Cord Blood Transplantation Research Articles

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

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

The HLA-B Leader MM Genotype Has a Negative Impact on Outcomes in HLA-B One Antigen Mismatched and HLA-B Matched Cord Blood Transplantation without Anti-Thymocyte Globulin: Analysis of the Japanese Society for Transplantation and Cellular Therapy

Background: The dimorphism at position -21 of exon 1 in HLA-B gives rise to leader peptides featuring either methionine (M) or threonine (T) as the second residue in the processed leader peptide (HLA-B leader). The cell surface abundance of HLA-E is positively correlated with the copy number of −21M HLA-B. In hematopoietic cell transplantation (HCT), the MM genotype in the recipients is associated with worse outcomes after HLA-matched and mismatched unrelated bone marrow and peripheral blood stem cell transplantation compared with TT (Kanaya M, et al. ASH Annual Meeting 2021, Petersdorf EW et al. Lancet Haematol. 2020 and Blood. 2020). Eurocord/EBMT study revealed HLA-B leader mismatch in HLA-B mismatched combination is associated with relapse and non-relapse mortality (NRM) risks after cord blood transplantation (CBT) (Petersdorf EW et al. Haematologica 2021). Notably, approximately 70% of patients in the literature administrated anti-thymocyte globulin (ATG) for graft-versus-host disease (GVHD) prophylaxis. The impacts of HLA-B leader dimorphism on the outcomes of CBT still needed to be elucidated more. Particularly, we were interested in the significance of HLA-B leaders in CBT without an ATG, then we conducted a retrospective study to elucidate it. Methods: Clinical data of 10,569 patients who underwent single-unit CBT for acute myeloid leukemia (AML, n=5,518), myelodysplastic syndrome (MDS, n=1,483), acute lymphoblastic leukemia (ALL, n=2,020), and lymphoma (n=1,548) between 2008 - 2021 were provided by the Japanese Data Center for Hematopoietic Cell Transplantation. HLA-A, -B, -C, and -DRB1 typing was performed at least at the antigen level. The leader genotype is defined based on the two HLA-B allotypes. All patients were not used ATG for GVHD prophylaxis. Study outcomes were overall survival (OS), cumulative incidences of relapse, NRM, and grade II-IV acute GVHD (aGVHD). Multivariable Cox regression analysis including covariables; disease risk index (DRI), myeloablative/reduced-intensity conditioning, presence of total body irradiation as a conditioning regimen, short-term methotrexate or mycophenolate mofetil for GVHD prophylaxis, recipient cytomegalovirus serostatus. All statistical analyses were performed with EZR. Results: The median patient's age was 53 (range 0-88) years. The numbers of patients with HLA-B leader TT, MT, and MM genotype were 7,639 (72.3 %), 2,707 (25.6 %), and 223 (2.1 %), respectively. To classify HLA-B match/mismatch status, we stratify “HLA-B one locus mismatched (GVH direction)” and HLA-B matched (no GVH direction mismatch)“. First, we focused on HLA-B one antigen mismatched (HLA 5/6 antigen matched, n = 1172) setting as shown in the previous literature. Recipient MM genotype showed significantly worse OS and relapse in the multivariate analysis compared to MT or TT genotype (Tx) (Figure) (OS: hazard ratio [HR] 0.543 [95% CI, 0.311 - 0.947]; p = 0.032, relapse: [HR] 2.863 [95% CI, 1.330 - 6.165]; p = 0.007). Recipient MM didn't relate to relapse and grade II-IV aGVHD. Next, we explored the impacts of HLA-B leaders in HLA-B antigen-matched CBT (3/6 - 6/6 matched, n = 3995). Donor MM genotype demonstrated a negative impact for OS and NRM, not relapse and aGVHD, compared to Tx donor (Figure) (OS: [HR] 0.738 [95% CI, 0.542 - 1.000]; p 0.050, NRM: [HR] 1.695 [95% CI, 1.097 - 2.621]; p = 0.018). Especially, OS and NRM of donor MM genotype were significantly inferior to Tx in HLA 6/6 matched (n = 914) CBT (OS: [HR] 0.311 [95% CI, 0.187 - 0.518]; p < 0.001, NRM: [HR] 3.216 [95% CI, 1.931 - 5.356]; p = 0.034). Conclusions: ATG would affect immune dynamics strongly in CBT via in-vivo T cell depletion, yet the current study demonstrated the HLA-B leader was still a significant risk factor in CBT without ATG for the first time. Recipient MM genotype in HLA-B one locus mismatched (HLA 5/6 matched) and donor MM genotype in HLA-B matched were the risk factors for worse CBT outcomes. We concluded MM genotype donors would be avoided to decrease NRM in HLA-B matched CBT. The precise mechanism of negative impact in CBT outcomes in patients or donor MM genotype remains to be clarified, however, we assume higher level HLA-E expression may be crucial in terms of NKG2A inhibitory signaling to T cells/NK cells and T-cell direct recognition for peptide/HLA-E complex in CBT.

Impact of Conditioning Intensity and Regimen on Outcomes after Unrelated Cord Blood Transplantation for Patients with Myelodysplastic Syndrome

Introduction Allogeneic hematopoietic stem cell transplantation (allo-HSCT) provides curative outcomes in patients with myelodysplastic syndromes (MDS). Unrelated cord blood transplantation (CBT) is an alternative donor option in MDS patients who lack an HLA-matched donor, and the increased availability of CBT expand indications for allo-HSCT in MDS patients. Because concerns have been expressed regarding decreased hematopoietic recovery and increased relapse after CBT, many studies have been conducted to develop the conditioning regimen in CBT. The optimal intensity of conditioning regimen needs to be addressed based on patient- and disease-related factors. However, the optimal intensity of conditioning regimen in CBT for MDS remains unclear. We here conducted a nationwide retrospective study to clarify the optimal conditioning intensity for MDS in CBT. Methods This study included patients diagnosed with de novo MDS according to the WHO classification. The clinical data of 856 de novo MDS patients (i) who were 16-69 years old and (ii) who underwent their initial single-unit CBT between 2001 and 2020 were collected from the Japanese Data Center for Hematopoietic Cell Transplantation. Cox proportional hazards regression models were used to evaluate variables potentially affecting overall survival (OS), chronic graft-versus-host disease (GVHD)- and relapse-free survival (CRFS), and GVHD- and relapse-free survival (GRFS). Fine and Gray proportional hazards models were used to evaluate variables potentially affecting cumulative incidences of relapse (CIR) and non-relapse mortality (NRM), using cumulative incidence curves to accommodate competing events. Results In this study, 501 and 355 patients received myeloablative conditioning (MAC) and reduced-intensity conditioning (RIC), respectively. The median age at CBT was 53 (range,17-69) and 62 years (range,18-69) in MAC and RIC groups, respectively. The most frequently used MAC regimen consisted of total body irradiation >8 Gy-based regimen (n=209, 41.7%), followed by fludarabine (Flu) with myeloablative doses of busulfan (Bu 9.6 to 12.8 mg/kg)-based regimen (n=93, 18.6%). The most frequently used RIC regimen consisted of Flu with reduced doses (80 to 120 mg/m 2) of melphalan-based regimen (n=245, 96.1%), followed by Flu with reduced doses of Bu (6.4 mg/kg)-based regimen (n=63, 17.7%). The 3-year OS were 44.3 % and 48.8 % in MAC and RIC groups, respectively; the 3-year CRFS were 33.8 and 37.2%; the 3-year GRFS were 19.2 % and 26.9%; the 3-year CIR were 27.1% and 30.0%; and the 3-year NRM were 18.6% and 18.2 %. The univariate analysis revealed that RIC group tended to correlate with higher GRFS than MAC group (Hazard ratio (HR) 0.86 [95% confidential interval 0.74-1.00]; P=0.057), but there was no significant difference of OS (HR 0.95 [0.79-1.13]; P=0.552), CRFS (HR 0.95 [0.80-1.12]; P=0.522), CIR (HR 1.11 [0.87-1.41]; P=0.401) and NRM (HR 0.96 [0.77-1.20]; P=0.735) between MAC and RIC groups. The multivariate analyses confirmed the better GRFS in RIC group than MAC group (HR, 0.73 [0.61-0.89]; P=0.001). Apart from the conditioning intensity, the following six factors were associated with worse overall mortality: patient's age (40-60 years; P=0.039 and >60 years; P<0.001), patient's sex (male; P=0.038), performance status (PS) at CBT (PS 2-4; P=0.033), hematopoietic cell transplantation-specific comorbidity index (HCT-CI) (HCT-CI ≥3; P=0.035), high number of platelet transfusion before HSCT (≥20 times; P<0.001) , and cytogenetic risk group (poor risk; P=0.001). We next performed the subgroup analysis stratified by the patient's characteristic affecting OS, such as age, sex, PS, HCT-CI, the number of platelet transfusion, and cytogenetic risks. The subgroup analysis showed the better OS (HR, 0.74 [0.59-0.92]; P<0.007), CRFS (HR 0.74, [0.60-0.94]; P=0.012), and GRFS (HR 0.62, [0.50-0.78]; P<0.001) of RIC group than MAC group among patients with patients aged >60 years, but no significant impact on CIR and NRM. Conclusion This study showed no significant difference of OS, CRFS, CIR and NRM between MAC and RIC groups, but RIC group correlated with better GRFS in the entire population. Furthermore, the subgroup analysis showed that RIC regimen may be preferable for patient aged >60 years. These findings would improve the management for CBT candidates with MDS.

Outcomes and Prognostic Factors of Second Allogeneic Hematopoietic Cell Transplantation in Patients with Acute Lymphoblastic Leukemia: A Study from the Adult Acute Lymphoblastic Leukemia Working Group of the Japanese Society for Transplantation and Cellular Therapy

Background Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative treatment option frequently used in patients with acute lymphoblastic leukemia (ALL). However, relapse after allo-HCT remains the main concern because it is associated with poor outcomes, with a long-term survival rate < 10 %. There is no standard treatment for patients with ALL who relapsed after allo-HCT. Second allo-HCT (allo-HCT2) is a curative treatment option for patients with ALL who relapsed after the first allo-HCT (allo-HCT1). However, data on allo-HCT2 in patients with ALL are limited, and the indications and outcomes of allo-HCT2 are unclear. Therefore, this study aimed to investigate the outcomes and prognostic factors of patients who underwent allo-HCT2 after ALL relapse. Methods This study included 425 adult patients with ALL who underwent allo-HCT2 after relapse between January 2001 and December 2020. The primary endpoint was 2-year overall survival (OS), which was evaluated using the log-rank test. Prognostic factors for the primary endpoint were evaluated using the multivariable Cox proportional hazards model. The variables considered in the Cox proportional hazards model are listed in the Table. The impacts of the candidate factors are shown as hazard ratios (HRs) and 95% confidence intervals (CIs). Additionally, we performed an analysis stratified by disease and disease status because Philadelphia chromosome (Ph)-positive B-ALL could affect the treatment and disease status at allo-HCT2 and the outcome. Results The median age at allo-HCT2 was 36 years (interquartile range; 27-48 years) and 220 patients (52%) were male. According to the Eastern Cooperative Oncology Group, 94 patients (22%) had a performance status of > 2. There were 235 patients (55%) with Ph-negative B-ALL, 122 patients (29%) with Ph-positive B-ALL, and 68 patients (16%) with T-ALL. Regarding disease status at allo-HCT2, 217 patients (51%) had any complete response (CR). One hundred forty-eight patients (35%) received myeloablative conditioning regimen. Ninety patients (21%) received related bone marrow (BM) or peripheral blood (PB) transplantation, 137 patients (32%) received unrelated BM or PB transplantation, and 198 patients (47%) received unrelated cord blood (CB) transplantation. The median observation time of survivor after allo-HCT2 was 22.3 (interquartile range; 6.3-82.5) months and 2-year OS was 28.0% (95% CI, 23.7-32.4). After stratified disease and disease status, the 2-year OS was 56.5% (95% CI, 44.6-66.8), 31.7% (95% CI, 24.0-39.7), 21.5% (95% CI, 10.6-34.9), and 13.1% (95% CI, 8.4-18.8) in any CR (Ph-positive B-ALL), any CR (other), active disease (Ph-positive B-ALL), and active disease (other), respectively ( P < 0.001) (Figure). In multivariable analysis, Ph-positive B-ALL (HR, 0.48; 95% CI, 0.36-0.65; P < 0.001), tacrolimus-based GVHD prophylaxis at allo-HCT2 (HR, 0.72; 95% CI, 0.54-0.95; P = 0.022) were identified as significantly positive prognostic factors for 2-year OS, while allo-HCT1 to allo-HCT2 < 12 months (HR, 1.38; 95% CI, 1.02-1.88; P = 0.038), relapse within 12 months after allo-HCT1 (HR, 1.37; 95% CI, 1.01-1.85; P = 0.043), ECOG PS > 2 (HR, 1.89; 95% CI, 1.44-2.49; P < 0.001), active disease at allo-HCT2 (HR, 1.88; 95% CI, 1.46-2.42; P < 0.001), unrelated BM or PB transplantation at allo-HCT2 (HR, 1.78; 95% CI, 1.22-2.59; P = 0.003), and CB transplantation at allo-HCT2 (HR, 1.54; 95% CI, 1.09-2.18; P = 0.013) were identified as significantly negative prognostic factors for 2-year OS. Conclusion In this study, we demonstrate that the 2-year OS was 28.0% in patients with ALL who underwent allo-HCT2 and identified the prognostic factors that may guide patients to benefit from allo-HCT2.

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

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

Higher CD34+ Cell Doses Correlate with Reduced Incidence of Relapse and Better Event-Free Survival after KIR-Ligand Mismatch Cord Blood Transplantation for Childhood Acute Myeloid Leukemia

Introduction In children with acute myeloid leukemia (AML), hematopoietic stem cell transplantation (HSCT) is an important treatment, and cord blood units from unrelated donors provide a well-established source of stem cells for HSCT. The main advantages of using cord blood include rapid availability, allowance of greater HLA disparities due to a relatively low risk of severe graft-versus-host disease (GVHD), and possibly a greater graft-versus-leukemia (GVL) effect. Killer cell immunoglobulin-like receptors (KIRs) are the main receptors on natural killer cells that play an important role in GVL after HSCT. Previous studies on the effects of KIR-ligand (KIR-L) incompatibility in unrelated cord blood transplantation (CBT) for leukemia have resulted in conflicting results, and in some studies, this has led to an increased incidence of acute GVHD. Furthermore, the impact of KIR-L mismatch on outcomes in children with AML remains poorly understood. In this study, we explored the association of KIR-L incompatibility and other clinical factors with patient outcomes in children with AML who received CBT. Methods Data were collected from the Transplant Registry Unified Management Program sponsored by the Japanese Society for Transplantation and Cellular Therapy and the Japanese Data Center for Hematopoietic Cell Transplantation. The patients were selected according to the following criteria: (1) de novo non-M3 AML, (2) age < 16 years and CR1 or CR2 at the time of receiving HSCT, (3) no prior HSCT, and (4) HSCT performed between 2000 and 2021. Patients without information on survival and disease recurrence or those with Down syndrome were excluded. KIR-L mismatch in the graft-versus-host direction was defined as lacking a donor KIR-L group (HLA-C1, C2, Bw4, or A3/A11) in a recipient. A myeloablative conditioning regimen was defined as total-body irradiation (TBI) at > 8 Gy, melphalan at > 140 mg/m 2, or busulfan at ≥ 9 mg/kg. All other regimens were analyzed as reduced-intensity conditioning regimens. Adverse cytogenetics were defined as previously described [Creutzig et al. Blood, 2012]. Results A total of 299 patients were included. The median age at HSCT was 5 years (range, 0-15), and the median follow-up period for survivors was 7.2 years (range, 0.1-22.4). The median total nucleated cell and CD34+ cell doses were 6.7 x 10 7/kg (range 0.01-12.3) and 1.9 x 10 5/kg (range 0.01-59.4), respectively. The study cohort consisted of 240 patients in the KIR-L match group and 59 patients in the KIR-L mismatch group. The background characteristics of these two groups did not differ significantly, except for a trend indicating that the KIR-L mismatch group received CBT more recently ( p = 0.063). The cumulative incidence rates of neutrophil recovery at Day 42 were 93.3% (95% CI, 89.3-95.9%) and 91.5% (95% CI, 80.0-96.5%) ( p = 0.980), and the cumulative incidence rates of platelet engraftment at 6 months were 91.5% (95% CI, 87.1-94.5%) and 89.8% (95% CI, 77.9-95.5%) ( p = 0.314) for the KIR-L match and mismatch groups, respectively. The cumulative incidence rates of grade II-IV acute GVHD at Day 100 were 40.9% (95% CI, 34.6-47.1%) and 40.7% (95% CI, 28.0-52.9%) ( p = 0.709), whereas those of chronic GVHD at one year after transplantation were 15.6% (95% CI, 11.2-20.6%) and 15.9% (95% CI, 7.8-26.6%) ( p = 0.914) for the KIR-L match and mismatch groups, respectively. In univariate analyses, the 5-year event-free survival (EFS) was 70.1% (95% CI, 63.6-75.6%) for the KIR-L match group and 72.9% (95% CI, 59.0-82.8%) for the KIR-L mismatch group ( p = 0.609). Stratification by CD34+ cell doses showed a significant correlation between higher CD34+ cell doses and better EFS in the KIR-L mismatch group (Figure 1), attributed not only to reduced nonrelapse mortality but also to a lower incidence of relapse. In multivariate analysis of EFS, KIR-L mismatch with high CD34+ cell doses (> the median doses) was identified as an independent favorable prognostic factor (Table 1; hazard ratio = 0.21, p = 0.037). Conclusion Our study demonstrates that higher CD34+ cell doses were associated with a lower relapse rate and better EFS in KIR-L mismatch CBT for childhood AML. This finding is noteworthy, as previous literature has primarily emphasized the role of higher CD34+ cell doses in reducing nonrelapse mortality. Our results suggest that higher CD34+ cell doses are also crucial for achieving a high GVL effect in the context of KIR-L mismatch CBT.

Infusion of UM171-Expanded Cord Blood Led to Excellent Survival in Patients with High-Risk Leukemias: Results from Two Independent Phase II Studies

Background: Cord blood transplant (CBT) recipients experience delayed hematopoietic recovery and an increased risk of non-relapse mortality (NRM). UM171 is a small molecule that expands hematopoietic stem and progenitor cells (HSPC). An initial phase I-II clinical trial of a single UM171-expanded CBT was associated with low NRM and excellent long-term outcomes. (S Cohen et al. Lancet Haematology 2020). With the primary goal of generating increased numbers of HSPC to supplement a conventional single cord blood (CB) graft, we tested the same approach exclusively in high and very high-risk patients with acute leukemias/myelodysplastic syndromes (MDS). Methods: Between 2019 and 2022, two single independent prospective phase II studies were conducted in Montreal, at the Maisonneuve Rosemont Hospital and in Seattle, at the Fred Hutchinson Cancer Center. Primary objectives were safety/NRM and progression free survival at 2-years post-transplant. Only patients with high and very-high risk acute myeloid leukemia (AML), acute lymphoid leukemia (ALL) and MDS were eligible. Patients were required to have adequate organ function and comorbidity index as defined by the transplant center. Patients received a single UM171 7-day expanded and cryopreserved CB after either a myeloablative or mid-intensity conditioning regimen. All patients received tacrolimus and mycophenolate mofetil for GVHD prophylaxis. Results: A total of 52 patients were enrolled (31 in Montreal and 21 in Seattle) with 2 patients not receiving the UM171 expanded product and therefore removed from the final analysis. Patient's characteristics are shown in Table 1. The median age was 44 years (range 19-66) and weight 78 kg (range, 44-145). Twenty-eight patients (54%) were either in a no complete response (CR) status or in ≥CR2, ten (19%) were p53+ and 17 (33%) were second or third transplants. Forty patients (77%) received a 5/8 HLA-matched CB unit and the median of CD34+ cells infused was 4.7 10 6/Kg (0.9-7.5). All patients engrafted (ANC >500 10^ 9/L for 2 consecutive days) at a median of 17 days (range, 9-39 days). The median time to platelet recovery (>20 x 10^ 9/L) was 37 days (range 24-116). With a median follow-up of 24 months (range 0.7 - 39), the probability of 2-year overall survival (OS) and progression-free survival (PFS) was 67% (95% CI, 54-82) and 63% (95% CI, 50-79). OS for second/third transplants and p53+ patients was 64% (95% CI, 43-96) and 40 (95% CI, 19-86), PFS was 51 % (95% CI, 29-87) and 40 (95% CI, 19-86), respectively. At 2 years, the cumulative incidence of NRM was 19% (95% CI, 8-31) while the incidence of relapse was 18% (95% CI, 6-29). The incidence of grade II-IV and III-IV acute GVHD was 69% (95% CI, 56−82%) and 16% (95% CI, 6−27%). The rate of moderate/severe chronic GVHD was 7% (95% CI,1−15%) and translated in an incidence of a chronic-relapse-free-survival of 55% (95% CI, 42−72%). Of note, Kaplan-Meier analysis of all clinical outcomes showed no difference for patients treated in Montreal and Seattle, and results were similar for both centers (Figure 1). Conclusions: The results of 2 independent Phase II clinical studies demonstrated that infusion of a UM171 single CBT led to excellent clinical outcomes in patients with high and very-high risk malignancies including patients with p53+ mutation. We also observed encouraging results for patients undergoing second/third transplants (33% of the entire cohort). Clinical outcomes were similar between the two Transplant Centers. Based on these positive results, a multicenter randomized clinical trial is currently in the planning stage.

Single CBT As 2nd Allo-SCT Is Promising for Selected Patients with Relapsed Hematopoietic Malignancies

Background: Hematopoietic malignancies that relapse after allogeneic stem cell transplantation (allo-SCT) generally have a poor prognosis, and there is no standard treatment. Second allo-SCT is a potentially curative treatment, but many patients do not receive 2nd allo-SCT at the best time because of the long preparation time for transplantation, and even if they do, treatment-related complications and relapse of the underlying disease often lead them to fatal outcomes. Umbilical cord blood is considered to be a promising source of 2nd allo-SCT because of its short preparation time, rapid and high graft-versus Leukemia (GVL) effect after transplantation, and better response to GVHD treatment compared to other donor sources. Therefore, we investigated the usefulness of cord blood transplantation for relapsed hematopoietic malignancies after allo-SCT. Methods: We retrospectively analyzed the outcomes of patients with hematopoietic malignancies who received single cord blood transplantation (CBT) as 2nd allo-SCT for relapse after allo-SCT in Toranomon Hospital between Apr. 1999 and Mar. 2022. We exclude the patients with Eastern Cooperative Oncology Group (ECOG) performance status(PS) of 4. Results: 263 patients were included in this study. There were 179 patients with myeloid neoplasms and 84 with lymphoid neoplasms. Median age was 45 years (range: 18-71). 239 patients were in non-remission and 24 in remission before SCT. Median interval between 1st SCT and 2nd SCT was 293 days (26-4703). Donor sources of 1st allo-SCT were related donor in 80, unrelated donor in 62, and sCBT in 121 patients. 135 patients received myeloablative conditioning for 2nd allo-SCT, and 128 patients underwent reduced intensity-conditioning. About cord blood as the donor source of 2nd allo-SCT, the median total nucleated cell count at cryopreservation was 2.71(×10 7)/kg (1.67-5.85), and median CD34 + cell count at cryopreservation was 0.97(×10 5)/kg (0.25-3.18). Median observation period of survivors was 1726 (122-6286) days after 2nd allo-SCT. Overall survival (OS), non-relapse mortality and relapse at 2-year were 16.7%, 46.9% and 40.6%, respectively. Younger patients (< 50 years) had significantly better OS than older patients (50 years and more), with 2-year OS of 21.5% and 9.9%, respectively (P < 0.001). Patients with good PS (0 and 1) had significantly better survival than those with poor PS(2 and 3), with 2-year OS of 23.4% and 2.4%, respectively (P<0.001). Patients with myeloid malignancies tended to have better survival than those with lymphoid malignancies, with 2-year survival rates of 19.2% and 11.9%, respectively (P=0.341). Patients with longer interval between SCTs (>1 year) had significantly better survival than those with shorter interval (<1 year), with 2-year OS of 23.6% and 11.6%, respectively (P=0.00443). In multivariate analysis, younger age (<50), good PS (0-1), long interval between SCTs(≧1 year) showed a superior OS. In the younger age population, patients with myeloid neoplasms showed a superior OS compared to those with lymphoid neoplasms (2yrOS: 30.3% vs 10.6%, P=0.00318). Furthermore, patients with myeloid neoplasms having good PS and long interval between SCTs showed an extremely high survival rate of 50.5% at 2 years (n=31)(Figure 1). In the elderly population, patients with long interval and good PS showed a relatively good OS of 31.4% at 2 years (n=28)(Figure 2). The type of disease (myeloid vs lymphoid) didn't have a significant influence on OS in this subpopulation (28.1% vs 50.0%, P=0.129). Conclusion: Although the outcomes of CBT as 2nd allo-SCT haven't been satisfactory, there are certain populations, including elderly patients, with favorable OS.

Multiple-Factor Analysis of Human Herpes Virus 6 Infection in Complementary Transplantation with Haploidentical Stem Cells and Unrelated Cord Blood

Background: Hematopoietic stem cell transplantation (HSCT) can ultimately cure various hematological disorders. Building upon the basis of post-transplant cyclophosphamide (PT-cy) haploidentical HSCT, we innovatively employed a combination of haploidentical related donors and unrelated cord blood donors for complementary transplantation to treat pediatric leukemia and severe thalassemia. This approach has been successful, and complementary transplantation has become an important option in haploidentical HSCT. However, with the development of haploidentical HSCT and the long-term use of immunosuppressive agents, viral infections have gained increasing attention, and human herpesvirus 6 (HHV-6) is one of the concerning viruses. HHV-6 exists in two variants, HHV-6A and HHV-6B, with HHV-6B being the common infection in HSCT. HHV-6B is characterized by a preference for lymphocytes and neurons and can easily reactivate in patients with compromised immune systems after HSCT, leading to severe and irreversible brain and nerve damage, and in severe cases, death. In this study, we aim to identify the susceptible factors for HHV-6B infection in cases of complementary transplantation, with the goal of improving the safety of complementary transplantation in HSCT. Objective: Through a retrospective analysis, we aim to identify the factors associated with HHV-6 infection after complementary transplantation in HSCT, providing clinical evidence for prevention, diagnosis, and treatment. Methods: We selected cases of HSCT using complementary transplantation from December 2018 to May 2022. Factors such as the primary disease of the patients, gender, age, donor-recipient blood type, haploidentical donor engraftment, different HLA-matched cord blood engraftment, neutrophil and platelet engraftment times, use of ATG and glucocorticoids, fever condition, timing of HHV-6 infection, and the time to seronegativity after treatment were analyzed to identify the characteristics and related risk factors of HHV-6B infection. Results: Among 142 cases (73 with thalassemia, 19 with AML, 37 with JMML, 2 with Fanconi anemia, 8 with SAA, and 8 with ALL) using complementary transplantation, 91 cases were infected with HHV-6, resulting in an infection rate of 64%. In the infection group, 8 patients were under the age of 2 years (8.8%), while 83 patients were 2 years or older (91.2%). In the uninfected group, 17 patients were under 2 years of age (33.3%), and 34 patients were 2 years or older (66.7%). (p<0.001). Regarding the type of graft, 79 patients in the infection group received cord blood transplantation (86.8%), and 12 patients received peripheral blood transplantation (13.2%). In the uninfected group, 19 patients received cord blood transplantation (37.3%), and 32 patients received peripheral blood transplantation (62.7%). (p<0.05). Regarding ATG use, 61 patients in the infection group received ATG (67%), and 12 patients did not (33%). In the uninfected group, 25 patients received ATG (49%), and 26 patients did not (51%). (p=0.035). In terms of glucocorticoid use, 82 patients in the infection group received glucocorticoids (90.1%), and 9 patients did not (9.9%). In the uninfected group, 13 patients did not receive glucocorticoids (25.5%), and 38 patients did (74.5%). (p<0.05). Regarding neutrophil engraftment time, it was 36 days in the infection group and 23 days in the uninfected group. Regarding platelet engraftment time, it was 43.5 days in the infection group and 18.5 days in the uninfected group. In terms of CMV and EB virus infection, only one patient in the infection group had concurrent CMV infection, and there were no cases of concurrent EB virus infection. Conclusion: In complementary transplantation, cord blood transplantation, glucocorticoid use, ATG use, and recipient age are high-risk factors for HHV-6 infection/reactivation. There were no significant differences in HHV-6 infection between different diseases treated with complementary transplantation. Furthermore, HHV-6 infection significantly delays the engraftment of neutrophils and platelets. Keywords: Hematopoietic stem cell transplantation, haploidentical, cord blood, human herpesvirus 6 (HHV-6)

Selecting the Right Alternative Donor: Comparison of Outcomes of HLA-Mismatched Alternative Donor Hematopoietic Cell Transplantations in Adult Patients with Acute Lymphoblastic Leukemia Regarding KIR-Ligand Mismatch

Background: Allogeneic hematopoietic cell transplantation from cord blood (CBT) or haploidentical donor (HIDT) has proved to be a viable option for patients unable to find a human leukocyte antigen (HLA)-matched conventional donor. However, few single-centered studies have compared outcomes of the two alternative donor transplantations in adult acute lymphoblastic leukemia (ALL). Aim: Our aim is to compare outcomes of adult ALL patients treated with CBT with those treated with HIDT. Secondly, we tried to find out factor that could be considered in selecting donor for alternative donor transplantation to improve clinical outcomes. Methods: We compare outcomes of adult ALL patients treated with CBT (n=134) between 2008 and 2022 with those treated with HIDT (n=47) between 2018 and 2022.Conditioning regimen for CBT consisted of total body irradiation (12Gy) plus cytarabine (9g/m 2) plus fludarabine (150mg/m 2). Graft-versus-host disease (GVHD) prophylaxis was attempted using tacrolimus and mycophenolate mofetil. For HIDT, we used reduced toxicity conditioning (RTC) regimen including fludarabine (150mg/m 2) plus busulfan (6.4mg/kg). GVHD prophylaxis was done with ATG 1.5mg for 4 days plus short course methotrexate (MTX) (15mg/m 2) plus tacrolimus. Killer cell immunoglobulin-like receptor (KIR) ligand mismatch was calculated in both GVH and HVG direction using HLA-KIR ligand database, and its effect on clinical outcomes of alternative donor transplantation was investigated. Results: In HIDT, CD34+ cell count (´10 6/kg) was significantly higher (7.4 vs. 0.1, P<0.001), and the patients were older (49 vs. 33.5, P<0.001) compared to CBT. Other characteristics, such as cytogenetic risk and leukocyte count at diagnosis, did not show significant difference between the two groups. Incidence of acute GVHD II-IV (51.1% vs. 50.0%), III-IV (25.5% vs. 17.9%), and moderate to severe chronic GVHD (10.8% vs. 11.0%) between HIDT vs. CBT were similar. After median follow-up of 39.4 months (range: 5.5-167.4), HIDT showed higher cumulative incidence of relapse (CIR) compared to CBT (47.9% vs. 18.9%, P<0.001), which remained true even after stratifying by age subgroup (Age<40: P=0.033, Age≥40: P=0.002). Conversely, CBT showed higher non-relapse mortality (NRM) than HIDT (22.8% vs. 9.0%, P=0.038), but the same was true only in the older age subgroup (Age<40: P=0.484, Age≥40: P=0.002). These effects summed up to produce comparable results in estimated 3-year disease-free survival (DFS) of CBT and HIDT (58.4% vs. 43.5%, P=0.103), especially in the older subgroup (38.7% vs. 40.7%, P=0.897). Multivariate analysis also revealed that HIDT was related with higher relapse (HR 3.47; 95%CI 1.92-6.27, P<0.001), and CBT with higher NRM (HR 4.18; 95%CI 1.42-12.3, P=0.009). GVH direction KIR ligand mismatching worked for lower 3-year DFS in CBT (40.3% vs. 74.4%, P=0.007), although CIR and NRM did not show significant difference (27.8% vs. 15.6%, P=0.178; 35.0% vs 18.4%, P=0.057, respectively). On the other hand, the mismatch resulted in lower incidence of acute GVHD II-IV (32.0% vs. 54.2%, P=0.011). The trend remained when such effect was investigated separately in CBT and HIDT, but it was not statistically significant (33.3% vs. 53.1%, P=0.082; 28.6% vs. 57.6%, P=0.053, respectively). Conclusions: Our data shows higher NRM in CBT, and unexpected higher relapse rate in HIDT. Age of the patient should be considered when choosing CBT, because in older patients CBT showed notably worse NRM compared to HIDT. Higher incidence of relapse in HIDT may be attributable to ALL disease characteristics itself or insufficient elimination of leukemic cells by RTC regimen with stronger GVHD prophylaxis. Similar to what is known in acute myeloid leukemia, GVH direction KIR incompatibility showed protective effect against acute GVHD in ALL. However, the mismatch resulted in worse DFS in ALL patients treated with CBT, but not in those treated with HIDT. Possible explanation to this phenomenon is that the number of NK cells in cord blood was insufficient for mismatch-induced graft-versus-leukemia effect, while its immune response against infected cells was suppressed by the same mechanism that resulted in lower acute GVHD. Keywords: Acute lymphoblastic leukemia, Cord blood transplantation, Haploidentical donor transplantation, HLA-mismatched transplantation, Killer-cell immunoglobulin like receptor

Excellent Outcome Following Maintenance Therapy with Gilteritinib after Allogeneic Hematopoietic Stem Cell Transplantation for FLT3-Mutated Acute Myeloid Leukemia Even in Non-Remission Status

[Background] FMS-like tyrosine kinase 3 (FLT3) mutation has been shown to be a poor prognostic factor for recurrence and overall survival in AML. In recent years, various FLT3 inhibitors have been successively developed and reported to improve the prognosis of FLT3-mutated AML. However, relapse after allogeneic stem cell transplantation(allo-HSCT) remains high, and strategies to improve prognosis are desired. Clinical trials have been conducted using FLT3 inhibitors as maintenance therapy allo-HSCT to reduce the relapse rate and some efficacy has been reported, but real-world data on maintenance therapy with gilteritinib for FLT3-mutated AML after allo-HSCT are limited, especially after cord blood transplantation (CBT). [Objective and method] To assess the efficacy, safety, clinical features and outcome of gilteritinib maintenance after allo-HSCT for FLT3-mutated AML, we retrospectively analyzed patients underwent allo-HSCT, most of which are CBT for FLT3-mutated AML from April 2019 to October 2022. [Result] During the study period, 46 patients received allo-HSCT for FLT3-mutated AML in our institute. The median follow-up day of survivors was 649 (115-1149). The median age of the patients was 55 years (range, 20-75). Twenty-seven patients had de novo AML, 16 had AML with myelodysplasia related changes, and 3 had therapy related AML. One had favorable karyotype, 37 had intermediate, and 6 had adverse. Thirty-six patients received myeloablative pretransplant conditionings (MAC), and 10 received reduced intensity conditionings (RIC). All but 9 were in in non-remission at HSCT. The majority, 40, had used unrelated cord blood, 3 did unrelated bone marrow, 2 did unrelated peripheral blood, and 1 did related peripheral blood as grafts. Twenty-eight patients received gilteritinib maintenance therapy after HSCT, whereas 18 did not. Between the 2 groups, the patient characteristics, AML status, and HSCT procedures were well balanced. At 2 years after HSCT, overall survival (OS), disease free survival (DFS), relapse rate (RR), and non-relapse mortality (NRM) of whole studied population were 65.0%, 56.3%, 27.0%, and 21.1%, respectively. Patients with gilteritinib maintenance showed significantly superior OS and DFS to those without gilteritinib maintenance (2-year OS; 84.2% vs 35.7%, P = 0.0030, 2-year DFS; 71.4% vs 30.4%, P = 0.0036)(Figure 1A, 1B). RR and NRM tended to be lower in patients with gilteritinib maintenance than those without (2-year RR; 41.4% vs 18.1%, P = 0.1350, 2-year NRM; 34.4% vs 11.9%, P = 0.0548). Even if in non-remission status at HSCT, 23 patients with gilteritinib maintenance showed excellent outcome with 2-year OS 81.6%, DFS 70.9%, RR 21.2%, and NRM13.9%. A subanalysis of the four groups by with or without gilteritinib maintenance and by pretreatment conditioning intensity showed that patients who received MAC and gilteritinib maintenance had the most superior 2-year OS 94.1%. [Conclusion] Our data indicated that following maintenance therapy with gilteritinib after allo-HSCT could overcome the poor prognosis of FLT3-mutated AML even for those in non-remission status, despite the profound chemo-resistant character of FLT3-mutated AML.

Effect of Differences in Immunological Reconstitution By Donor Age and Recipient Age on the Incidence of Chronic Graft-Versus-Host Disease

Background: Development of chronic graft-versus-host disease (cGVHD) has been reported to be associated with donor age and recipient age. We hypothesized that differences in post-transplantation immunological reconstitution depending on donor age and recipient age might be responsible for the incidence of cGVHD. Redevelopment of regulatory T (Treg) cell expansion and cytokine production was investigated over time according to donor age and recipient age at the time of transplantation after allogeneic hematopoietic cell transplantation (HCT). Methods: The subjects were 39 consecutive patients who underwent HCT for different hematologic diseases at our hospital between December 2008 and December 2021 and survived for more than 3 years after HCT without cGVHD. The patients were classified into younger (age ≤59, n=23) and older (age ≥60, n=16) groups. The donor source was divided into subgroups based on use of cord blood or an adult donor: cord blood (younger, n=5; older, n=8) and adult donor (younger, n=18; older, n=8). Peripheral blood was drawn from all patients on day 200 and at 24 and 36 months after HCT. Analysis of Treg, T, B, and NK cells was performed using flow cytometry. T cells were isolated using EasySep kits and cultured at 37℃ in 5% CO 2 in air for 4 days with 10% heat-inactivated fetal calf serum as controls, interleukin-2 (IL-2) and transforming growth factor-β1 (TGFβ1) as samples, or concanavalin A (ConA) (10 µg/ml) at a density of 1×10 6 cells/ml. Treg cells were analyzed by flow cytometry and ConA-stimulated culture supernatants were tested for concentrations of IL-4, IL-5, IL-6, IL-10, IL-13, TGFβ1, tumor necrosis factor α (TNFα) and interferon-γ (IFNγ). Results: The results for patients who underwent HCT at our institution during the same observation period as this study suggested that donor source and patient age may be involved in development of cGVHD (p=0.032, p=0.015, respectively). In younger patients, CD4/8 in peripheral blood showed a tendency to increase over time after transplantation: 0.91±1.0 at 200 days, 0.54±0.29 at 2 years, and 1.32±0.57 at 3 years (R=0.308, p=0.072); and young patients after cord blood transplantation showed a marked improvement: 0.30±0 at 200 days, 0.59±0.18 at 2 years, and 1.84±0.27 at 3 years (R=0.913, p=0.0016). Percentages of Treg cells in peripheral blood and stimulated cultures were positively correlated in younger (R=0.349, p=0.043) and older (R=0.381, p=0.029) patients. The percentage, absolute number, and amplification rate of Treg cells in stimulation culture of T cells from younger patients (6.37±4.02%, 3759.4±1963.3 /mL, 12.4±11.5 times) at 200 days after transplantation were significantly higher than those for older patients (3.04±1.48%, 1783.9±1152.0 /mL, 5.4±3.7 times) (p=0.027, p=0.003, p=0.023). Post-transplant Treg cell expansion rates in younger cord blood transplant recipients significantly increased by 2.4±0 times at 200 days, 2.8±0.6 times at 2 years, and 5.8±2.1 times at 3 years (R=0.711, p=0.046). Regarding cytokine production, IL-5 in stimulation culture from younger patients showed a tendency to increase over time: 4.75±8.89 pg/mL at 200 days, 20.04±27.20 pg/mL at 2 years, and 59.51±104.93 pg/mL at 3 years (R=0.294, p=0.087). Conclusions: T cell reconstitution and cytokine production tended to increase over time after transplantation in younger patients. The ability to reconstitute Treg cells was higher in younger patients early after transplantation and increased over time in young cord blood transplant recipients. These factors may account for the high incidence of cGVHD in older transplant recipients from adult donors, although the number of cases in the study is limited and the data are preliminary.

Cryopreservation Impacts Allogenic Stem Cell Engraftment: Relation between Graft Quality Control and Post-Transplant Clinical Outcome

Introduction: Freezing hematopoietic stem cells (HSC) has been a standard procedure in cellular therapy, either for allogenic, autologous, or cord blood transplantation. While cryopreservation is generally reported in the literature as a safe procedure with little impact on graft quality, some reports suggest significant effects of cryopreserved HSC as compared to fresh cells in the outcome of Hematopoietic Stem Cell Transplantation (HSCT). Recently, the COVID-19 pandemic enforced cryopreservation of HSC to secure allograft transplantation from related and unrelated donors. Modifying our standard practices was a unique opportunity to analyze the impact of this additional procedure on cell quality and HSC engraftment. Method: This study compared the HSCT engraftment from fresh versus cryopreserved allogeneic HSC performed in Necker Hospital (n = 236) between January 2020 to December 2022. We retrospectively collected clinical data on patients from our unicentric PROMISE database and extracted the graft characteristics (cell phenotypes, viability, and clonogenicity) from the quality assurance database. Delayed platelets or neutrophils recoveries, early graft loss, and the need for CD34+ selected stem cell boost were used to define post-transplant graft dysfunctions. Results: 107 pediatric patients with a median age of 3.9 years old and 129 Adult patients underwent primary HSCT in our center during the COVID-19 pandemic. Indications were hematological malignancies (n= 97: Acute leukemia, myelodysplastic syndrome, lymphoma, plasma cell disorders), inborn error diseases (n= 131: primary immune deficiency, hemoglobin disorder, histiocytic disorder), and bone marrow failure (n= 8). Sixty six (28.0%) graft of hematopoietic stem cells were cryopreserved from Bone Marrow (BM) (n = 18, 14.8%) and Peripheral Blood Stem Cells (PBSC) (n = 48, 42.1%). Cryopreservation significantly affects the viability (98.2% fresh vs. 84.4% cryopreserved HSC, p<0.0001) and the clonogenicity (18.7% fresh vs. 8.75% cryopreserved HSC, p<0.0001), whatever the source of stem cells. While cell viability and clonogenicity complied with the international standard before graft infusion, graft dysfunctions were a significant concern for cryopreserved allogeneic transplant (n= 22; 33.3%). Graft dysfunctions in cryopreserved HSC groups occurred with both bone marrow and PBSC. Significantly, dysfunctions increased to 38.5% for cryopreserved BM despite a higher median dose of CD34+/kg infused 15.5 (range, 10.2-20.7). No quality control parameter was predictive of engraftment dysfunction. Discussion conclusion: Cryopreservation of HSC was critical during the SARS-CoV-2 pandemic; however, in our experience, the procedure could impact graft function. Considering the development and worldwide distribution of cell therapy drug products, accurately evaluating the pretransplant graft quality is an issue in predicting the engraftment of HSC.

Mismatched Unrelated Donor Transplantation with Ptcy-Based Gvhd Prophylaxis Is Associated with Better Survival Than Double Unit Umbilical Cord Blood Transplantation in Patients with AML in First CR: A Study from the ALWP of the EBMT

Background: The best donor option for acute myeloid leukemia (AML) patients lacking an HLA-matched donor has remained unknown. The recently reported BNT CTN 1101 trial observed higher non-relapse mortality (NRM) and lower overall survival (OS) in patients randomized to double-unit unrelated umbilical cord blood transplantation (dCBT) in comparison to those randomized to HLA-haploidentical bone marrow transplantation with post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis 1. In addition, recent registry studies observed at least as good transplantation outcomes in AML patients given grafts from 9/10 HLA-matched unrelated donor (UD 9/10) with PTCy-based GVHD prophylaxis as those given grafts from HLA-haploidentical donors 2,3. These observations prompted us to perform a retrospective registry study comparing hematopoietic cell transplantation (HCT) outcomes between UD 9/10 and dCBT. Methods: Inclusion criteria consisted of adult patient, AML in CR1 at transplantation, either peripheral blood stem cells (PBSC) from UD 9/10 with PTCy as GVHD prophylaxis or dCBT, transplantation between 2013 and 2021, and no in vivo T-cell depletion. Results: A total of 208 dCBT patients and 270 UD 9/10 allo-HCT were included. The 180-day cumulative incidence of grade II-IV acute GVHD was 29% in UD 9/10 versus 44% in dCBT recipients (P=0.001). The 2-year cumulative incidences of relapse and of NRM were 23.5% and 12.5%, respectively, in UD 9/10 recipients versus 27% (P=0.39) and 18% (P=0.07), respectively in dCBT recipients. Two-year OS and LFS were 70% and 64%, respectively, in UD 9/10 recipients versus 60% (P=0.016) and 55% (P=0.028), respectively in dCBT recipients. In multivariate analyses, in comparison with UD 9/10 recipients, dCBT patients had a higher non-relapse mortality (HR=2.35, 95% CI: 1.23-4.48; P=0.01), comparable relapse incidence (HR=1.12, 95% CI: 0.67-1.86; P=0.66), lower leukemia-free survival (HR=1.5, 95% CI: 1.01-2.23; P=0.047), and lower overall survival (HR=1.66, 95% CI: 1.08-2.55; P=0.02). Conclusions: In summary, our results suggest that transplantation outcomes are better with UD 9/10 with PTCy-based GVHD prophylaxis than with dCBT for AML patients in CR1. These data might support the use of UD 9/10 with PTCy-based GVHD prophylaxis in AML patients lacking an HLA-matched donor. References Fuchs, E. J. et al. Double unrelated umbilical cord blood vs HLA-haploidentical bone marrow transplantation: the BMT CTN 1101 trial. Blood 137, 420-428 (2021).Baron, F. et al. Comparison of HLA-mismatched unrelated donor transplantation with post-transplant cyclophosphamide versus HLA-haploidentical transplantation in patients with active acute myeloid leukemia. Bone Marrow Transplant. 57, 1657-1663 (2022).Battipaglia, G. et al. Post-transplant cyclophosphamide in one-antigen mismatched unrelated donor transplantation versus haploidentical transplantation in acute myeloid leukemia: a study from the Acute Leukemia Working Party of the EBMT. Bone Marrow Transplant. 57, 562-571 (2022).

Impact of Letermovir Prophylaxis for Cytomegalovirus Reactivation on Post-Transplant Outcomes 100 Days before and after Allogeneic Hematopoietic Cell Transplantation

Background: Cytomegalovirus (CMV) infection is a major infectious complication following allogeneic hematopoietic cell transplantation (allo-HCT). Although letermovir (LMV) prophylaxis dramatically reduces the incidence of early clinically significant CMV (csCMV) infection, it remains unclear whether it has a beneficial effect on nonrelapse mortality (NRM) and overall survival (OS). Additionally, because the incidence of csCMV infection increases after completing LMV prophylaxis, the impact of late csCMV infection beyond 100 days after transplantation on posttransplant outcomes should also be verified. Study Design: We included adult patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML), or myelodysplastic syndrome (MDS) aged ≥16 years who underwent allo-HCT between 2017 and 2019. These patients' data were obtained from the registry database of the Japanese Society for Transplantation and Cellular Therapy (JSTCT). Results: Donor CMV seronegativity (D-CMV −)/recipient CMV seronegativity (R-CMV −) was recorded in 558 cases (9.3%), and R-CMV +/D-CMV + or - was recorded in 4,562 cases (78.0%). The median age was 51 (range, 16-80) years. The median follow-up length was 389 (range, 0-1,334) days. LMV prophylaxis was administered to 1,640 patients (LMV group), and the median duration of LMV prophylaxis was 85 (range, 2-152) days. LMV prophylaxis significantly reduced the incidence of early csCMV infection compared with those not administered LMV prophylaxis (15.4% vs. 54.1%; p<0.01, hazard ratio [HR], 0.30; p<0.01)). However, LMV prophylaxis did not have any beneficial effect on the 1-year NRM (HR, 0.93; p=0.40) and OS (HR, 0.96; p=0.49) in multivariate analysis. The possible causes were breakthrough csCMV infection within 100 days after transplantation during LMV prophylaxis and late csCMV infection after 100 days after transplantation after completion of LMV prophylaxis. Breakthrough csCMV infection during LMV prophylaxis developed in 74 (4.5%) of the 1,640 patients who had received LMV prophylaxis. Breakthrough csCMV infection occurred at a median of 33 (range, 6-139) days after transplantation. R-CMV +, prior transplantation, cord blood (CB) transplants, anti-thymocyte globulin (ATG) or posttransplant cyclophosphamide (PTCY) use for GVHD prophylaxis, and grade II-IV acute GVHD were associated with an increased risk of breakthrough csCMV infection. The breakthrough csCMV infection group showed inferior NRM (HR, 3.44; p<0.01) and OS (HR, 1.93; p=0.02) compared with those without infection among LMV prophylaxis group. After completing LMV prophylaxis, 252 patients had late csCMV infection at a median of 134 (range, 101-405) days after transplantation. In multivariate analysis, R-CMV +, older age, CB transplantation, ATG and/or PTCY use for GVHD prophylaxis, grade II-IV acute GVHD, and LMV prophylaxis before day 100 after transplantation were associated with an increased risk of late csCMV infection. Late csCMV infection showed inferior NRM (HR, 1.83; p<0.01) and OS (HR, 1.58; p<0.01) in multivariate analysis. Conclusion: LMV prophylaxis efficiently suppressed the development of early csCMV infection; however, this effect did not translate into improved posttransplant outcomes. Breakthrough csCMV infection during LMV prophylaxis and the development of late csCMV infection after completing LMV prophylaxis worsened transplant outcomes in the LMV prophylaxis group. Further improvements in posttransplant CMV management will be required to address these issues.

The DPP4 Dependent Transcriptome Identifies Pathways to Improve Mouse Hematopoietic Cell Function

Hematopoietic cell transplantation (HCT) is a curative treatment for hematologic disorders wherein healthy donor hematopoietic stem (HSCs) and progenitor cells (HPCs) collected from bone marrow (BM), mobilized peripheral blood (PB) or umbilical cord blood (CB) reconstitute an ablated hematopoietic system. There is a strong need to enhance functional competency of HSCs/HPCs for HCT to prevent complications like graft versus host disease (GVHD), relapse, and graft failure. Dipeptidyl peptidase 4 (DPP4) is a protein that cleaves N-terminal dipeptides from hematopoietic factors, impacting their function. Inhibition of DPP4 improves HSC/HPC competency in mouse models of HCT and clinically speeds neutrophil recovery after CB transplantation and reduces incidences of GVHD after PB transplantation. Thus, DPP4 inhibition is a viable component of a multi-pronged strategy to improve engraftment and prevent GVHD. While DPP4 inhibition improved early neutrophil recovery in clinical trials, the effects were modest, required high dose treatment, and effects on platelet recovery were unclear. Examining mechanisms by which DPP4 inhibition drives HSC/HPC functional competency may yield insight into targets that can enhance DPP4 driven improvements to HCT. We harvested BM from mice treated with the DPP4 inhibitor Diprotin A (DPA) and sorted immunophenotypically defined HSCs, multipotent progenitors (MPPs), common myeloid progenitors (CMPs), and granulocyte-macrophage progenitors (GMPs) for transcriptomic analysis. Linear modeling to examine differential gene expression controlling for cell type revealed that DPP4 inhibition gave strong enrichment of gene programs associated with mitochondrial function. Using a mitochondrial stress test and the Seahorse metabolic flux analyzer, we found that lineage depleted mouse BM cells treated ex vivo with DPA had lower basal oxygen consumption rates and spare respiratory capacity. These seemingly paradoxical data are consistent with reports that highly functional HSCs have higher mitochondrial mass but exhibit less mitochondrial activity. Thus, DPP4 inhibition may preserve high levels of functional competency by reducing cellular dependence on oxidative phosphorylation. To examine DPP4 inhibition effects on individual subpopulations of HSCs/HPCs, we modeled each cell type separately for differential gene expression. We found that gene programs associated with neutrophil development were significantly enriched in HSCs and MPPs from mice treated with DPA, including genes Elane, Lcn2, Prtn3 and Ctsg/h, concomitant with downregulation of platelet development programs in HSCs and GMPs from mice treated with DPA, including genes Gp6/9, P2ry12 and Clec1b. This suggests that DPP4 drives improved engraftment in part by priming HSCs/HPCs for neutrophil recovery but does not enhance platelet development. We then sought to target a platelet activating pathway in combination with DPP4 inhibition to improve HCT. Recipient mice were treated on days -2, -1, and 0 with 75 mg/kg DPA and day 0 with 50 µg/kg and days 1, 3, 5, and 7 with 25 µg/kg recombinant human Thrombopoietin (TPO), a platelet activating agonist. On day -1 mice were lethally irradiated and transplanted via tail vein with 2.5x10 5 whole BM donor cells on day 0. Complete blood counts 2 weeks following transplantation showed that mice treated with DPA alone exhibited worse platelet recovery, in line with our transcriptomic data. However, mice treated with the combination of DPA and TPO exhibited significantly better platelet recovery than vehicle controls and DPA alone. Further, neutrophil recovery trended towards improved recovery in the combination treatment compared to the single agent treatments. Flow cytometry of the PB revealed no differences in BM homing or in donor PB chimerism one month following HCT in the combination treatment compared to single agents (though all treatments showed improved homing over vehicle controls), suggesting the primary effects were on early recovery and not on initial or long-term engraftment. These data elucidate the DPP4 dependent transcriptome in the hematopoietic compartment, providing molecular insights into genes that drive enhanced functional competency of HSCs/HPCs. We also demonstrate that the DPP4 dependent transcriptome can reveal gene programs that can be targeted in combination to provide additive improvement on transplantation recovery.

Retrospective Study of Allogeneic Hematopoietic Stem Cell Transplantation for Relapse or Refractory Peripheral T-Cell Lymphoma at Toranomon Hospital and Toranomon Hospital Kajigaya

[Background] Relapsed or refractory peripheral T-cell lymphoma (R/R PTCL) is known to have a poor prognosis. Although new medications have been introduced in recent years, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative treatment for R/R PTCL. We review the results of allo-HSCT for PTCL at our institution. [Methods] We performed a retrospective analysis of R/R PTCL patients who underwent first allo-HSCT at our hospital from February 2011 and April 2023. The primary endpoint was OS, which was defined as the time from allo-HSCT to death from any cause or the last follow-up. The secondary endpoints included progression-free survival (PFS), relapse/progression incidence (RI) and non- relapse mortality (NRM). PFS was defined as the time from allo-HSCT to relapse/progression, death, or the last follow-up. OS and PFS were estimated by the Kaplan-Meier method and multivariate Cox proportional hazard models. The cumulative incidence of relapse and NRM were investigated with a competing risk analysis using Gray's test and multivariable Fine and Gray competing risk regression. [Results] During the study period, a total of 44 patients received first allo-HSCT for PTCL (ALK positive ALCL: 2, ALK negative ALCL: 2, AITL: 10, PTCL-NOS: 21, CTCL: 7, HSTL: 2). The median follow-up months of survivors was 51.6 (range, 2.6-141.6). The median age of patients at transplantation was 50 years (range, 17-70). Clinical stage I/II at diagnosis was 10 cases, and clinical stage III/IV was 34 cases. Prognostic Index for PTCL(PIT) was score 1 in 20 cases, score 2 in 20 cases and score 3 in 3 cases. Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI) ≧ 2 was 21 cases. Performance Status (PS) 0-1 was 32 cases and PS 2-4 was 12 cases. Primary induction failure (PIF) was 28 cases and relapse after first remission (REL) was 16 cases, including 5 cases of relapse after autologous stem cell transplantation. Median number of chemotherapy regimens received before allo-HSCT was 3 (range, 1-8). Clinical stage at transplantation was CR/PR in 23 patients and SD/PD in 21 patients.The majority, thirty-two had received unrelated cord blood transplantation (CBT), six did unrelated bone marrow transplantation (uBMT), and 6 did related peripheral blood stem cell transplantation (rPBSCT). Thirty-two patients received myeloablative conditioning (MAC), eighteen of which included total body irradiation (TBI) and 15 of which included busulfan (BU). Twelve patients received reduced-intensity conditioning (RIC) . Regarding the primary endpoint, the 4-year OS after allo-HSCT was 53.3%. The 4-year PFS, RI and NRM were 50.4%, 20.7% and 28.8%, respectively. The 4-year OS of CBT, uBMT and rPBSCT patients was 55.2%, 66.7% and 33.3%, respectively. The 4-year OS of REL and PIF patients was 79.1% and 39.5%, respectively (p<0.01). The 4-year OS of MAC and RIC was 49.5% and 64.3%, respectively (p=0.58). The 4-year OS of patients with TBI was superior to patients without TBI (71.1% vs 40.3%, p=0.05). The 4-year OS of CR/PR patients at transplant was superior to SD/PD patients (67.1% vs. 42.9%, p=0.05). In the univariate analysis, PS 0-1, HCT-CI 0-1, REL, CR/PR patients at transplant, patients with TBI and patients without BU were favorable prognostic factors. In the multivariable analysis, REL was associated with better OS (p=0.01, HR 0.16; 95% CI: 0.04-0.65). Except for 3 patients who died from transplant complications before engraftment, 41 patients achieved neutrophil engraftment, with a median engraftment date of 19 days (range, 11-31 days) after transplantation. Twenty-seven patients had acute GVHD (Grade I: 3, Grade II: 13, Grade III: 8, Grade IV: 3), and 11 patients had chronic GVHD. Eleven patients relapsed after transplant, and the median time from transplant to relapse was 26.3 months (range, 0.6-87.1 months). Three patients survived at the last follow up, and the median follow-up time of survivors from relapse was 430 days (range, 12-1301). [Conclusion] Our data indicated good results of allo-HSCT for R/R PTCL, and significantly better in relapse after first remission patients.

Human Pro-T-Cell Manufacturing in Vitro Is a Safe Procedure for Hematopoietic Stem Cell Transplantation with Delayed T-Cell Reconstitution: Interim Results from 2 Different Clinical Trials

Introduction: Alternative donor Hematopoietic stem cell transplantation (HSCT) strategies are followed by a prolonged period of immune deficiency due to delayed T-cell reconstitution. Either Umbilical Cord (CB) blood transplant or CD34+ selected haplo-transplant provided similar T-cell lymphocytes (CD3+ and CD4+) recoveries at any time point, and recipients had significantly fewer CD4+ T-cells during the first six months compared to HLA-matched donors. The GMP generation of Human T lymphoid Progenitors (HTLP) that are competent to rapidly become in vivo differentiated functional and thymic-educated T-cells may overcome the post-transplant delayed immune reconstitution. Method: HTLP safety and efficacy to accelerate immune reconstitution is currently evaluated in 2 multicentric and single-arm clinical trials: after umbilical cord blood in adult hematologic malignancy (Eudract 2019-004883-23) and after partially HLA compatible CD34+ immune-selected allogeneic hematopoietic stem cell transplantation in Severe Combined Immune Deficiency (SCID) patients (Eudract 2018-001029-14). Results: We enrolled and treated six patients, 4 SCID and 2 adults with malignancy, with an average follow-up of 8.00 (range, 1.60 to 37.7) months. HTLP cell product was infused between D7 to D14 post-HSCT for SCID patients after ensuring the decrease of the ATG level while meaning for the adult patient; the expanded pro-T cells were injected at D0. The Pro-T manufacturing process allows to robustly expand CD34+ cells to HTLP with a median of 79.7% (range 54.6; 98.9) of differentiation (CD7+ CD3-) and a median fold of proliferation of 14.7 (range 8.80; 18.5). No chromosome instability was induced during the expansion. Patients received increasing doses ranging from 0.1 to 0.5 10 6 HTLP/kg. The amount of CD3+/kg was less than 11.2 (range 0; 588)/ kg. No early or mid-term toxicity due to the administration of HTLP has been reported for evaluable patients (6/6). One SCID patient died on D53 because of severe VOD. Primary engraftment was confirmed in 4 out of 5 patients. Interestingly, despite the gradual increase of doses, there was no aGVHD over grade >2. Preliminary efficacy results suggest that circulating CD3+ CD4+ TCRαβ+ T cells > 50/μl before M4 depended on the increased infused dose of HTLP and an intrathymic paracrine effect. Notably, there was no viral infection disease or relapse during the outcome. Discussion conclusion: First infusions of HTLP in both clinical trials confirmed the safety and reproducible GMP manufacturing. HLTP offers an exciting perspective for improving immune reconstitution in alternative hematopoietic transplants.

ABO Incompatibility Haploidentical Peripheral Blood Stem Cell Transplantation Combined with a Single Cord Blood Unit for Severe Aplastic Anemia Patients

Background: For young severe aplastic anemia (SAA) patients without HLA matched donors, haploidentical hematopoietic stem cell transplantation can be used as an alternative selection. The grafts of classic Beijing protocol in China is a combination of bone marrow and peripheral blood stem cell. For patients with major or minor blood type incompatibility, bone marrow stem cells need to undergo red blood cell or plasma removal treatment. There was rare reports about haploidentical peripheral blood stem cell combined with a single unrelated cord blood unit for ABO incompatibility haploidentical stem cell transplantation in SAA patients. Objective: To observe the efficacy of ABO incompatibility haploidentcial peripheral blood hematopoietic stem cell transplantation combined with a single unrelated cord blood unit for SAA patients. Method s : Fifty-five SAA patients underwent stem cell transplantation from August 2018 to February 2022 in the First Affiliated Hospital of Xi'an Jiaotong Univeristy were divided into two groups based on donor-recipient ABO compatibility, the donor-recipient ABO matched group（BM+PB group）using haploidentical bone marrow and peripheral blood stem cell as grafts, and donor-recipient ABO mismatched group（CB+PB group）, using unrelated cord blood and haploidentical peripheral blood stem cell as grafts. The differences of hematopoietic reconstitution, acute and chronic GVHD, CMV and EB virus infection, PFS, and OS between the two groups were compared. Result s : There were 30 cases in CB+PB group and 27 cases in the BM+PB group. Except for differences in donor-recipient ABO compatibility, the other characteristics of the two groups of patients were comparable((P>0.05). One patient in the BM+PB group had primary graft failure, while the rest of the patients were successfully implanted. There were no significant statistical differences in neutrophil,platelet and red blood cells recovery rates, the incidence of acute and chronic GVHD, CMV, EB virus infection, and PTLD between the two groups of patients(P>0.05). There was no significant statistical difference in OS between the two groups of patients(P>0.05)(Figure 1). Conclusion: For SAA patients with donor-recipient ABO incompatibility could use haploidentical peripheral blood cell combined with unrelated cord blood for transplantation which had compared outcome with haploidentcal bone marrow and peripheral blood cell transplantation.

Implementation and Evaluation of Discharge Planning for Patients Undergoing Umbilical Cord Blood Transplantation

Purpose The purpose of this study was to implement discharge planning for patients undergoing umbilical cord blood transplantation (UCBT) and evaluate the effects on length of stay (LOS), hospital readmission, discharge readiness, self-efficacy, and quality of life (QoL). Methods Participants (n =72) were assigned to a control group (CG: received usual care) or an intervention group (IG: received discharge planning from admission to 100 days after UCBT). LOS and the rate of hospital readmission within 30 days after discharge were collected. Discharge readiness was measured by the Readiness for Hospital Discharge Scale, self-efficacy and QoL were assessed at 100 days after UCBT using General Self-Efficacy Scale and FACT-BMT version 4. Results Sixty-six patients completed the study, the IG group showed significantly better discharge readiness (p<0.05), improvement in self-efficacy (p<0.001). Except for social and emotional well-being, all the other dimensions and three total scores of FACT-BMT in the IG were higher than the controls (p<0.05). The LOS was less in the IG (50.12±8.80 vs. 53.28±11.28, p=0.207), the rate of hospital readmission within 30 days after discharge was lower (20.59% vs. 31.25%, p=0.376), however, the differences were not significant. Conclusion This study provided the evidences on the implementation of discharge planning for patients undergoing UCBT, and suggested that nurse-led discharge planning should be incorporated into usual care for successful hospital-to-home transitions.