ancient form of cell death driven by iron-dependent phospholipid peroxidation. Its involvement in AML has been reported, as leukemic cells frequently exhibit enhanced iron uptake and reduced iron efflux, resulting in elevated intracellular iron levels. Targeting iron homeostasis and inducing ferroptosis may provide novel insights into AML therapy. Herein, we integrated multi-gene information to identify a novel prediction model for ferroptosis-related genes (FRGs), and validated the accuracy of the model using clinical samples from our center (Figure A). In this study, we downloaded RNA-seq data and clinicopathological features of 151 AML patients from The Cancer Genome Atlas (TCGA) database (https://www.cancer.gov/ccg/research/genome-sequencing/tcga) and 70 corresponding health samples from the Genotype-Tissue Expression (GTEx) database (https://gtexportal.org/). Retrieve the ferroptosis-related genes (FRGs) set from the FerrDb database (http://www.zhounan.org/ferrdb/current/). The difference analysis, LASSO regression and Cox regression were used to determine the FRGs signature to construct prognostic models (Figure B). We finally identified 10 FRGs signature (ACSF2, SOCS1, CDO1, MYB, LPIN1, DNAJB6, PSAT1, GPX4, MT1G, FH) to establish a risk scoring model, and AML patients were divided into high-risk and low-risk group according to the median risk score. The risk score for each sample was determined using the following formula: . Kaplan-meier analysis showed that the overall survival of patients in the high-risk group was significantly worse( P<0.001) (Figure C). Cox regression analysis, ROC and DCA results found that these features have good predictive ability for prognosis of AML (Figure D-F). We also grouped the TCGA AML patients into poor/adverse and favorable/intermediate group based on NCCN guideline (risk stratification based on genomic mutation background), and found that the survival differences based on classical risk model were not that obvious ( P=0.062) (Figure G) when compared to our model ( P<0.001 in Figure C). Which suggested that our model may have its superior in distinguishing real high risk AML patients. In order to validate the accuracy of our model, we also conducted a retrospective study on 30 AML patients and 13 healthy controls (bone marrow stem cell donor) from September 2019 to September 2022. Bone marrow mononuclear cells (BMNC) from our biobank were obtained, and the ten FRGs panel was applied. Results indicated that there was a significantly difference between normal control and AMLs in FRGs expression (Figure H), and the survival data of high-risk AML patients with higher FRGs level was significantly inferior than that in low-risk group as expected ( P<0.05) (Figure I). To search for possible therapeutic drugs for high-risk patients, we downloaded AMLs data from the GDSC database (https://www.cancerrxgene.org/) and calculated the IC50 of commonly used chemotherapeutic drugs. We found that bcl-2 inhibitor (Obatoclax Mesylate) and TKI (Gefitinib) may have less sensitivity in our high-risk group ( P<0.05), while some unconventional drugs (paclitaxe, dactinomycin, camptothecin, irinotecan and vinorelbine) may benefit in patients with higher FRGs expression (Figure J). In summary, we identified and validated 10 FRGs signature to well predict the prognosis and drug sensitivity of AML. Based on our findings, appropriate combination of new drugs at the time of treatment may achieve unexpected therapeutic outcomes, but still need to go through further verification.

Constructing a Machine Learning-Based Rating Model to Predict the Outcome of GCSF Mobilization of Hematopoietic Stem Cells in Peripheral Blood

Objective Peripheral blood stem cells serve as the primary source of hematopoietic stem cells for both autologous and allogeneic stem cell transplantation. Granulocyte colony-stimulating factor (G-CSF) stands as the most commonly employed mobilizing agent in clinical practice. While the majority of donors receiving G-CSF mobilization demonstrate high mobilization efficiency, there remains a subset of donors who fail to yield a sufficient quantity of hematopoietic stem cells. Inefficient mobilization not only leads to wastage of valuable resources but also significantly impacts transplant outcomes for recipients. Therefore, addressing the challenges associated with predicting mobilization outcomes, optimizing donor selection strategies, and further enhancing mobilization approaches is of paramount importance. Methods In this study, we conducted a retrospective analysis of mobilization data from 1008 donors who underwent hematopoietic stem cell mobilization using G-CSF at the Bone Marrow Transplantation Center, the First Affiliated Hospital, Zhejiang University School of Medicine, over the past 5 years. We meticulously examined the correlation between mobilization outcomes (quantified by the quantity of collected CD34+ cells) and various factors, including mobilizing agent usage, demographic data, complete blood count, and blood biochemistry. Furthermore, we harnessed the power of machine learning algorithms, such as linear regression, decision tree, and AdaBoost, to develop a robust scoring model capable of predicting mobilization outcomes. The primary objective of this model is to furnish a predictive tool for assessing mobilization outcomes with accuracy and precision. Results (1) Prior to receiving G-CSF, several factors exhibited a significant positive correlation with the quantity of CD34+ cells in the collection: donor's body weight (R=0.37, p<0.001), peripheral blood leukocytes (R=0.24, p<0.001), hemoglobin (R=0.23, p<0.001), monocytes (R=0.22, p<0.001), lymphocytes (R=0.18, p<0.001), platelets (R=0.18, p<0.001), red blood cells (R=0.12, p<0.001), neutrophils (R=0.15, p<0.001), hematocrit (R=0.21, p<0.001), mean corpuscular-hemoglobin concentration (R=0.15, p<0.001), low-density lipoprotein (R=0.11, p<0.01), albumin (R=0.09, p<0.05), ferritin (R=0.19, p<0.001), triglycerides (R=0.17, p<0.001), creatinine (R=0.17, p<0.001), and uric acid (R=0.29, p<0.001). (2) Age exhibited a significant negative correlation with the quantity of collected CD34+ cells in the collection (R=-0.11, p<0.001). (3) When the total dose of G-CSF administration was fixed, mobilization with twice-daily dosing yielded superior results compared to once-daily dosing (collected CD34+ cell count: 1268/μl vs. 1044/μl, p<0.001). (4) The ratio of G-CSF dosage to body weight demonstrated a significant negative correlation with the quantity of CD34+ cells (R=-0.09, p<0.01). Mobilization with a ratio of 6-7 μg/kg/day showed better results compared to a ratio of 7-12 μg/kg/day (p=0.07). (5) A scoring model was developed using machine learning methods to predict the mobilization outcomes of donors. Validation on the test dataset exhibited a high predictive ability of the model (AUC>0.7). Conclusion This study provides valuable insights for selecting hematopoietic stem cell donors and serves as a reference for future strategies aimed at improving mobilization outcomes. The identified factors, such as donor weight, peripheral blood parameters, G-CSF dosing regimen, and the ratio of dosage to body weight, can be considered when selecting donors and optimizing mobilization protocols. By incorporating machine learning techniques, a scoring model was developed, demonstrating a high predictive ability that can assist in forecasting mobilization outcomes for potential donors. These findings contribute to the optimization of donor selection and mobilization strategies.

Cytomegalovirus-Seronegative Plus Leukoreduced Blood Products Are Still Superior to Only Leukoreduced Products in Preventing Transfusion-Transmitted Cytomegalovirus Infection

Introduction Cytomegalovirus (CMV) is one of the most important pathogens causing complications after hematopoietic stem cell transplantation (HSCT). Transfusion-transmitted CMV infection (TT-CMV) in CMV-seronegative patients is a major issue. Leukoreduced (LR) blood products were unavailable before 2004. However, they have gradually become widespread, and all blood products in Japan have been LR since 2007. This study aimed to assess the incidence of TT-CMV in CMV-seronegative HSCT recipients undergoing autologous HSCT (auto-HSCT) or allogeneic HSCT (allo-HSCT) from CMV-seronegative stem cell donors, who received transfusions with “CMV-seronegative products” from CMV-seronegative donors or “random donor products” from donors not tested for anti-CMV antibodies during the periods of availability and unavailability of LR products. Methods We retrospectively evaluated 3590 CMV-seronegative recipients registered in the TRUMP database of the Japanese Society for Transplantation and Cellular Therapy from 1999 to 2018. The recipients undergoing HSCT were categorized into three periods: Period A (when LR products were unavailable), 1999-2003 (n = 136); Period B (when there were both non-LR and LR products), 2004-2006 (n = 200); and Period C (when only LR products were available), 2007-2018 (n = 3254). TT-CMV was defined by the presence of CMV antigenemia and/or CMV diseases. This study was approved by the Ethics Committee of Kobe University Hospital and was conducted in accordance with the principles of the Declaration of Helsinki. Results The median age of the patients at HSCT was 40 years (range, 0-79 years). Among auto-HSCT patients (n = 1628) transfused with “CMV-negative products”(CN group) and “random donor products” (RD group), the incidences of TT-CMV in the CN and RD groups were 0% (0/4) and 3.1% (1/32) during Period A (P = 1.0), 22.2% (2/9) and 10.6% (7/66) during Period B (P = 0.29), and 3.8% (4/105) and 5.0% (71/1412) during Period C (P = 0.81), respectively. Among the allo-HSCT patients (n = 1962), the incidences of TT-CMV in the CN and RD groups were 10.0% (3/30) and 27.1% (19/70) during Period A (P = 0.07), 17.9% (5/28) and 29.9% (29/97) during Period B (P = 0.24), and 11.6% (41/355) and 28.0% (387/1382) during Period C (P < 0.001), respectively. During Period C, 99 patients in the CN group always underwent transfusion with leukocyte reduction filters, of which 11 (11.1%) were diagnosed with TT-CMV. In contrast, 202 patients in the CN group always underwent transfusion without the filters, of which 26 (12.9%) were diagnosed with TT-CMV (P = 0.78). In the RD group, 494 patients always underwent transfusion with leukocyte reduction filters, of which 124 (25.1%) were diagnosed with TT-CMV. On the other hand, 807 patients in the RD group always underwent transfusion without the filters, of which 245 (30.4%) were diagnosed with TT-CMV (P = 0.10). Multivariate analysis revealed that random donor products (hazard ratio [HR]: 3.11, 95% confidence interval [CI]: 2.13-4.52; P < 0.001) and age ≥16 years (HR: 2.90, 95% CI: 2.06-4.09; P < 0.001) were associated with an increased risk of TT-CMV in allo-HSCT. No significant difference was observed in the incidence of CMV diseases between the CN group (3.7%; 13/355) and the RD group (3.8%; 52/1382) (P = 1.00). The major CMV diseases included CMV colitis (n = 5) and pneumonia (n = 2) in the CN group, and CMV colitis (n = 30), pneumonia (n = 9), and retinitis (n = 4) in the RD group. Interestingly, among the patients with TT-CMV during Period C, 27/41 patients (65.9%) in the CN group and 333/387 patients (86.1%) in the RD group received early intervention with anti-CMV agents (P = 0.002). The limitation included that complement-fixation test for anti-CMV antibody was used in Japan Marrow Donor Program in this cohort. Conclusion This is the largest study demonstrating that CMV-seronegative plus LR products are still superior to only LR products from random donors in terms of TT-CMV prevention among allo-HSCT CMV-seronegative recipients. However, no significant difference was observed in the incidence of CMV diseases, possibly because of early intervention with anti-CMV agents.

B-Cell Receptor Function and Gene Expression Profiling at Single-Cell Level across the Spectrum from Normal to Neoplastic CD5-Positive B-Cell Compartments in Humans

Antigen-independent, autonomous signalling of the B-cell receptor (BCR) is an oncogenic driver common to all cases and subtypes of chronic lymphocytic leukemia (CLL). We have recently shown that the dominant clonal population of low-count (<500 cells/µL) monoclonal B lymphocytosis (MBL) with CD5 +CD20 lowCD79B low CLL phenotype identified prospectively in healthy siblings of CLL patients also exhibit autonomous BCR signalling, albeit with lower signalling strength than CLL BCR (Quinten et al., Haematologica 2023). To gain further insight into the mechanisms of clonal expansion within the CD5 + B-cell compartment as the possible origin of CLL, we performed single-cell gene expression profiling and exemplary analyses of BCR function in normal CD5 + B cells (CD20 hiCD79B hi) and in CLL-phenotype B cells (CD5 +CD20 lowCD79B low) of healthy siblings of CLL patients in comparison to CLL and high-count MBL cells. Screening of blood samples of 16 sibling stem cell donors of CLL patients by flow cytometry revealed the presence of CD5 +CD20 lowCD79B low B cells at low counts in 5 donors. These cells and normal CD5 +CD20 hiCD79B hi B cells were sorted in parallel, pooled at equal ratios, and analyzed together with CLL B cells from their sibling stem cell recipients and 2 unrelated high-count MBL B cells on two 10X Genomics chips for single-cell 5‘ gene expression and BCR sequencing. Data deconvolution per individual was performed based on expressed SNPs and on the individuals’ HLA types. In a combined 2-dimensional t-SNE plot based on the 2000 most variably expressed genes, the normal CD5 +CD20 hiCD79B hi B cells from all 5 donors clustered distinctly from CLL-phenotype cells from all sources (dotted lines, Figure) and indeed showed significantly higher expression of CD20 and CD79B. Gene set enrichment analysis revealed significant upregulation of the hallmark oxidative phosphorylation gene set in all CLL samples compared to non-CLL B-cell populations. BCR analysis demonstrated clonal dominance of >99% for both Ig heavy and light chains in the 5 CLL samples. In accordance with the indication for allogeneic stem cell transplantation, these CLL BCR were unmutated. In marked contrast, normal CD5 +CD20 hiCD79B hi B cells from the healthy SC donors were also unmutated but completely polyclonal, i.e. no identical BCR was detected in any two cells of this compartment. In 4/5 donors, the CLL-phenotype CD5 +CD20 lowCD79B low compartment contained multiple clonal expansions of various degrees. In one high-count MBL, 17 other B-cell clones with various degrees of low-level expansion coexisted with the >90% dominant MBL clone. BCR from the most dominant and one or more of the less expanded CD5 +CD20 lowCD79B low clones of the healthy donors were tested for autonomous signaling as quantified by BCR-induced calcium flux without experimental cross-linking in murine TKO pre-B cells and compared to BCR from nonexpanded CD5 +CD20 hiCD79B hi cells and from their CLL siblings. Autonomous BCR signaling strength was calculated from the fraction of cells with spontaneous calcium flux above test background and calibrated against calcium flux after BCR crosslinking. CLL and high-count MBL BCR had robust median autonomous BCR signaling of 0.326. Expanded CD5 +CD20 lowCD79B low clones of the healthy donors showed significantly weaker BCR signalling strength of 0.163 (p<0.01; Scatter Plot). BCR signalling in nonexpanded CD5 + B cells appeared weaker than in expanded clones but was clearly above the background of BCR from mature B cells isolated from lymph node biopsies expressing a mutated IgG. In conclusion, the low-count CD5 +CD20 lowCD79B low CLL-phenotype B-cell compartment in healthy adults is composed of multiple, predominantly mutated B-cell clones. Therefore, the term “monoclonal B lymphocytosis” is highly misleading for these B-cell populations and should be avoided. Normal CD5 +CD20 hiCD79B hi B cells are exclusively unexpanded and express unmutated BCR, indicating a naïve status. Unexpectedly, these nonexpanded CD5 + B cells express BCR with relatively weak but quantifiable autonomous signalling. Globally, autonomous BCR signalling strength across the CD5 + B-cell compartment appears to be correlated to the degree of clonal expansion. Fully malignant CLL cells overexpress genes of the oxidative phosphorylation pathway, presumably to meet increased energy demand from alternative sources.

Combining Low-Dose Post-Transplant Cyclophosphamide(PTCY) with Anti-Thymocyte Globulin(ATG) for Prophylaxis of Graft-Versus-Host Disease in Alternative-Donor Hematopoietic Stem Cell Transplantation for β-Thalassemia Major

Background ： The 5-year overall survival rate (OS) for children with thalassemia major who undergo allogeneic stem cell transplantation is 90% and the event-free survival (EFS) rate is 86%. Due to the limited availability of matched sibling donors, the proportion of transplantations from alternative donors is increasing, particularly from haplo-identical donors. Post-transplant infections and graft-versus-host disease (GVHD) remain the major causes of mortality, especially in those who receive transplantation from alternative donors. Post-transplant cyclophosphamide (PTCY) has shown outstanding results of GVHD prophylaxis in haploidentical matched related donors transplantation with hematological malignancies. However, there is insufficient clinical evidence for its application in pediatric patients who received transplantation from haplo-identical donors with non-malignant hematological disease. Here, we retrospectively analyzed the results of 40 cases that underwent allogeneic stem cell transplantation from haploidentical matched related donors (Haplo-RD) and unrelated donors (UD) to evaluate the safety and efficacy of the novel regimen in GVHD prophylaxis. Method A total of 40 patients with β-thalassemia major received stem cell transplantation, 10 haploid donors (Group Haplo-RD), and 30 unrelated donors (Group UD). Among Group UD, 15 donors were 1 or 2 HLA locus mismatched, remaining 15 were identically matched. The median age of the patients was 5.5 years, ranging from 2 to 12. The Conditioning regimen mainly consisted of fludarabine, busulfan, cyclophosphamide, and thiotepa. GVHD prophylaxis included ATG 1.5mg/kg×3d, cyclophosphamide (CTX) 25mg/kg×2d, cyclosporin A (CsA), and mycophenolate mofetil (MMF). We analyzed the engraftment rate, GVHD incidence, survival rate, and virus reactivation rate for each group. Results Engraftment rate was 100%, with a median time of 11 (10-15) days for neutrophil implantation and 12 (6-31) days for platelet implantation. All patients achieved complete chimerism on day 30 after transplantation. Three cases (7.5%) suffered from Ⅲ-Ⅳ aGVHD, with one being in the Group Haplo-RD group and two in the Group UD. Four cases (10.0%) of cGVHD were recorded. The overall survival (OS) rate and thalassemia-free survival rate were both 92.5%. In Group Haplo-RD, both the OS and thalassemia-free survival rates were 100%. Eight cases reported cytomegaloviremia but no one developed to CMV disease. The total activation rate for CMV was 20%. Nine cases suffered from BK virus urinary tract infection, resulting in a total activation rate of 22.5%. Detailed results are shown in Table 1 and Figure 1. Discussion Due to the high risk of GVHD and infection, stem cell transplantation from haploidentical and unrelated donors cannot be routine therapy for children with thalassemia major. Standard-dose PTCY regimen significantly increases the risk of CMV and BK infection after transplantation and is not suitable for non-malignant disease. The results have been reported that low-dose PTCY/ ATG can reduce the risk of GVHD as compared with standard-dose ATG in haploidentical donor stem cell transplantation. In our study, the novel GVHD prophylaxis regimen, semi-dose PTCY (25mg/kg×2d) combined with low-dose ATG (1.5mg/kg×3d), was used for stem cell transplantation from haploidentical and unrelated mismatched donors. The incidence of III-IV aGVHD was 7.5% and cGVHD was 10.0%, and there was no rejection of the transplant. The activation rate of CMV and BKV was significantly lower than reported in the literature, and the non-relapse mortality (NRM) after transplantation was significantly reduced. There was no statistical difference in the rate of OS, EFS, aGVHD, and cGVHD between Group Haplo-RD and Group UD. The results provide an effective approach for preventing GVHD and infectious diseases in thalassemia patients who underwent allo-HSCT with high-risk GVHD.

The Impact of Post-Transplant Cyclophosphamide (PTCy) with or without MMF in the Prevention of De Novo and Progressive / Relapsing Chronic Graft-Versus-Host Disease after HLA-Matched Donor Transplant

Background: We previously showed that PTCy/Tac ± MMF is associated with a significant reduction in the rate of chronic graft-versus-host disease (cGvHD) as compared to Tac/MTX after HLA-matched sibling (MSD) but not after HLA-matched unrelated (MUD) donor stem cell transplant (SCT). Notably, ATG was used with Tac/MTX in MUD but not in MSD. [ Transplant Cell Ther. 2022;28(10):695] We aimed to further elucidate the epidemiology of cGvHD with the use of PTCy/Tac by comparing the impact of Tac/MTX vs PTCy/Tac ± MMF on de novo and progressive/relapsing cGvHD. Methods: Recipients of a MSD (Tac/MTX no ATG, or PTCy-based) or MUD (Tac/MTX with ATG, or PTCy-based) peripheral blood SCT between 2015-21 at our institution were eligible. To evaluate the impact of prophylaxis on the incidence of de novo and progressive/relapsing cGvHD, we performed two separate landmark analyses starting 3 months (mo) post-SCT among patients who had not and those who had been diagnosed with acute GvHD (aGvHD) within 3 mo post-SCT, respectively. Patients who died or experienced relapse of malignancy (n=135) or were diagnosed with cGvHD within 3 mo post-SCT (n=13) were excluded from the landmark analyses. There was no difference in the rate of early death/relapse or cGvHD by prophylaxis. Results: 1040 patients met the eligibility criteria. Median follow-up in survivors was 28 mo (IQRT: 18, 50). The cumulative incidence (CumInc) of cGvHD in the Tac/MTX, PTCy/Tac without MMF, and PTC/Tac with MMF groups was 39% (34-45, reference), 20% (14-29, p<0.001) and 20% (13-30, p=0.003) respectively in MSD; and 23% (18-30, reference), 17% (12-26; p=0.2), and 19% (14-26; p=0.6) respectively in MUD. Consistent with our previous findings, within the PTCy/Tac group, MMF was not associated with the overall rate of cGvHD in MSD (HR=1.2, 95% CI 0.6-2.1, p=0.6) or MUD (HR=1.3, 95% CI 0.7-2.2, p=0.4). However, in the current study, stratified analyses performed to evaluate the impact of prophylaxis on the risk of de novo vs progressive/relapsing cGvHD revealed a potential role for MMF in the development of de novo cGvHD. Subsequent results are presented separately for the de novo and progressive/relapsing cGvHD risk cohorts (Table). The de novo cGvHD risk cohort included patients (N=442) who had not been diagnosed with aGvHD within 3 mo post-SCT. AML / MDS (60%) and CML / MPD (16%) were the most common diagnoses. 124 cases of cGvHD were diagnosed 3 -36 mo post-SCT with a CumInc of32% (27-37). In multivariate analysis (MVA), compared to Tac/MTX, the use of PTCy/Tac without MMF (HR=0.3, 95% CI 0.2-0.6, p<0.001) was associated with a significant reduction in the incidence of cGvHD. Such reduction was not observed (Figure) with PTCy/Tac with MMF (HR vs Tac/MTX=1.0, 95% CI 0.6-1.5, p=0.9). Additional independent predictors were myeloablative conditioning (HR=1.9, 95% CI 1.3-2.9, p=0.001) and MSD (HR=1.5, 95% CI 1.2-2.6, p=0.003). Notably, progression-free survival (PFS) was similar in PTCy/Tac/MMF (univariate HR: 0.8, 95% CI 0.5-1.4, p=0.4) vs PTCy/Tac. The progressive/relapsing cGvHD risk cohort included patients (N=450) who had been diagnosed with grade 1 (27%), 2 (59%) or 3-4 (14%) aGvHD within 3 mo post-SCT. AML / MDS (64%) and CML / MPD (14%) were the most common diagnoses. 109 cases of cGvHD were diagnosed 3 -36 mo post-SCT with a CumInc of 28% (24-33). In MVA analysis, the impact of prophylaxis differed by donor type. As compared with Tac/MTX, PTCy/Tac ± MMF was associated with significantly lower rate of progressive/relapsing cGVHD in MSD (HR=0.2, 95% CI 0.1-0.4, p<0.001) but not in MUD (HR=0.6, 95% CI 0.4-1.1, p=0.09). This may be related to the use of ATG with Tac/MTX in MUD which was not used in MSD. HCT-CI ≥3 was the only other significant predictor of cGvHD (HR=0.6, 0.4-0.9, p=0.03). PFS was similar in PTCy/Tac ± MMF vs Tac/MTX in MSD (univariate HR: 0.8, 95% CI 0.5-1.3, p=0.3) or MUD (univariate HR: 0.8, 95% CI 0.5-1.2, p=0.3). Conclusions: PTCy/Tac ± MMF prophylaxis slows the development of progressive/relapsing cGvHD in MSD vs (Tac/MTX no ATG), but not in MUD (vs Tac/MTX with ATG). The addition of MMF to PTCy/Tac (vs PTCy/Tac) has no significant impact on the risk of progressive/relapsing cGVHD in MSD or MUD; but is associated with a higher risk of de novo cGvHD in MSD and MUD. Our data suggest that multi-center studies are warranted to determine whether MMF should be excluded from cGvHD prevention regimens in the HLA-matched donor setting with PTCy- based GvHD prophylaxis.

Alloantibody Levels, Immunoglobulin Degradation Products, and Platelet Transfusion Response over Successful Desensitization of Severe Alloimmune Platelet Refractoriness with a Novel IgG-Targeted Enzyme Therapeutic

INTRODUCTION Alloimmune platelet refractoriness (APR), an insufficient response to platelet transfusion due to anti-HLA alloantibodies, affects ~25% of acute myeloid leukemia (AML) patients. In APR, HLA- or crossmatch-compatible platelet units may not be identifiable, precluding transfusion and increasing hemorrhage risk. Single antigen bead testing (SAB) semi-quantitates antibody levels against cognate HLA antigens in units of mean fluorescence intensity (MFI). MFI >3,000 suggests an incompatible platelet antigen for transfusion. Imlifidase, an IgG-specific cysteine protease, cleaves IgG first into single-cleaved IgG (scIgG) with limited Fc-mediated function, then into inactive F(ab') fragments 1. We previously reported successful desensitization and provision of permissive platelet transfusions in an APR patient following desensitization treatment with imlifidase. Here we report pre- and post-desensitization alloantibody (PDAb) levels in correlation with IgG degradation products and response to single donor platelet transfusion. CASE As described previously 2, a 43-year-old highly sensitized (calculated PRA [cPRA] 99.9%) woman with AML and history of life-threatening thrombocytopenic hemorrhage secondary to APR presented for matched-unrelated donor stem cell transplantation. Nationwide, few compatible platelet units were identified to support her through the anticipated platelet nadir. Following conventional desensitization, cPRA did not change significantly. Following imlifidase-desensitization [0.25 mg/kg IV (D-1 and D1)], cPRA decreased significantly. 7 single-donor, antigen-avoidance platelet units produced corrected count increments (CCI) [median (interquartile range) of 6,000 (500-7500)]. The patient experienced no hemorrhage and was discharged stable, post-platelet engraftment on D+19. METHODS With IRB approval, patient data and samples (D-16; D-1 post-conventional desensitization with rituximab and therapeutic plasma exchange; D0 post-imlifidase dose 1; D2 post-imlifidase dose 2; and D7, D14 and D29 follow-up samples) were collected. Serial dilutions of patient D-1 serum were tested with SAB (LABScreen single antigen, One Lambda/ThermoFisher, West Hills, California). SDS-PAGE (gradient gel, non-reduced conditions), Western Blot (antiF(ab') detection), and SAB were performed and acceptable antigens (to molecular specificity, targeted by MFI ≤3,000) were compared over the clinical course. Summative MFIs targeting transfused single donor platelet units were compared with 1-hour CCI. Wilcoxon matched-pairs signed rank for matched, nonparametric values and Chi-squared or Fisher's exact for categorical variables were used. P <0.05 was significant. RESULTS/DISCUSSION The D-1 sample (post-conventional desensitization, pre-imlifidase) showed exquisite HLA sensitization. The highest Class A and B antibodies demonstrated an effective MFI of >4,000,000, each (Fig. A). PDAb and the number of unacceptable antigens decreased significantly in D0 (post-imlifidase) vs. D-1 (pre-imlifidase) samples; Intact IgG and scIgG were eliminated from the D0 and D2 samples (Fig. B). Of 7 single donor platelet transfusions, the 5 producing adequate response were each targeted by a summative MFI ≤4,000 (median 4,000 MFI, range 300-4,000). The 2 units producing inadequate CCI response were targeted by summative MFI >4,000 (5,050, 4,900-5,200), suggesting a threshold summative MFI precluding adequate response. CONCLUSIONS Here we show that the patient's pre-desensitization alloantibody levels significantly exceeded the analytical range of the SAB; PDAb levels declined significantly from baseline, correlating with lack of intact IgG and scIgG following imlifidase; and permissive transfusions (CCI >5,000) were seen to platelets targeted by ≤4,000 summative MFI. These results suggest imlifidase is capable of effective desensitization despite profound baseline sensitization, with rapid cleavage of intact IgG to F(ab'), resulting in the temporary reduction of unacceptable antigens. Larger scale investigation of imlifidase in desensitization of APR patients requiring significant transfusion over a limited period of time, along with investigation into transfusion strategies in desensitized APR, are warranted. REFERENCES Am J Transpl. 2022;22(3):691-697.Blood. 2022;140 (Suppl. 1):8562-3. .

Single-Cell Analyses Unveil a Potential Mechanism Promoting Graft-Versus-Leukemia Response in Haploidentical Transplantation Using Peripheral Stem Cells Plus Cord Blood Grafts through Early Immune Reconstruction of CD8+ Infg+ T Cells

Abstract Background Haploidentical donor stem cell transplantation (haplo-SCT) by using G-CSF-primed peripheral stem cells combined with bone marrow grafts (PBSC+BM) represents a widely employed strategy for acute myeloid leukemia (AML). While leukemic relapse is one of the main reasons for the failure of SCT. Surprisingly, our clinical data found that haploidentical peripheral stem cells combined with cord blood (haplo-PBSC+cord) transplantation had significantly lower incidence of relapse than haplo-PBSC+BM transplantation. Nonetheless, the underlying mechanism needs to be explored. Method From 2021 to 2022, bone marrow samples at 1 and 3 months post-transplantation from 4 AML patients who underwent haplo-PBSC+cord transplantation and 3 AML patients who received haplo-PBSC+BM transplantation were obtained. We used single-cell RNA-sequence (scRNA-seq) technology for analysis of hematopoietic reconstitution disparity between the PBSC+cord and PBSC+BM groups. Results Significant disparities manifest in the initial stages of hematopoietic reconstitution between the PBSC+cord and the PBSC+BM groups. Notably, at 1 month and 3 months post-transplantation, the PBSC+cord group demonstrated conspicuous reconstitution of lymphoid and erythroid cells, with CD8+ T cells exhibiting the most pronounced effect. Differential gene analysis revealed that T cells in the PBSC+cord group display elevated expression of graft-versus-leukemia (GVL)-related cytokines, including IFN-γ, CCL3, and IL1B, when compared to the PBSC+BM group. Furthermore, noteworthy differences in T cell subsets were observed between the two groups. Within 1 month and 3 months post-transplantation, the PBSC+cord group experienced up-regulation of CD8+ effector memory T cells (TEM), characterized by heightened expression of the IFNG gene. Gene Set Variation Analysis (GSVA) unveiled significant enrichment of CD8+ IFNG+ TEM in T cell activation, cytotoxicity, cytokine secretion, and other pathways, suggesting its potential GVL effect. On the contrary, the PBSC+BM group demonstrated a higher proportion of CD4+ T cells, γδT cells, and MAIT cells at 1 month and 3 months post-transplantation. Among CD8+ T cells, the PBSC+BM group showcased a more robust reconstruction of CD8+ TIGIT+ T cell subsets, which highly express exhaustion-related genes like TIGIT, LAG3, PDCD1 (PD-1), HAVCR2 (TIM-3), and exhibited increased apoptosis-related pathway activity. Conclusion Our investigation identified a potential mechanism promoting GVL response in the immune reconstitution of haplo-PBSC+cord transplantation.