Haploidentical Transplantation Research Articles

Mesenchymal Stem Cells for Prophylaxis of Chronic Graft-vs-Host Disease After Haploidentical Hematopoietic Stem Cell Transplant

ImportanceChronic graft-vs-host disease (GVHD) limits the long-term benefit of haploidentical hematopoietic stem cell transplant (HSCT). This clinical trial evaluated repeated infusions of umbilical cord mesenchymal stem cells (MSCs) during the early stage (45 days and 100 days) after haplo-HSCT to prevent chronic GVHD.ObjectiveTo determine whether repeated infusions of MSCs during the early stage after haplo-HSCT decreases the incidence of severe chronic GVHD.Design, Setting, and ParticipantsThis open-label, multicenter, parallel randomized clinical trial was conducted from April 2016 to January 2022. Eligibility criteria included a diagnosis of acute leukemia and having a haploidentical, suitable related donor for HSCT. The median (range) follow-up time was 39.0 (1.5-67.0) months.InterventionsThe enrolled patients with a haploidentical relative for HSCT received the modified busulfan/cyclophosphamide + antithymocyte globulin modified regimen and standard GVHD prophylaxis. Patients were randomly chosen to receive MSCs (the MSC group) (1 × 106 cells/kg, every 2 weeks, starting from 45 days after transplant, 4 times total) or regular prophylaxis (control group).Main Outcome and MeasureThe cumulative incidence of severe chronic GVHD.ResultsOf 158 patients, 58 (36.7%) were female individuals; the median (range) age for the MSC and control groups was 28 (18-60) years and 28 (18-56) years, respectively. A total of 158 patients were screened, and 148 patients were randomly assigned to the MSC group (n = 74) or control group (n = 74) 1 day before MSCs infusion. The estimated 2-year cumulative incidence of severe chronic GVHD was 5.4% (95% CI, 1.8%-14.0%) in the MSC group and 17.4% (95% CI, 10.1%-28.5%) in the control group (hazard ratio [HR], 0.29; 95% CI, 0.10-0.88; P = .03). There was no difference between the MSC and control groups in the cumulative incidence of leukemia relapse (HR, 1.17; 95% CI, 0.55-2.47; P = .68). The cumulative incidence of stage II to IV acute GVHD in the MSC group was significantly lower than that in the control group (HR, 0.25; 95% CI, 0.09-0.67; P = .01). The MSC group had better GVHD-free and relapse-free survival rates than the control group (HR, 0.62; 95% CI, 0.39-0.98; P = .04).Conclusions and RelevanceThe results of this randomized clinical trial show that early repeated infusions of MSCs decreased the incidence and severity of chronic GVHD, and the incidence and severity of acute GVHD manifested as a better GVHD-free and relapse-free survival rate for patients after haplo-HSCT.Trial RegistrationChinese Clinical Trial Registry: ChiCTR-IIR-16007806

Expanding donor options: haploidentical transplant recipients are also highly likely to have a 7/8-matched unrelated donor

AbstractThe use of haploidentical related donor (HRD) hematopoietic cell transplants (HCTs) in the United States grew by more than fourfold in the last decade, driven mainly by use of posttransplant cyclophosphamide (PTCy)-based graft-versus-host-disease prophylaxis. However, not all patients have a suitable HRD available. In this study, we explored the existence of unrelated donors (URDs) on the National Marrow Donor Program (NMDP) registry at the 8/8- or 7/8-match level for patients receiving HRD HCT in the United States and reporting to the Center for International Blood and Marrow Transplant Research between 2013 and 2020. The data consist of 9696 HRD HCT recipients. The NMDP search prognosis score and a search simulation were used to estimate counts of URD matches on the registry. NMDP search prognosis varied by patient ancestry, with 27.5% non-Hispanic White having a good score compared with 4.6% of African American HRD HCT recipients. Overall, 34% of recipients had ≥1 8/8-matched URDs and 84% had ≥1 7/8 URDs. Recipients of older HRDs (≥35 years) had a likelihood of between 20%- 65% of having ≥5 existing 7/8-matched URDs who were aged ≤35 years. Donor-selection practices varied among the 10 highest-volume HRD centers: 6 had >20% chance of an existing 8/8-matched URD for their HRD recipients, whereas 4 centers had low likelihood of identifying an 8/8-matched URD. In conclusion, although most US patients undergoing HRD HCT do not have an existing 8/8 URD, the majority have an existing 7/8-matched URD. Studies comparing outcomes in patients receiving either HRD or 7/8-matched URD HCT and PTCy-based graft-versus-host disease prophylaxis may be warranted.

Haploidentical Stem Cell Transplantation: Half Match but More Hope!-Single Centre Experience from Western India.

With the success of post-transplant cyclophosphamide based platform and improved clinical care, the number of haploidentical stem cell transplants (HaploSCT) have surged over the last decade. However, data from India is scarce. We aimed to evaluate the outcome of haploSCT at our centre. Since the inception of government schemes, many patients at our centre are able to undergo transplantation at subsidized cost. We conducted a retrospective analysis of the haploidentical transplants performed between January 2015 and November 2022. Fifty patients were eligible for this study. Patient details were obtained from case files. The graft versus host disease (GVHD) prophylaxis was post-transplant Cyclophosphamide (PTCy) with Mycophenolate-mofetil and Cyclosporine/tacrolimus/sirolimus. All patients were transfused peripheral blood stem cells from donors. Post-transplant, patients continued regular follow up as per schedule. Supportive care was given as per unit protocol. Overall survival (OS) was calculated using the Kaplan-Meier method. Fifty patients underwent haploSCT. A total of fifty patients with a median age of 20years (range 3-53years) underwent haploidentical HSCT from a family donor. Twenty three (46%) patients were > 18years age and 82% were males. Indications for transplant included both benign and malignant hematological diseases. Most common conditioning regimen used was Fludarabine + Busulphan + Cyclophosphamide (n = 38, 76%). Thirty five patients (70%) engrafted successfully. In the patients who had successful engraftment, the median time to neutrophil engraftment was 16days (range 10-20days) and platelet engraftment was 18days (range 10-32). Fourteen patients developed acute GVHD (28%), and three patients developed chronic GVHD (6%). The median follow-up was 30months and the two-year OS was 43% with a median OS of 17months. Twenty-one (adult = 9, pediatric = 12) out of 50 patients (42%) are alive and on regular follow-up. HaploSCT with a PTCy platform is a cost-effective, promising modality of treatment in patients who have no suitable matched donors and are not affording matched unrelated transplants. At our centre, we were able to achieve acceptable results with use of generic medications at affordable cost. Transplant Related Mortality (TRM) rates were comparable to other centres, however, multi-drug resistant bacterial infection remains a challenge in performing haploidentical HSCT in developing countries.

Cerebral hemodynamic changes after haploidentical hematopoietic stem cell transplant in adults with sickle cell disease

AbstractPreliminary evidence from a series of 4 adults with sickle cell disease (SCD) suggests that hematopoietic stem cell transplant (HSCT) improves cerebral hemodynamics. HSCT largely normalizes cerebral hemodynamics in children with SCD. We tested the hypothesis in adults with SCD that cerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) measured using magnetic resonance imaging, normalized to healthy values, comparing measurements from ∼1 month before to 12 to 24 months after HSCT (n = 11; age, 33.3 ± 8.9 years; 389 ± 150 days after HSCT) with age-, race- and sex-matched values from healthy adults without sickle trait (n = 28; age, 30.2 ± 5.6 years). Before transplant, 7 patients had neurological indications for transplant (eg, overt stroke) and 4 had nonneurological reasons for haploidentical bone marrow transplant (haplo-BMT). All received haplo-BMT from first-degree relatives (parent, sibling, or child donor) with reduced-intensity preparation and maintained engraftment. Before transplant, CBF was elevated (CBF, 69.11 ± 24.7 mL/100 g/min) compared with that of controls (P = .004). Mean CBF declined significantly after haplo-BMT (posttransplant CBF, 48.2 ± 13.9 mL/100 g/min; P = .003). OEF was not different from that of controls at baseline and did not change significantly after haplo-BMT (pretransplant, 43.1 ± 6.7%; posttransplant, 39.6 ± 7.0%; P = .34). After transplant, CBF and OEF were not significantly different from controls (CBF, 48.2 ± 13.4 mL/100 g/min; P = .78; and OEF, 39.6 ± 7.0%; P > .99). CMRO2 did not change significantly after haplo-BMT (pretransplant, 3.18 ± 0.87 mL O2/100 g/min; posttransplant, 2.95 ± 0.83; P = .56). Major complications of haplo-BMT included 1 infection-related death and 1 severe chronic graft-versus-host disease. Haplo-BMT in adults with SCD reduces CBF to that of control values and maintains OEF and CMRO2 on average at levels observed in healthy adult controls. The trial was registered at www.clinicaltrials.gov as #NCT01850108.

Donor aKIR genes influence the risk of EBV and CMV reactivation after anti-thymocyte globulin-based haploidentical hematopoietic stem cell transplantation.

Hematopoietic stem cell transplantation (HSCT) offers the highest curative potential for patients with hematological malignancies. Complications including infection, graft-versus-host disease (GVHD), and relapse reflect delayed or dysregulated immune reconstitution. After transplantation, NK cells rapidly reconstitute and are crucial for immune surveillance and immune tolerance. NK cell function is tightly regulated by killer immunoglobin-like receptors (KIRs). Previous studies have revealed that donor KIRs, especially some activated KIRs (aKIRs) are closely related to transplant outcomes. Here, we performed a retrospective study, including 323 patients who received haploidentical (haplo) HSCT in our center. In univariate analysis, donor KIR2DS1, KIR2DS3 and KIR3DS1 gene protected patients with lymphoid disease from Epstein-Barr virus (EBV) and cytomegalovirus (CMV) reactivation, while donor KIR2DS1, KIR2DS5 and KIR3DS1 gene conferred a higher risk of CMV reactivation for patients with myeloid disease. Multivariate analysis confirmed that donor telomeric (Tel) B/x and KIR2DS3 gene best protected patients with lymphoid disease from EBV (p = 0.017) and CMV reactivation (p = 0.004). In myeloid disease, grafts lacking Tel B/x and KIR2DS5 gene correlated with the lowest risk of CMV reactivation (p = 0.018). Besides, donor aKIR genes did not influence the rates of GVHD, relapse, non-relapse mortality (NRM) and overall survival (OS) in this study. The reactivation of EBV and CMV was associated with poor prognosis of haplo-HSCT. In conclusion, we found that donor aKIR genes might have a synergistic effect on CMV and EBV reactivation after haplo-HSCT. Whether the influence of donor aKIR genes varies with disease types remained to be studied.

The range of haploidentical transplant protocols in sickle cell disease: all haplos are not created equally.

The ideal curative therapy for sickle cell disease (SCD) must be applicable across all ages and include individuals with strokes and preexisting heart, lung, and kidney disease. Myeloablative, matched sibling donor hematopoietic stem cell transplant (HCT) for children with SCD has shown excellent outcomes over the past 3 decades but has been restricted due to the limited availability of a human leukocyte antigen-matched sibling donor (10%-15%) and increased treatment-related death in adults with myeloablative conditioning. To overcome these 2 significant barriers to curative therapy in SCD, related haploidentical HCT has become an active area of research. The use of related haploidentical donors (first- and second-degree relatives) increases the donor pool to at least 90% of those eligible across the life span. Importantly, most adults, even with strokes or significant comorbidities, can tolerate the nonmyeloablative conditioning regimen without treatment-related death. Since 2013, at least 3 related haploidentical HCT strategies have emerged as potential curative therapies for SCD: (1) a nonmyeloablative, T-cell replete, bone marrow transplant with thiotepa and posttransplant cyclophosphamide with a goal of complete donor chimerism; (2) a nonmyeloablative, in vivo T-cell depletion, using peripheral blood stem cells (PBSCs) with a goal of stable mixed donor-recipient chimerism; and (3) a myeloablative, ex vivo T-cell depletion using PBSCs and advanced-technology graft manipulation, with a goal of complete donor chimerism. We review the similarities, differences, outcomes, and gaps in knowledge with these 3 haploidentical HCT approaches for SCD.

HLA Haplotypes and Relapse After Hematopoietic Cell Transplantation.

Recurrence of blood malignancy is the major cause of hematopoietic cell transplant failure. HLA class II molecules play a fundamental role in antitumor responses but the role of class II haplotypes is not known. HLA-DR, -DQ, -DM, and -DO allele variation was determined in 1,629 related haploidentical transplants to study the clinical significance of individual molecules and haplotypes. Outcome correlated with patient and donor variation for HLA-DRβ residue 86 (Gly/Val), HLA-DQ (G1/G2) heterodimers, and donor HLA-DM (DM11,11/nonDM11,11) molecules, and depended on patient-donor mismatching. Risks of relapse were lower for DRβ-86 GlyGly patients when the donor was GlyVal (hazard ratio [HR], 0.46 [95% CI, 0.30 to 0.68]; P < .001); GlyVal patients benefited from HLA-DRB1-matched donors, whereas no donor was superior to another for ValVal patients. G1G2 patients with G1G2-mismatched donors had lower relapse. Transplantation from donors with DMα residue 184 ArgHis was associated with higher risk of relapse (HR, 1.60 [95% CI, 1.09 to 2.36]; P = .02) relative to ArgArg. Relapse and mortality risks differed across HLA-DR-DQ-DM haplotypes. HLA class II haplotypes may be functional constituents of the transplantation barrier, and their consideration in patients and donors may improve the success of transplantation.

Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis in HLA-Matched and Haploidentical Donor Transplantation for Patients with Hodgkin Lymphoma: A Comparative Study of the Lymphoma Working Party of the European Society for Blood and Marrow Transplantation

Post-transplantation cyclophosphamide (PTCy) has emerged as a promising approach for preventing graft-versus-host disease (GVHD) in allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, there is a lack of studies examining the impact of this GVHD prophylaxis when different donor types are used in patients with Hodgkin lymphoma (HL). This study compared the outcomes of patients with HL undergoing HSCT from HLA-matched donors, including matched sibling donors (MSDs) and matched unrelated donors (MUDs), and haploidentical donors, using PTCy as the GVHD prophylaxis approach in all cohorts. We retrospectively compared outcomes of allo-HSCT from 166 HLA-matched donors (96 sibling and 70 unrelated donors) and 694 haploidentical donors using PTCy-based GVHD prophylaxis in patients with HL registered in the European Society for Blood and Marrow Transplantation database from 2010 to 2020. Compared to HLA-matched HSCT, haploidentical donor HSCT was associated with a significantly lower rate of platelet engraftment (86% versus 94%; P < .001) and a higher rate of grade II-IV acute GVHD (34% versus 24%; P = .01). The 2-year cumulative incidence of nonrelapse mortality (NRM) was significantly lower in the HLA-matched cohort compared to the haploidentical cohort (10% versus 18%; P = .02), resulting in a higher overall survival (OS) rate (82% versus 70%; P = .002). There were no significant differences between the 2 cohorts in terms of relapse, progression-free survival, or GVHD-free relapse-free survival. In multivariable analysis, haploidentical HSCT was associated with an increased risk of grade II-IV acute GVHD and NRM and worse OS compared to HLA-matched HSCT. Our findings suggest that in the context of PTCy-based GVHD prophylaxis, transplantation from HLA-matched donors appears to be a more favorable option compared to haploidentical HSCT.

Haploidentical and Matched Sibling Transplantation for Acute Myeloid Leukemia: A Hospital-Based Study.

Allogeneic peripheral blood stem cell transplantation (PBSCT) has been increasing for the last years in Latin America. The objective of this study was to describe clinical outcomes in acute myeloid leukemia (AML) receiving allogeneic PBSCT between 2013 and 2019 in a single center of Cali, Colombia. A retrospective cohort study was conducted in Fundacion Valle del Lili. Patients diagnosed with AML who received an allogeneic PBSCT between 2013 and 2019 using human leukocyte antigen (HLA)-matched sibling donors (MSDs) or haploidentical related donors (HRDs) with myeloablative conditioning regimen were included. Cases with diagnosis of promyelocytic leukemia, myelodysplastic syndrome-related AML and therapy-related AML were excluded. Data were obtained directly from the hospital PBSCT database and clinical records. A total of 50 patients were included (HRD, n = 32; MSD, n = 18). Sixty-two percent was in the first complete remission (CR1) at the time of the transplant, of which 26% were MSD and 74% were HRD. The European Group for Blood and Marrow Transplantation (EBMT) risk score was: 44% vs. 50% low, 28% vs. 28% intermediate and 28% vs. 22% high for MSD vs. HRD, respectively. Overall survival at 5 years for MSD was 62% (95% confidence interval (CI): 31-83%) and 43% (95% CI: 25-60%) for HRD. Event-free survival was 56% (95% CI: 26-78%) and 35.6% (95% CI: 18-53%), respectively. Non-relapse mortality at day-100 was 6% (95% CI: 0.8-35%) and 20% (95% CI: 9-39%). Relapse at5 years was 18% (95% CI: 4-58%) and 25% (95% CI: 10-52%). Overall mortality rate was 46%. The grade II-IV, III-IV acute graft-versus-host disease and severe chronic graft-versus-host disease was 44%, 11% and 12% for MSD, and 43%, 9% and 0% for HRD. These results underline that MSD remains the first donor choice for AML patients in CR1 when available. HRDs are still our next option among alternative donors. It is necessary to find strategies that have a positive impact on those outcomes that markedly affect the quality of allogeneic PBSCT and the prognosis of patients. Comparative, randomized, prospective studies with longer follow-up of haploidentical allogeneic PBSCT with other donor types are required to definitely establish its role among alternative donors.

Low- versus standard-dose post-transplant cyclophosphamide as GVHD prophylaxis for haploidentical transplantation.

Haploidentical haematopoietic cell transplantation (haplo-HCT) using post-transplant cyclophosphamide (PTCY) as graft-versus-host disease (GVHD) prophylaxis is the standard of care for various haematological malignancies. The original PTCY dose after haplo-HCT was 100 mg/kg, but no dose-finding studies have been performed to identify the optimal dose. We performed a retrospective analysis to compare standard-dose PTCY (100 mg/kg) with reduced-dose PTCY (80 mg/kg): 969 in the standard-dose group and 538 in the reduced-dose group. As there was a significant difference between the two groups regarding patient and transplant characteristics, we performed propensity score (PS) matching. After PS matching, 425 patients in each group were included. The probabilities of 2-year OS were 55.9% in the standard-dose group and 47.0% in the reduced-dose group (p = 0.36). The cumulative incidences of 2-year non-relapse mortality were 21.3% in the standard-dose group and 20.5% in the reduced-dose group (p = 0.55). There was no significant difference in the incidence of acute (grade II-IV 29.2% [95% CI, 24.9-33.6] vs. 25.3% [95% CI, 21.3-29.6]; grade III-IV 7.3% [95% CI, 5.1-10.0] vs. 6.6% [95% CI, 4.5-9.3]) or chronic GVHD. In conclusion, reduced- and standard-dose PTCY were comparable in terms of major clinical outcomes.

Haploidentical Donor Transplants with Cytokine Release Syndrome Have Increased Risk of Clinically Significant Early CMV Reactivation Compared with Matched Donor Transplants Receiving Post-Transplant Cyclophosphamide

Background: Post-transplant cyclophosphamide (PTCy) enables safe haploidentical stem cell transplantation by reducing graft-versus-host-disease (GVHD) but is associated with an increased risk of reactivation of Cytomegalovirus (CMV). PTCy has more recently been adopted for matched-donor transplants, where early CMV reactivation may also be more common. This suggests that CMV reactivation is a function of PTCy rather than donor source. However, other studies comparing the rates of CMV in transplants using PTCy-based prophylaxis suggested disparity in donor source may contribute to CMV reactivation. Aim: The goal of this single-centre, retrospective study was to determine if donor type had any impact on CMV reactivation in the setting of PTCy-based GVHD prophylaxis. Methods: The Alfred Hospital Bone Marrow Transplantation Unit has used PTCy for GVHD prophylaxis in both haploidentical and matched-donor allogeneic stem cell transplants (alloSCT) since 2015. A local database search identified 119 allogeneic peripheral blood alloSCT recipients receiving PTCy-based GVHD prophylaxis between February 2015 and December 2022. Matched-donor alloSCTs also received cyclosporin from Day +5 while haploidentical alloSCTs also received tacrolimus and mycophenolate from Day +5. One patient was excluded due to CMV viremia at the time of transplant. Recipients who were CMV seropositive received therapeutic dose valganciclovir 900 mg twice daily from the start of conditioning until the day prior to stem cell infusion. Prophylactic valganciclovir (900 mg daily) was planned upon engraftment for seropositive recipients and those receiving stem cells from a seropositive donor. CMV DNA PCR was performed weekly for the first 100 days post-transplant and beyond when clinically indicated. CMV viremia was defined as any positive CMV PCR (&amp;gt; 34.5 copies/mL) within the first 100 days post-transplant. Therapeutic valganciclovir was initiated for CMV viral loads (VL) &amp;gt; 1,000 copies/mL or earlier for rapidly rising VLs. Cytokine release syndrome (CRS) was defined as fever &amp;gt; 38 degrees Celsius between stem cell infusion and PTCy on Day +3 without an alternate explanation and graded according to CTCAE criteria. CMV donor and recipient negative transplants were excluded from the analysis of the impact of donor disparity on CMV reactivation. Statistical analyses included Fisher's Exact test, one-way ANOVA and Binomial Logistic Regression. Results: Transplant characteristics according to donor source were similar apart from conditioning intensity, where recipients of haploidentical stem cells were more likely to receive myeloablative conditioning (Table 1). The cumulative incidence of moderate-severe chronic GVHD was significantly higher in matched sibling transplants but overall, 12-month GVHD-free and relapse-free survival were similar. As previously reported, CRS (overall and grades II-IV) was significantly more common in haploidentical transplants. Day 100 CMV viremia rates were not statistically different between donor groups. However, haploidentical transplants trended for earlier CMV reactivation (p=0.08), and were significantly more likely to rise above 250 copies/mL (Table 1 and Figure 1). Consequently, haploidentical transplant recipients received significantly more anti-CMV therapy (p=0.009). Multivariable analysis identified haploidentical donor as a major risk factor for CMV &amp;gt; 250 (odds ratio, OR 1.24, p=0.011) and &amp;gt; 1,000 copies/mL (OR 1.41, p=0.032) while transplant for AML/MDS was negatively associated with CMV &amp;gt; 250 (OR 0.19, p=0.009) and CMV &amp;gt; 1,000 copies/mL (OR 0.16, p=0.003). CRS was significantly associated with CMV &amp;gt; 1,000 copies/mL (OR 3.33, p=0.032) but this was no longer significant in multivariable analysis due to the association with haploidentical donor transplantation. Conclusion: This single-center retrospective comparison of PTCy-based transplants shows that haploidentical transplants have increased risk of early and clinically significant reactivation of CMV. Potential explanations include increased immunosuppression with mycophenolate and the presence of CRS, where inflammatory cytokines may de-repress the CMV major immediate early promoter. Selecting this high-risk group (haploidentical transplants with CRS) may be a cost-effective use of letermovir, which can be initiated prior to engraftment.

Casting Hope, Defying Odds: Unveiling the Impact of Haplo-Identical Stem Cell Transplant in Myeloid Malignancies - a Tertiary Cancer Care Center Experience

Background &amp; Significance: Only 30% to 40% of patients in need of a curative stem cell transplant (SCT) could find a suitable matched sibling donor. For Indian patients, the likelihood of locating a 10/10 HLA identical unrelated donor within limited donor registries is approximately 14%. However, this probability has the potential to rise to 60% if registries with over 1,000,000 registered donors are available. 1,2 Consequently, there is an increasing inclination in India to perform haploidentical transplantations utilizing the post-transplantation cyclophosphamide (PTCY) platform developed by the Johns Hopkins group. 3 The outcomes of haploidentical stem cell transplantation (haplo-SCT) for the treatment of AML were enhanced in the 1990s with the introduction of a T-cell depletion (TCD) strategy followed by a myeloablative conditioning regimen. 4,5 In the last two decades, significant progress in haplo-SCT for hematological malignancies, especially AML, includes donor selection algorithms, improved grafts, GVHD prophylaxis, and enhanced immunologic recovery, benefiting patients. 6 Here, we present our experience of haplo-identical stem cell transplants in myeloid malignancies at our centre. Study design &amp; Methods: We conducted a retrospective study at our site. Patients with myeloid malignancy who underwent haplo-identical stem cell transplant between Jan 2018 - Jan 2023 were included in the study and the follow-up was done till July 2023. Haplo-identical transplants done for diagnosis other than myeloid malignancy were excluded. The objectives of the study were to assess the non-relapse mortality [NRM] rate at day +100, relapse rate, graft-versus-host disease - free relapse-free survival [GRFS] and overall survival [OS] of the study cohort. GRFS was defined as a combined outcome including mortality from any cause, recurrence of malignancy, acute GVHD of grade 3 to 4, or chronic GVHD necessitating systemic immune suppression therapy. 7 Descriptive statistics (including median, mean, and range) were used to describe the central tendency and dispersion of variables. The probability of overall survival [OS] and graft versus host disease relapse free survival [GRFS] was estimated by the method of Kaplan and Meier. Probabilities of relapse or progression of malignancy, RRM, and day-100 NRM were summarized using cumulative incidence estimates All statistical analysis were done using statistical package for social science software (SPSS 21, IBM SPSS Statistics). Results: We have analysed 29 patients with various myeloid malignancies who have underwent haploidentical SCT from Jan 2018 to Jan 2023. There were 28 AML and 1 MDS patients. The median age was 35 (range, 16 - 59) and there were 22 males and 7 females. Conditioning intensity was myeloablative in 19 (65.5%), reduced intensity conditioning (RIC) in 8 (27.6%) and NMA in 2 (6.9%) patients. There were 10 (34.5%) patients in complete remission 1(CR1) and 19 (65.5%) in CR2. Hematopoietic Cell Transplantation-specific Comorbidity Index [HCT-CI] score was as low 11 (37.9%), intermediate 8 (27.6%) and high 10 (34.5%) patients respectively. Median time to neutrophil engraftment was 16 days (range, 12 - 25) and platelet engraftment was 17 days (range, 11 - 32). Median CD34 stem cell dose was 6.25 x 10*6/kg (range, 3.1 - 8.09) x 10*6/kg. Grade II-IV acute GVHD over first +100 days post SCT was observed in 6 (20.7) patients, and grade III-IV acute GVHD and chronic GVHD at follow up of one year was 3 (10.3) respectively. CMV reactivation by +100days was seen in 18 (62.06%) patients. Relapse was seen in 10 (34.5%) patients, out of which 2 patients are alive and 8 expired due to progressive disease. At median follow up of 13 months, OS is 60.3% (CI: 39.7% - 75.9%) and GRFS is at a median follow-up of 6 month was 51.2% (CI: 35.6% - 71%). Fig:1 NRM was 10.3% and 17.24% at +100 days and at last follow-up respectively. Fig:2 Conclusion: In conclusion, our study demonstrates favorable outcomes in terms of NRM (non-relapse mortality) with a low rate of 10.3% at 100 days after haploidentical SCT. The results also show promising overall survival (OS) and GVHD-free, relapse-free survival (GRFS) rates, supporting the potential of haploidentical transplants as an effective treatment option for myeloid malignancies. Further long-term follow-up and research are needed to validate and optimize these findings.

Efficacy and Safety Analysis of Prophylactic Brentuximab Vedotin Administration after Pediatric Acute Leukemia Haploidentical Hematopoietic Stem Cell Transplantation

Objective: Acute graft-versus-host disease (aGVHD) is a common complication following allogeneic hematopoietic stem cell transplantation. Currently, the reported incidence of moderate to severe aGVHD in domestic cases is 13%-47%, while the incidence of grade III/IV aGVHD after haploidentical transplantation ranges from 7.9% to 13.8%. Severe aGVHD is one of the leading causes of early post-transplant mortality. This study aims to analyze whether the administration of Brentuximab vedotin after transplantation can reduce the incidence of aGVHD without increasing disease relapse rates and viral infections. Methods: A retrospective analysis was conducted on 50 pediatric leukemia patients who underwent haploidentical hematopoietic stem cell transplantation (HSCT) at our hospital between June 2017 and July 2022. These patients received prophylactic treatment with Brentuximab vedotin (20mg) on day +1 and day +4 post-transplantation to prevent aGVHD. The median age of the patients was 4.1 years (range: 0.6-16.0 years), with a gender ratio of 25:25 (male:female). At the time of diagnosis, the median white blood cell (WBC) count was 19.9×10 9/L (range: 2.0-863×10 9/L) for 41 patients, while the WBC count at initial diagnosis was unknown for 9 patients. Among the cases, 22 were acute lymphoblastic leukemia (ALL), and 28 were acute myeloid leukemia (AML). Before transplantation, 28 patients were in CR1, 14 in CR2, 2 in CR3, and 6 in NR. All patients received myeloablative conditioning regimens, with 33 receiving Bu/Cy, 15 receiving TBI/Cy, 1 receiving Bu/Flu, and 1 receiving TBI/Flu. The median follow-up time was 29.1 months (range: 3.1-70.1 months). Detailed patient data are presented in Table 1. Results: All 50 patients achieved 100% engraftment of white blood cells, with a median time of 15 days (range: +10 to +21 days). Platelet engraftment occurred in a median time of 9 days (range: +5 to +78 days), except for one patient who did not achieve platelet engraftment. This particular patient was diagnosed with AML and experienced hematologic relapse and extramedullary relapse before transplantation. The patient died due to disease relapse 90 days after transplantation.The incidence of aGVHD after transplantation was 44%, with 28% experiencing grade I-II and 16% experiencing grade III-IV aGVHD. The incidence of CMV viremia was 40%, with a median time to diagnosis of 36 days (range: +19 to +84 days), while the incidence of EBV viremia was 8%, with a median time to diagnosis of 47 days (range: +14 to +87 days). During the follow-up period, five patients experienced disease relapse, with a median time to relapse of 92 days after transplantation (range: +67 to +181 days). Among the relapsed patients, 2 had ALL (both in CR2), and 3 had acute myeloid leukemia (all in NR). Seven patients died during the follow-up, including 4 with AML and 3 with ALL. The causes of death were disease relapse in 3 cases, infection in 2 cases, TMA in 1 case, and cGVHD in 1 case. The estimated 5-year overall survival (OS) and leukemia-free survival (LFS) rates were 86%, and the 5-year cumulative relapse rate was 10% (see Figures 1, 2, and 3). In comparison, a control group of 44 pediatric acute T-cell lymphoblastic leukemia patients who underwent haploidentical transplantation without prophylactic Brentuximab vedotin treatment between January 5, 2021, and June 30, 2022, were analyzed. In the control group, the incidence of aGVHD was 56.8% (P=0.007), with 36.4% experiencing grade I-II and 20.4% experiencing grade III-IV aGVHD. The incidence of CMV viremia was 68.2% (P=0.006), and the incidence of EBV viremia was 29.5% (P=0.007). The relapse rate was 15.9%, and the mortality rate was 27.3%. Conclusion: For pediatric acute leukemia haploidentical HSCT, the administration of Brentuximab vedotin (20mg) on days +1 and +4 after transplantation, in addition to conventional aGVHD prophylaxis (CsA+MMF+sMTX), significantly reduced the overall incidence of aGVHD and grade I-II aGVHD. Administering Brentuximab vedotin on days +1 and +4 did not increase the rates of CMV or EBV infection nor did it increase the risk of disease relapse.

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

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

Early Hematopoietic Reconstitution Status after Haploidentical Transplantation in AML Patients Is Indicative of Early Complications

Objective To investigate the early hematopoietic reconstruction process of haploidentical allogeneic hematopoietic stem cell transplantation (haplo-allo-HSCT) in patients with acute myeloid leukemia, and to explore its correlation with the occurrence of early complications after transplantation. Methods A retrospective analysis was performed on the clinical information of 187 AML patients who underwent haploidentical allo-HSCT at the Hematology Hospital of the Chinese Academy of Medical Sciences from January 2017 to December 2022, and all of these patients achieved complete remission before transplantation. The results of pre-transplantation-7d-after-tranplantation+14d blood routine were analyzed. The occurrence of aGVHD within 100 days after transplantation was the primary outcome event, and CMV infection within 60 days was the secondary outcome event. The diagnosis and grading of aGVHD is described in Glucksberg and MAGIC. R-4.2.0 statistical software was used for statistical analysis. Results A total of 187 AML patients who underwent haploid transplantation after achieving complete remission were included, with a median age of 35 (27-55) years, including 105 male patients (56.31%) and 82 female patients (43.69%). All patients were grouped into aGVHD patients according to different risk levels: (1) There were differences between the I~IV°aGVHD group and the patients without aGHVD (100 versus 87 patients) in the early post-transplantation plt and WBC absolute levels, and the I~IV°aGVHD group showed a lower plt trend in 1d and 2d, and a higher WBC level (0.08×10 9/L vs 0.07×10 9/L, p=0.036) at 10 days. (2) Compared with patients without aGHVD (70 versus 87 cases), the former showed lower plt levels (62.5×10 9/L vs 80×10 9/L, p=0.029) in 1d and higher WBC levels (0.03×10 9/L vs 0.02×10 9/L, p=0.047; 0.11×10 9/L vs 0.07×10 9/L, p=0.033) in 9d~10d), the Hb level was lower at 1d~3d (91g/L vs 99g/L, p=0.047; 91g/L vs 97.5g×109/L, p=0.039; 89.5g/L vs 95.5g/L, p=0.013). (3) Compared with patients without aGHVD (33 versus 87 patients), the III~IV°aGVHD group showed lower plt levels (60×10 9/L vs 74×10 9/L, p=0.006; 48×10 9/L vs 52×10 9/L, p=0.018; 26×10 9/L vs 36.5×10 9/L, p=0.003) in 1~3d, and high WBC level (0.04×10 9/L vs 0.02×10 9/L, p=0.025; 0.14×10 9/L vs 0.07×10 9/L, p=0.008) showed in 10 days, and lower Hb level in 1d~3d (89g/L vs 99g/L, p=0.047; 89g/L vs 97.5g/L, p=0.039; 83g/L vs 95.5g/L, p=0.013). Based on the maintenance of platelets at 20×109/L for 3 days after transplantation, the cumulative incidence of 100 days III~IV°aGVHD in the ≤3d group was higher (63% vs 30%, p=0.015). Univariate analysis showed that the absolute value of 1~3d plt after transplantation was low, and the PLT maintained at 20×10 9/L after HSCT was short, which was a risk factor for the occurrence of aGVHD. Group analysis of CMV occurring within 60 days showed that in the early post-transplantation period, patients in the non-CMV group had higher absolute platelet values (63.50×10 9/L vs 47.00×10 9/L, p=0.03) than patients in the CMV group at 0 days. Age, pretreatment regimen, transplant type, aGVHD prevention regimen, time to first PLT infusion after transplantation, absolute value of 0 d platelets, and platelet transfusion efficiency were included in univariate and multivariate analysis, and multivariate analysis showed that pretreatment regimen (p=0.017, 1.002 [0.606-0.953]) and transplant type (p&amp;lt;0.001, 0.264 [0.147-0.476]) were independent risk factors affecting the occurrence of CMV. No correlation between platelet transfusion efficiency and PLT infusion frequency and CMV was found. Conclusion Early hematopoietic reconstruction after transplantation in AML-CR patients who received haploid transplantation has certain indicative significance for the occurrence of early complications, and its indicative significance becomes more significant with the increase of aGHVD degree.

Effect of HLA-DPB1 Mismatch on Incidence and Severity of Chronic Graft-Versus-Host Disease Following Haploidentical Transplantation

Chronic graft-versus-host disease (cGVHD) is an important cause of late morbidity and mortality after haploidentical donor transplantation (HIDT), occurring in up to one-third of patients. The treatment of cGVHD can continue for years and can significantly impact quality-of-life in long-term transplant survivors. Therefore, it is important to identify risk factors that are associated with the incidence and severity of cGVHD. To this end, we investigated 335 consecutive recipients of HIDT utilizing post-transplant cyclophosphamide (PTCy) from 2005-2021, with a particular focus on class II HLA mismatches given prior published associations of HLA-DR and -DP mismatches with HIDT outcomes. HIDT recipients had a median age of 50 (19, 80). PBSC was the graft source in 81%, and conditioning was myeloablative in 49%. Whereas the incidence and severity of cGVHD did not differ between transplants with or without an HLA-DRB1 or -DQB1 allele-level mismatch, the presence of an HLA-DPB1 mismatch was associated with higher 1-yr incidence of all-grade (32% vs. 22%, p=0.07) and moderate-to-severe (22% vs. 12%, p=0.011) cGVHD (see figure). The effect of HLA-DPB1 mismatch on cGVHD was independent of permissiveness by the T cell epitope (TCE) algorithm or the vector of the mismatch (bidirectional, GVH- or HVG-only). In multivariate analysis, an HLA-DPB1 mismatch was associated with an increased risk of moderate-to-severe cGVHD (HR 2.05, p=0.044), while controlling for other covariates (CMV status, year of transplant). Other class II loci (HLA-DRB1 and HLA-DQB1) mismatching were not associated with chronic GVHD incidence in MVA. In summary, the presence of an HLA-DPB1 mismatch is associated with an increased incidence of moderate-to-severe cGVHD following PTCy-based HIDT. This effect, of course, must be balanced by the protective effect of a TCE nonpermissive HLA-DPB1 mismatch on relapse and survival, when selecting the optimal haploidentical donor.

A Single Center Retrospective Study on the Efficacy of Haploidentical Hematopoietic Stem Cell Transplantation in Patients with Myeloid Neoplasms over 50 Years Old

Objective: This study aims to evaluate the efficacy and safety of haploidentical hematopoietic stem cell transplantation in patients with myeloid neoplasms over 50 years old, and to compare the differences in survival, recurrence, and adverse reactions between patients aged 50-55 and over 55 years old. Methods: The patients with myeloid neoplasms over 50 years old who received haploidentical hematopoietic stem cell transplantation from November 2016 to December 2021 in the Bone Marrow Transplantation Center of the First Affiliated Hospital, Zhejiang University, School of Medicine were enrolled. According to the age at the time of transplantation, patients were divided into Group A (50-55 years old) and Group B (≥ 55 years old). The differences in Overall survival (OS), progression free survival (PFS), non-relapse mortality (NRM), cumulative incidence of relapse (CIR), incidence of graft versus host disease (GVHD), and infection rate between the two groups were analyzed. Results: A total of 163 patients (group A, n=77; group B, n=86) were enrolled, including 112 cases of acute myeloid leukemia (AML), 39 cases of myelodysplastic neoplasms (MDS), 4 cases of chronic myeloid monocyte leukemia (CMML), 3 cases of primary myelofibrosis (MF), and 5 cases of chronic myeloid leukemia (CML). There were no statistically significant differences in baseline data between the two groups, including follow-up time, disease categories, HCT-CI score, remission status of AML patients, minimal residual lesion (MRD) level of AML patients, and IPSS-R score of MDS patients. However, more patients in Group A received myeloablative (MAC) conditioning than patients in Group B (92.2% vs 50%, P=0.000). The median follow-up time was 741 (7-2377) days. The overall 2-year OS is 73.0% ± 3.5%, 2-year PFS is 71.3% ± 3.6%, 2-year NRM is12.23%（7.65%-17.93%）, and 2-year CIR is 17.20%（11.64%-23.69%）. All patients in group A achieved hematopoietic reconstitution except one patient died of graft failure, while 5 patients of group B died of graft failure(P=0.126). Neutrophils and platelet reconstruction in Group B was slightly longer than in Group A. The neutrophils reconstruction occurred at a median of 12 (8-20) day and 13 (9-25) day, respectively (P=0.007), and platelet reconstruction occurred at a median of 12 (9-28) day and 13 (8-37) day, respectively (P=0.055). The 2-year OS of Group A and Group B was 76.6% ± 4.8% and 69.0 ± 5.1%, respectively (P=0.199); The 2-year PFS was 76.2% ± 4.9% and 66.9 ± 5.1%, respectively (P=0.236); The 2-year NRM was 9.16% (4.00% -16.96%) and 18.61% (11.18% -27.51%), respectively (P=0.094); The 2-year CIR was similar, with 14.66% (7.74% -23.67%) and 19.16% (11.48% -28.33%), respectively (P=0.782). Interestingly, there was a difference in NRM between patients receiving reduced-intensity (RIC) and MAC conditioning in Group B, which was 10.2% (3.69% -20.61%) and 25.58% (13.64% -39.34%), respectively (P=0.043), while there was no difference in CIR, which was 17.31% (7.88% -29.80%) and 18.90% (8.71% -32.06%), respectively (P=0.933). It is suggested that in older patients, the strength of conditioning regimen has a greater impact on NMR. The incidence of grade 3-4 aGVHD within 100 days in all patients was 11.84% (7.31% -17.56%), and the incidence of 2-year intensive cGVHD was 8.19% (4.58% -13.14%). The incidence of grade 3-4 aGVHD within 100 days was similar between the two groups, with 9.46% (4.13% -17.46%) and 14.10% (7.46% -22.81%) (P=0.368), respectively. The 2-year intensive cGVHD was 8.07% (3.26% -15.72%) and 8.28% (3.62% -15.42%) (P=0.890), with similar incidence rates. The incidence of bacterial septicemia, pneumonia, invasive fungal infection, herpes virus and other infections were similar in both groups. Univariate and multivariate analysis both showed that 50-55 years old was an independent protective factor of OS (2.384 (1070-5.312), P=0.034) and GRFS (2.683 (1.181-6.094), P=0.018) in AML patients. Conclusion: Haploidentical hematopoietic stem cell transplantation is an effective and safe treatment for myeloid neoplasms over the age of 50. Compared with patients aged 50 to 55 years old, patients with myeloid neoplasms aged over 55 years old had similar efficacy and safety. The impact of MAC and RIC pretreatment on the prognosis of patients at different ages may be different. This retrospective study is limited in number and needs more cases and prospective cohort study to further verify.

Memory T Cell Donor Lymphocyte Infusion As a Treatment for Viral Reactivations after Pediatric Haploidentical Hematopoietic Stem Cell Transplant

Introduction Viral reactivations, including cytomegalovirus (CMV), Epstein-Barr virus (EBV), adenovirus (ADV), human herpesvirus 6 (HHV6), and BK virus (BKV), constitute significant infectious complications following pediatric hematopoietic stem cell transplant (HSCT). abT cell depletion of haploidentical graft prevents risk of graft-versus-host disease (GVHD) but leads to delayed immune recovery and increased risk of viral reactivations. Donor lymphocyte infusion (DLI) with CD45RA-depleted memory T cells has been reported as an effective method to rapidly recover T cell immunity post HSCT. We hereby report the experience of CD45RA-depleted memory T cell infusion to treat viral reactivation following pediatric abT cell depleted haploidentical HSCT in our center over the last three years. Methods We retrospectively reviewed pediatric patients with abT cell depleted haploidentical transplant from related donors in our center from 2021-2023, and those who received memory T cell DLI for one or more viral reactivations. We routinely infuse CD45RA depleted memory T cells (dose at 1x10 6 CD3 T cells/kg) on the day of stem cell infusion prophylactically. Surplus of memory T cells harvested was cryopreserved for future use. Viral reactivations were monitored regularly after transplant by blood PCR assays (twice weekly for CMV; once weekly for EBV, ADV, and HHV-6). BK virus of urine and blood were monitored if patients became symptomatic for hemorrhagic cystitis. Once virus reactivation is identified, we start antiviral medications and infuse cryopreserved donor memory T cells for treatment. If subsequent virus PCR tests remain positive, donor memory T cells are infused every 1-2 weeks until the test is negative. Results A total of 52 memory T cell infusions were administered to 22 patients for viral reactivation after HSCT. Half of the patients (n=11) required only one infusion for viral clearance, whereas the other half received memory T cell infusion for 2-9 times. 19 patients (86.4%) are alive at time of data collection and analysis (July 2023), and 18 patients (81.8%) are in complete remission. The characteristics of patients and transplants are summarized in Table 1. The viral reactivations, which are intended to treat, include CMV (57.7%), EBV (7.7%), ADV (23.1%), BKV (15.4%) and HHV6 (9.6%), and some patients suffered from multiple viral reactivations at the time of memory T cell infusion (so the total percentage is more than 100%). The median day of memory T cell infusion post-transplant was day 46 (range 4-183). The median and most commonly used cell dose was 2 (0.025 - 20.5) x 10 6/kg CD3+ memory T cells (CD45RA depleted). The median duration to achieve negative PCR test for each virus are 13 days (CMV), 24 days (EBV),72 days (ADV), 15 days (HHV-6) and 88 days (BKV) (Figure 1). Thus most of the patients were CMV PCR negative within 15 days after DLI. All DLI were well tolerated. One patient (4.5%) was reported to suffer from stage 2 skin GVHD post donor memory T cell infusion. Conclusions CD45RA-depleted donor memory T cell infusion is a safe, feasible and effective treatment for viral reactivation following pediatric haploidentical stem cell transplant.

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&amp;gt;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&amp;gt;0.05). There was no significant statistical difference in OS between the two groups of patients(P&amp;gt;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.

Impact of Immunosuppression Intensified Conditioning Regimen for Patients with Strong Positive Pre-Transplantation Donor Specific Anti-HLA Antibodies (DSAs) Undergoing Haploidentical Hematopoietic Stem Cell Transplantation

Objective: Immunosuppression intensified conditioning regimen has been applied for 10 patients with strong positive pre-transplantation Donor specific Anti-HLA Antibodies (DSAs) undergoing Haploidentical Hematopoietic Stem Cell Transplantation (HSCT), its effects on engraftment of hematopoietic stem cell were examined. Methods: Characteristics of 10 consecutive patients with strong positive pre-transplantation DSAs were retrospectively analyzed, including gender, age, diagnosis, disease status pre-transplantation, presence of DSA, conditioning regimens, engraftment, graft versus host disease (GVHD) incidence and survival. Results: Ten patients [3 males vs 7 females, median age 53.5(36-64)] received immunosuppression intensified conditioning regimen: Fludarabine plus busulfan (FluBu) combining total body irradiation and cyclophosphamide (TBI-Cy). DSA levels gradually decreased in all patients after preparative conditioning, and the mean fluorescence intensity (MFI) values dropped significantly (P＜0.003). The average MFI values dropped 40% at day 7 post-HSCT, 8 cases acquired hematopoietic reconstitution, the median time of neutrophil engraftment was 15.6(10-16) days, and 19(13-22) days for platelet engraftment. One case had primary graft failure and another one had poor graft function. After a median follow-up of 12.5(1.5-27) months, 7 cases remained in disease remission state with negative DSA assay, including 2 cases with MFI values higher than 20000 pre-transplantation. Conclusions：Immunosuppression intensified conditioning regimen can efficiently decrease the Donor specific Anti-HLA Antibodies (DSA) level, which leads to lowered chances of primary graft failure.