Prospective Randomized Study Comparing Myeloablative Unrelated Umbilical Cord Blood Transplantation versus HLA-Haploidentical Related Stem Cell Transplantation for Adults with Hematologic Malignancies

Improving Unrelated Donor Equity: Assessing Mismatched Donor Opportunities with Real-World Data in a Minority-Predominant Cohort

Recent advances in graft-versus-host disease (GVHD) prophylaxis including post-transplant cyclophosphamide (PTCy) and abatacept have significantly improved outcomes following HLA-mismatched allogenic hematopoietic stem cell transplantation (allo-HSCT) and have tremendous potential for reducing racial disparities in donor availability. A recent small study employing bone marrow as the source of stem cells showed similar outcomes after 5/8 versus 7/8 matches and is currently being tested in a larger study using peripheral blood stem cells. In this study, we examine real-world alternative donor HSCT options for a minority-predominant cohort in the Bronx, NY, focusing on the availability of lesser-matched (5/8 to 7/8) donors. Records of patients who underwent HLA typing at Montefiore Medical Center (2019 to 2022) were reviewed. The National Marrow Donor Program registry was queried to evaluate the availability of donors with at least 99% likelihood of HLA match at various levels (5/8, 6/8, 7/8, 8/8). Two hundred forty-one patients were included, 70% were non-White. Although the availability of ≥7/8 donors was less common in non-White patients, 100% of patients from each group had at least one or more 5/8 and 6/8 HLA-matched donors and more than 80% of these patients had >100 potential 5/8 and 6/8 HLA-matched donors. There was no statistical difference by race or ethnicity in the mean number of donors at 5/8 and 6/8 HLA-match levels. We demonstrate through real-world data that patients from diverse ethnic and racial backgrounds have access to 5/8 and 6/8 HLA-matched donors for allo-HSCT, potentially eliminating disparities in donor availability and allowing prioritization of other donor selection characteristics such as donor age, sex, ABO, and B leader matching. Further work is needed to study whether the use of mismatched donors offers a more potent graft-versus malignancy effect and optimal GVHD prophylaxis.

Human Leukocyte Antigen-Haploidentical Haematopoietic Stem Cell Transplantation Using Post-Transplant Cyclophosphamide for Paediatric Haematological Malignancies

The use of human leukocyte antigen (HLA)-haploidentical haematopoietic stem cell transplantation (HSCT) with post-transplant cyclophosphamide (PTCY), which markedly reduces the risk of graft-versus-host disease, has rapidly increased worldwide, even in children. It was initially developed for post-transplant relapse or non-remission at transplant for patients with high-risk haematologic malignancies. However, this strategy is currently used more frequently for standard-risk, transplant-eligible paediatric haematological malignancies. It has recently been recognised in adults that the transplant outcomes after PTCY-based HLA-haploidentical HSCT are comparable with those achieved after HLA-matched HSCT. Therefore, even in children, parental donors who are HLA-haploidentical donors and cord blood are currently considered the next donor candidates when an HLA-matched related or unrelated donor is unavailable. This review addresses the current status of the use of haplo-HSCT with PTCY for paediatric haematologic malignancies and future directions for donor selection (sex, age, ABO blood type, and HLA disparity), donor source, the dose of infused CD34+ cells, optimal conditioning, the concomitant graft-versus-host disease prophylaxis other than PTCY, and the pharmacokinetic study of CY and CY metabolites. These aspects present key solutions for further improvements in the outcomes of haplo-HSCT with PTCY for paediatric haematological malignancies.

Recent advances in allogeneic transplantation for acute myeloid leukemia

PURPOSE OF REVIEW

This review highlights recent advancements in allogeneic hematopoietic stem cell transplantation (allo-HSCT) for patients with acute myeloid leukemia (AML).

RECENT FINDINGS

Important improvements have been observed throughout the allo-HSCT procedure and patient management. Universal donor availability and reduced risk of graft-versus-host disease (GVHD) have been achieved with the introduction of posttransplant cyclophosphamide for GVHD prophylaxis. It has contributed, together with advances in conditioning regimens, GVHD treatment and supportive care, to a reduced overall toxicity of the procedure. Relapse is now the most frequent cause of transplant failure. With increased knowledge of the biological characterization of AML, better prediction of transplant risks and more profound and standardized minimal residual disease (MRD) monitoring, pharmacological, and immunological strategies to prevent relapse are been developed.

SUMMARY

Allo-HSCT remains the standard of care for high-risk AML. Increased access to transplant, reduced toxicity and relapse are improving patient outcomes. Further research is needed to optimize MRD monitoring, refine conditioning regimens, and explore new GVHD management and relapse prevention therapies.

Hematopoiesis in the spleen after engraftment in unrelated cord blood transplantation evaluated by 18F-FLT PET imaging

Cord blood is an important donor source for allogeneic hematopoietic stem cell transplantation (allo-HSCT), with its unique composition and quality of hematopoietic cells. The proliferation site and potency of infused hematopoietic stem cells in humans may vary between stem cell sources. We investigated this possibility in a prospective, exploratory study to assess hematopoietic dynamics using the radiopharmaceutical 3'-deoxy-3'-18F-fluorothymidine (18F-FLT), a thymidine analog used in positron emission tomography imaging, before allo-HSCT and on days 50 and 180 after allo-HSCT. We evaluated 11 patients with hematological malignancies who underwent allo-HSCT [five with peripheral blood stem cell transplantation (PBSCT) and six with unrelated cord blood transplantation (UCBT)]. Before allo-HSCT, 18F-FLT uptake did not differ between the two groups. At day 50, 18F-FLT uptake in the spleen was significantly greater in the UCBT group than in the PBSCT group (p = 0.0043), with no difference in whole-body bone marrow. At day 180, the differences in spleen uptake had diminished, and there were no differences between groups in whole-body bone marrow or the spleen, except for the sternum. The persistence of splenic hematopoiesis after engraftment in the UCBT group may reflect the complex systemic homing and proliferation mechanisms of cord blood hematopoietic cells.

Reduced Incidence of Neurologic Complications after Allogeneic Hematopoietic Stem Cell Transplantation with Calcineurin-Free Graft-versus-Host Disease Prophylaxis

Calcineurin inhibitors (CNIs), including cyclosporine and tacrolimus, are frequently associated with neurologic complications after allogeneic hematopoietic stem cell transplantation (HSCT). However, there is a lack of studies comparing the incidence and characteristics of neurologic complications in patients undergoing HSCT based on CNI-free or CNI-based GVHD prophylaxis. This retrospective single-center study analyzed the neurologic complications in 2 cohorts of patients undergoing HSCT with either CNI-based GVHD prophylaxis (n = 523) or CNI-free prophylaxis with post-transplantation cyclophosphamide, sirolimus, and mycophenolate mofetil (n = 371). The latter cohort included older patients and received more reduced-intensity conditioning and transplants from matched unrelated and haploidentical donors. The 2-year cumulative incidence of neurologic complications was significantly lower in the CNI-free cohort (6.9% versus 11.9%; P = .016), and GVHD prophylaxis was the sole statistically significant variable in multivariate analysis (hazard ratio, 2.2; 95% confidence interval [CI], .25 to 3.13; P = .0017). The distribution of neurologic types was similar in the 2 cohorts, with encephalopathy the most prevalent complication, except for headaches and myopathy, which decreased equally from 15% in the CNI-based cohort to 4% in the CNI-free cohort. Neurologic complications had negative impacts on mortality and survival rates, with a significantly higher 2-year cumulative incidence of nonrelapse mortality (NRM) (44% [95% CI, 34% to 54%] versus 16% [95% CI, 13% to 18%]; P < .0001) and inferior overall survival (66% [95% CI, 62% to 69%] versus 46% [95% CI, 37% to 58%]; P < .0001) in patients with neurologic complications. This study suggests that CNI-free GVHD prophylaxis with post-transplantation cyclophosphamide, sirolimus, and mycophenolate mofetil may reduce not only the incidence of GVHD incidence, but also the rates of neurologic complications and NRM, leading to improved survival outcomes in patients undergoing HSCT.

Early cessation of calcineurin inhibitors is feasible post-haploidentical blood stem cell transplant: the ANZHIT 1 study

Haploidentical hematopoietic stem cell transplant (haplo-HSCT) using posttransplant cyclophosphamide (PTCy) is appropriate for those who lack matched donors. Most studies using PTCy have been retrospective making conclusions difficult. ANZHIT-1 was a phase 2 study conducted at 6 Australian allogeneic HSCT centers. The primary end points were disease-free and overall survival at 2 years after HSCT. The reduced-intensity conditioning (RIC) included fludarabine, cyclophosphamide, and 200 cGy total body irradiation, and the myeloablative conditioning (MAC) was IV fludarabine and busulfan. PTCy, MMF and a calcineurin inhibitor (CNI) were used for graft-versus-host disease (GVHD) prophylaxis. CNIs were weaned and ceased by day +120 in eligible patients on day 60. Patients (n = 78) with hematological malignancies were included in the study, with a median follow-up of 732 days (range, 28-1728). HSCT was RIC in 46 patients and MAC in 32 patients. Disease-free survival probability at 2 years was 67.5% (95% [CI], 53.2-85.6) for MAC recipients and 68.3% (95% CI, 56.3-83.01) for RIC recipients. Transplant-related mortality (TRM) on day 100 and year 1 was 4.9% (95% CI, 1.6-15.3) and 17.9% (95% CI, 8.8-36.5), respectively, in the MAC group compared with 3.1% (95% CI, 0.8.1-12) and 11.6% (95% CI, 6-22.4), respectively, in the RIC group. The median time for elective cessation of CNI was day 142.5 days, with no excess chronic GVHD (cGVHD) or mortality. Of the evaluable patients, 71.6% discontinued immunosuppression 12 months after transplant. This prospective haplo-HSCT trial using PTCY demonstrated encouraging survival rates, indicating that early CNI withdrawal is feasible and safe.

The current landscape: Allogeneic hematopoietic stem cell transplant for acute lymphoblastic leukemia

One of the consistent features in development of hematopoietic stem cell transplant (HCT) for Acute Lymphoblastic Leukemia (ALL) is the rapidity with which discoveries in the laboratory are translated into innovations in clinical care. Just a few years after murine studies demonstrated that rescue from radiation induced marrow failure is mediated by cellular not humoral factors, E. Donnall Thomas reported on the transfer of bone marrow cells into irradiated leukemia patients. This was followed quickly by the first descriptions of Graft versus Leukemia (GvL) effect and Graft versus Host Disease (GvHD). Despite the pivotal nature of these findings, early human transplants were uniformly unsuccessful and identified the challenges that continue to thwart transplanters today - leukemic relapse, regimen related toxicity, and GvHD. While originally only an option for young, fit patients with a matched family donor, expansion of the donor pool to include unrelated donors, umbilical cord blood units, and more recently the growing use of haploidentical donors have all made transplant a more accessible therapy for patients with ALL. Novel agents for conditioning, prevention and treatment of GvHD have improved outcomes and investigators continue to develop novel treatment strategies that balance regimen related toxicity with disease control. Our evolving understanding of how to prevent and treat GvHD and how to prevent relapse are incorporated into novel clinical trials that are expected to further improve outcomes. Here we review current considerations and future directions for both adult and pediatric patients undergoing HCT for ALL, including indication for transplant, donor selection, cytoreductive regimens, and outcomes.

Effect of graft-versus-host disease on posttransplant outcomes following single cord blood transplantation in comparison to haploidentical transplantation with posttransplant cyclophosphamide for adult acute myeloid leukemia

BACKGROUND

The possibility that human leukocyte antigen (HLA) mismatches could reduce relapse after alternative HLA-mismatched allogeneic hematopoietic cell transplantation (HCT) is an attractive concept for acute myeloid leukemia (AML). However, it remains unclear whether the prognostic effect of graft-versus-host disease (GVHD) on survival differs between single-unit cord blood transplantation (CBT) or haploidentical HCT using posttransplant cyclophosphamide (PTCy-haplo HCT) for AML.

OBJECTIVE

The objective of this retrospective study was to compare the effect of acute and chronic GVHD on posttransplant outcomes between CBT and PTCy-haplo HCT.

STUDY DESIGN

We retrospectively evaluated the effect of acute and chronic GVHD on posttransplant outcomes following CBT and PTCy-haplo HCT in adults with AML (n=1,981) between 2014 and 2020 using a Japanese registry database.

RESULTS

In the univariate analysis, the probability of overall survival was significantly greater in patients who developed grade I-II acute GVHD (P<0.001 by log-rank test) and limited chronic GVHD (P<0.001 by log-rank test) among CBT recipients, but these effects were not significant among PTCy-haplo HCT recipients. In the multivariate analysis, in which the development of GVHD was treated as a time-dependent covariate, the effect of grade I-II acute GVHD on reducing overall mortality was significant between CBT and PTCy-haplo HCT (adjusted hazard ratio [HR] for CBT: 0.73, 95% confidence interval [CI]: 0.60-0.87; adjusted HR for PTCy-haplo HCT: 1.07, 95% CI: 0.70-1.64; p for interaction=0.038).

CONCLUSION

Our data demonstrate that grade I-II acute GVHD was associated with a significant improvement in overall mortality in adults with AML receiving CBT but not PTCy-haplo HCT.

Don't forget cord blood in non‐remission acute myeloid leukaemia !

Transplantation from haploidentical donors is widely used, with progressive reduction of cord blood (CB) as alternative donor. The paper by Matsuda and colleagues, the largest analysing the outcome in non-remission acute myeloid leukaemia (AML) transplanted with haploidentical donor or CB, suggests that CB is still a viable option when considering allogeneic transplantation for advanced AML. Commentary on: Matsuda et al. Comparison of transplant outcomes between haploidentical transplantation and single cord blood transplantation in non-remission acute myeloid leukaemia: A nationwide retrospective study. Br J Haematol. 2023;201:106-113.

In 2022, which is preferred: haploidentical or cord transplant?

Allogeneic hematopoietic stem cell transplantation is the treatment of choice for high-risk hematological malignancies such as acute myeloid and lymphocytic leukemia, myelodysplastic syndrome, and myeloproliferative disorders. Alternative donor transplantation from either haploidentical (haplo-SCT) or cord blood donor (CBT) is an established therapeutic alternative for patients who need transplants but lack a human leukocyte antigen-matched donor. Although haplo-SCT (mainly non-T-cell-depleted haplo-SCT with posttransplant cyclophosphamide) is increasing while CBT is decreasing worldwide (Figure 1), recent developments in CBT, especially cord blood expansion and other strategies to improve engraftment and immune reconstitution post-CBT, make CBT still a valuable option. This article discusses the 2 options based on the currently available data, focusing on adults, and tries to give some clues to help the transplant physician choose a haploidentical vs a cord blood donor. Given the limited numbers of published or ongoing well-designed randomized controlled trials comparing haplo-SCT to CBT and the overall similar clinical results in the available, mostly registry-based, and single-center studies, with substantial heterogeneity and variability, the decision to perform haplo-SCT or CBT in a given patient depends not only on the patient, disease, and donor characteristics and donor availability (although most if not all patients should have in principle an alternative donor) but also on the transplant physician's discretion and, most importantly, the center's experience and preference and ongoing protocols and strategies.

Umbilical cord blood: an undervalued and underutilized resource in allogeneic hematopoietic stem cell transplant and novel cell therapy applications

PURPOSE OF REVIEW

The purpose of this review is to primarily discuss the unwarranted decline in the use of umbilical cord blood (UCB) as a source of donor hematopoietic stem cells (HSC) for hematopoietic cell transplantation (HCT) and the resulting important implications in addressing healthcare inequities, and secondly to highlight the incredible potential of UCB and related birthing tissues for the development of a broad range of therapies to treat human disease including but not limited to oncology, neurologic, cardiac, orthopedic and immunologic conditions.

RECENT FINDINGS

When current best practices are followed, unrelated donor umbilical cord blood transplant (CBT) can provide superior quality of life-related survival compared to other allogeneic HSC donor sources (sibling, matched or mismatched unrelated, and haploidentical) through decreased risks of relapse and chronic graft vs. host disease. Current best practices include improved UCB donor selection criteria with consideration of higher resolution human leukocyte antigen (HLA) typing and CD34+ cell dose, availability of newer myeloablative but reduced toxicity conditioning regimens, and rigorous supportive care in the early posttransplant period with monitoring for known complications, especially related to viral and other infections that may require intervention. Emerging best practice may include the use of ex vivo expanded single-unit CBT rather than double-unit CBT (dCBT) or 'haplo-cord' transplant, and the incorporation of posttransplant cyclophosphamide as with haploidentical transplant and/or incorporation of novel posttransplant therapies to reduce the risk of relapse, such as NK cell adoptive transfer. Novel, non-HCT uses of UCB and birthing tissue include the production of UCB-derived immune effector cell therapies such as unmodified NK cells, chimeric antigen receptor-natural killer cells and immune T-cell populations, the isolation of mesenchymal stem cells for immune modulatory treatments and derivation of induced pluripotent stem cells haplobanks for regenerative medicine development and population studies to facilitate exploration of drug development through functional genomics.

SUMMARY

The potential of allogeneic UCB for HCT and novel cell-based therapies is undervalued and underutilized. The inventory of high-quality UCB units available from public cord blood banks (CBB) should be expanding rather than contracting in order to address ongoing healthcare inequities and to maintain a valuable source of cellular starting material for cell and gene therapies and regenerative medicine approaches. The expertise in Good Manufacturing Practice-grade manufacturing provided by CBB should be supported to effectively partner with groups developing UCB for novel cell-based therapies.

Single Cord Blood Transplantation Versus HLA-Haploidentical-related Donor Transplantation Using Posttransplant Cyclophosphamide in Patients With Hematological Malignancies

BACKGROUND

Unrelated cord blood (UCB) and haploidentical related donor transplantation using posttransplant cyclophosphamide (PTCy-haplo) have become alternative options to treat patients with hematological malignancies without a HLA-matched donor.

METHODS

We conducted a retrospective study using registry data from the Kyoto Stem Cell Transplantation Group for patients with hematological malignancies who received their first allogeneic hematopoietic cell transplantation using a single UCB unit (n = 460) or PTCy-haplo (N = 57) between 2013 and 2019.

RESULTS

We found that overall survival in the UCB group was comparable to that in the PTCy-haplo group (hazard ratio, 1.00; 95% confidence interval, 0.66-1.52), although neutrophil and platelet engraftment were significantly delayed. Nonrelapse mortality risk and the incidence of graft-versus-host disease in the UCB group were also comparable to those in the PTCy-haplo group. Although the relapse risk was similar between the UCB group and the PTCy-haplo group regardless of the disease risk, acute myeloid leukemia patients benefit from UCB transplant with a significantly lower relapse rate (hazard ratio, 0.38; 95% confidence interval, 0.18-0.76).

CONCLUSIONS

UCB transplant gives outcomes comparable to PTCy-haplo transplant, and both UCB and PTCy-haplo units are suitable as alternative donor sources for patients without an HLA-matched sibling or unrelated donor.

KIR in Allogeneic Hematopoietic Stem Cell Transplantation: Need for a Unified Paradigm for Donor Selection

Allogeneic hematopoietic stem cell transplantation (aHSCT) is a lifesaving therapy for hematological malignancies. For years, a fully matched HLA donor was a requisite for the procedure. However, new immunosuppressive strategies have enabled the recruitment of viable alternative donors, particularly haploidentical donors. Over 95% of patients have at least two potential haploidentical donors available to them. To identify the best haploidentical donor, the assessment of new immunogenetic criteria could help. To this end, the clinical benefit of KIR genotyping in aHSCT has been widely studied but remains contentious. This review aims to evaluate the importance of KIR-driven NK cell alloreactivity in the context of aHSCT and explain potential reasons for the discrepancies in the literature. Here, through a non-systematic review, we highlight how the studies in this field and their respective predictive models or scoring strategies could be conceptually opposed, explaining why the role of NK cells remains unclear in aHCST outcomes. We evaluate the limitations of each published prediction model and describe how every scoring strategy to date only partly delivers the requirements for optimally effective NK cells in aHSCT. Finally, we propose approaches toward finding the optimal use of KIR genotyping in aHSCT for a unified criterion for donor selection.

Results of a multicenter phase I/II trial of TCRαβ and CD19-depleted haploidentical hematopoietic stem cell transplantation for adult and pediatric patients

Hematopoietic stem cell transplantation (HSCT) from haploidentical donors is a viable option for patients lacking HLA-matched donors. Here we report the results of a prospective multicenter phase I/II trial of transplantation of TCRαβ and CD19-depleted peripheral blood stem cells from haploidentical family donors after a reduced-intensity conditioning with fludarabine, thiotepa, and melphalan. Thirty pediatric and 30 adult patients with acute leukemia (n = 43), myelodysplastic or myeloproliferative syndrome (n = 6), multiple myeloma (n = 1), solid tumors (n = 6), and non-malignant disorders (n = 4) were enrolled. TCR αβ/CD19-depleted grafts prepared decentrally at six manufacturing sites contained a median of 12.1 × 10⁶ CD34⁺ cells/kg and 14.2 × 10³ TCRαβ⁺ T-cells/kg. None of the patients developed grade lll/IV acute graft-versus-host disease (GVHD) and only six patients (10%) had grade II acute GVHD. With a median follow-up of 733 days 36/60 patients are alive. The cumulative incidence of non-relapse mortality at day 100, 1 and 2 years after HSCT was 5%, 15%, and 17% for all patients, respectively. Estimated probabilities of overall and disease-free survival at 2 years were 63% and 50%, respectively. Based on these promising results in a high-risk patient cohort, haploidentical HSCT using TCRαβ/CD19-depleted grafts represents a viable treatment option.

Comparison of haploidentical and umbilical cord blood transplantation after myeloablative conditioning

Three-year survival is similar after PTCy haplo- and UCB transplant.

Lower relapse but higher nonrelapse mortality in ≤5/8 matched UCB as compared with haplo- and 6-8/8 UCB transplant.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) has emerged as an important treatment modality. Most reports comparing haplo-HSCT with posttransplant cyclophosphamide (PTCy) and other donor sources have focused on outcomes in older adults treated with reduced intensity conditioning. Therefore, in the current study, we evaluated outcomes in patients with hematological malignancy treated with myeloablative conditioning prior to haplo- (n = 375) or umbilical cord blood (UCB; n = 333) HSCT. All haplo recipients received a 4 of 8 HLA-matched graft, whereas recipients of UCB were matched at 6-8/8 (n = 145) or ≤5/8 (n = 188) HLA antigens. Recipients of 6-8/8 UCB transplants were younger (14 years vs 21 and 29 years) and more likely to have lower comorbidity scores compared with recipients of ≤5/8 UCB and haplo-HSCT (81% vs 69% and 63%, respectively). UCB recipients were more likely to have acute lymphoblastic leukemia and transplanted in second complete remission (CR), whereas haplo-HSCT recipients were more likely to have acute myeloid leukemia in the first CR. Other characteristics, including cytogenetic risk, were similar. Survival at 3 years was similar for the donor sources (66% haplo- and 61% after ≤5/8 and 58% after 6-8/8 UCB). Notably, relapse at 3 years was lower in recipients of ≤5/8 UCB (21%, P = .03) compared with haplo- (36%) and 6-8/8 UCB (30%). However, nonrelapse mortality was higher in ≤5/8 UCB (21%) compared with other groups (P < .0001). These data suggest that haplo-HSCT with PTCy after myeloablative conditioning provides an overall survival outcome comparable to that after UCB regardless HLA match group.

Omidubicel vs standard myeloablative umbilical cord blood transplantation: results of a phase 3 randomized study

Omidubicel is an ex vivo expanded hematopoietic progenitor cell and nonexpanded myeloid and lymphoid cell product derived from a single umbilical cord blood unit. We report results of a phase 3 trial to evaluate the efficacy of omidubicel compared with standard umbilical cord blood transplantation (UCBT). Between January 2017 and January 2020, 125 patients age 13 to 65 years with hematologic malignancies were randomly assigned to omidubicel vs standard UCBT. Patients received myeloablative conditioning and prophylaxis with a calcineurin inhibitor and mycophenolate mofetil for graft-versus-host disease (GVHD). The primary end point was time to neutrophil engraftment. The treatment arms were well balanced and racially diverse. Median time to neutrophil engraftment was 12 days (95% confidence interval [CI], 10-14 days) for the omidubicel arm and 22 days (95% CI, 19-25 days) for the control arm (P < .001). The cumulative incidence of neutrophil engraftment was 96% for patients receiving omidubicel and 89% for patients receiving control transplants. The omidubicel arm had faster platelet recovery (55% vs 35% recovery by 42 days; P = .028), had a lower incidence of first grade 2 to 3 bacterial or invasive fungal infection (37% vs 57%; P = .027), and spent more time out of hospital during the first 100 days after transplant (median, 61 vs 48 days; P = .005) than controls. Differences in GVHD and survival between the 2 arms were not statistically significant. Transplantation with omidubicel results in faster hematopoietic recovery and reduces early transplant-related complications compared with standard UCBT. The results suggest that omidubicel may be considered as a new standard of care for adult patients eligible for UCBT. The trial was registered at www.clinicaltrials.gov as #NCT02730299.

Allogeneic Hematopoietic Cell Transplantation from Alternative Donors in Acute Myelogenous Leukemia: A Comparative Analysis

In the absence of HLA-matched related and unrelated donors, alternative donors must be found for patients in need of allogeneic hematopoietic cell transplantation (HCT). There are at least 3 donor options: a mismatched unrelated donor (MMUD), umbilical cord blood (UCB), and a haploidentical related donor (haplo); however, the optimal alternative donor type remains to be established. This study aimed to address how the outcomes of patients receiving these 3 alternative donor HCTs differ, and whether these outcomes change over time post-transplantation. We retrospectively analyzed Japanese nationwide transplantation registry data of adults with acute myelogenous leukemia (AML) undergoing allogeneic HCT while in first complete remission (CR) from an MMUD with a 7/8 match at the allele level (n = 601), with UCB (n = 1110), or from a haploidentical related donor (n = 221) between 2007 and 2018. For patients who underwent transplantation between 2007 and 2014, the 3-year overall survival (OS) for the MMUD, UCB, and Haplo groups was 60%, 54%, and 47%, respectively (P = .022). For those who underwent transplantation between 2015 and 2018, the 3-year OS in these groups was 60%, 66%, and 63%, respectively (P = .693). Multivariate analysis revealed that the risks of both overall mortality and nonrelapse mortality (NRM) were significantly lower in the later period than in the earlier period in the UCB group (hazard ratio [HR], 0.66 [P < .001] for OS; HR, 0.64 [P < .001] for NRM) and the Haplo group (HR, 0.58 [P = .019 for OS; HR, 0.39 [P = .004] for NRM), but not in the MMUD group (HR, 1.07 [P = .631] for OS; HR, 1.26 [P = .175] for NRM). The results of a test for interaction showed a significant difference in the effect of transplantation period on OS and NRM between the MMUD and UCB groups (P = .014 for OS; P = .004 for NRM) and between the MMUD and Haplo groups (P = .034 for OS; P = .003 for NRM). These findings demonstrate the recent improvements in the outcomes of UCB and Haplo transplantations in patients with AML in first CR that have resulted in a similar OS in patients undergoing HCT with grafts from MMUDs, UCB, and haploidentical donors in the later period of the study.

Real-world experience: Introduction of T cell replete haploidentical transplantations in a single center

Objectives

The aim of this study was to describe real-world data on outcomes of T cell replete haploidentical hematopoietic stem cell transplantation (HSCT) after the introduction of this modality in a single center and to compare them with different donor types.

Method

Outcomes of 30 consecutive patients with hematological malignancies that received T cell replete haploidentical HSCT with posttransplantation cyclophosphamide (PTCY) from 2016 to 2018 in our center were analyzed and compared to the outcome of human leukocyte antigen (HLA)-related and unrelated matched donor HSCT (n = 97) and to a historical cohort of T cell depleted haploidentical HSCT (n = 11).

Results

One year graft-versus-host-free, relapse-free survival in haploidentical HSCT was comparable with other donor types (haplo 40%, matched related donor [MRD] 33%, matched unrelated donor [MUD] 25%, p = 0.55). Non relapse mortality was high in haploidentical HSCT (50%), mostly due to infectious complications. However, relapse rates were only 3%, and OS and progression-free survival after 1 year were 47% and thereby also similar to HLA-matched HSCT in our center (MRD 53%, MUD 48%).

Conclusion

Our data show that T cell replete haploidentical HSCT has similar outcomes to HLA identical HSCT after introduction in our center. More strict adaptation on infection prevention was a crucial aspect of our learning curve. Overall, this type of transplantation is a feasible option when lacking an HLA-identical donor. This option has advantages over an unrelated donor as it brings less logistical challenges than MUD transplantations.

Inflammatory monocytes promote pre-engraftment syndrome and tocilizumab can therapeutically limit pathology in patients

Unrelated cord blood transplantation (UCBT) is an effective treatment for hematopoietic disorders. However, this attractive approach is frequently accompanied by pre-engraftment syndrome (PES), severe cases of PES are associated with enhanced mortality and morbidity, but the pathogenesis of PES remains unclear. Here we show that GM-CSF produced by cord blood-derived inflammatory monocytes drives PES pathology, and that monocytes are the main source of IL-6 during PES. Further, we report the outcome of a single arm, single-center clinical study of tocilizumab in the treatment of steroid-refractory severe PES patients (www.chictr.org.cn ChiCTR1800015472). The study met the primary outcome measure since none of the patients was nonrelapse death during the 100 days follow-up. The study also met key secondary outcomes measures of neutrophil engraftment and hematopoiesis. These findings offer a therapeutic strategy with which to tackle PES and improve nonrelapse mortality.

Pre-engraftment syndrome is a major consideration during clinical application of unrelated cord blood transfusion and monocytes represent a critical cell type in immune-pathogenesis. Here the authors further establish the role of monocytes and GM-CSF in pre-engraftment syndrome and show clinical administration of tocilizumab limits pathology in pre-engraftment syndrome pathology in patients.

Reduction of Graft-versus-Host-Disease in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) Mice by Cotransplantation of Syngeneic Human Umbilical Cord-Derived Mesenchymal Stromal Cells

Graft-versus-host disease (GVHD) is one of the major complications following hematopoietic stem cell transplantation, which remains the sole curative therapy for many malignant diseases of the hematopoietic system. The immunomodulatory potential of mesenchymal stromal cells (MSCs) to treat GVHD is currently being tested in various preclinical and clinical trials. Because the results of the preclinical and clinical trials on the use of MSCs to treat GVHD have not been consistent, we analyzed the potential beneficial effects of syngeneic versus allogenic treatment, culture expansion of MSCs, and various MSC cell doses and time points of MSC transplantation in a murine GVHD model. We established the murine GVHD model based on the transplantation of umbilical cord blood-derived hematopoietic stem cells (UC-HSCs) and used this model to assess the therapeutic potential of umbilical cord blood-derived MSCs (UC-MSCs). The use of HSC and MSC populations derived from the same donor allowed us to exclude third-party cells and test the UC-HSCs and UC-MSCs in a matched setting. Moreover, we were able to compare various doses, transplantation time points, and the influence of culture expansion of MSCs on the impact of treatment. This resulted in 16 different treatment groups. The most efficient setting for treatment of UC-HSC-induced GVHD reactions was based on the simultaneous administration of 1 × 10⁶ culture-expanded, syngeneically matched UC-MSCs. This therapy effectively reduced the number of CD8⁺ T cells in the blood, protected the mice from weight loss, and prolonged their survival until the end of observation period. Taken together, our data show beneficial effects of (1) syngeneic over allogeneic UC-HSCs and UC-MSCs, (2) culture-expanded cells over freshly isolated primary cells, (3) simultaneous over sequential administration, and (4) high doses of UC-MSCs. The animal model of GVHD established here is now available for more detailed studies, including a comparative analysis of the efficacy of MSCs derived from alternative sources, such as adipose tissue and bone marrow.

Perspectives on establishing a public cord blood inventory in South Africa

The South African population is highly diverse, both ethnically and genetically. This diversity is particularly true for the African ancestry and various mixed ancestry population groups. These groups are under-represented in national and international bone marrow and peripheral blood donor registries, making it challenging to identify HLA-matched and mismatched unrelated donors when patients from these groups require allogeneic hematopoietic stem and progenitor cell transplantation. In most high-income countries, banked cord blood (CB) units provide an attractive source of hematopoietic progenitor cells for genetically diverse populations. SA does not have a public CB inventory, leaving many patients without access to this important treatment modality. Haploidentical transplantation provides an alternative. In recent years, the use of post-transplant cyclophosphamide has significantly reduced the incidence of graft-versus-host disease after haploidentical transplantation and has improved transplantation outcomes. However, it is difficult to identify suitable haploidentical donors in SA because of family disruption and a high prevalence of HIV. Here the authors provide a brief historical overview of the ethnic and genetic diversity of the country and region. The authors provide a southern African perspective on HLA diversity, consider the allogeneic hematopoietic stem and progenitor cell transplantation landscape and explore the need to establish a public CB bank (CBB) in SA. The health policy and regulatory frameworks that will impact on a CBB in the country SA are also explored. Finally, the authors discuss several matters we believe require attention when considering the establishment of a sustainable public CBB in the South African context.

Single Cord Blood Transplantation Versus Unmanipulated Haploidentical Transplantation for Adults with Acute Myeloid Leukemia in Complete Remission

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative post-remission therapy for adult patients with acute myeloid leukemia (AML) in complete remission (CR). The availability of alternative human leukocyte antigen (HLA)-mismatched donors, such as cord blood and haploidentical related donors, could allow patients to receive allogeneic HCT who are without an HLA-matched sibling or unrelated donor. The use of these alternative donors is preferable for patients with advanced disease due to the rapid availability. However, comparative data for cord blood transplantation (CBT) and haploidentical related donor transplantation (haplo-HCT) are limited for adult patients with AML in CR. We sought to compare overall survival (OS); leukemia-free survival (LFS); graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS); and chronic GVHD-free, relapse-free survival (CRFS) between single-unit CBT (SCBT) and haplo-HCT recipients for adult patients with intermediate- or poor-risk AML in CR. We retrospectively analyzed and compared the results of allogeneic hematopoietic cell transplantation in 1313 adult patients with intermediate- or poor-risk AML in CR who received either SCBT (n = 1102) or unmanipulated haplo-HCT (n = 211) between 2007 and 2018 in Japan. Among the whole cohort, the cumulative incidences of neutrophil and platelet recovery were significantly lower in SCBT recipients compared with those in haplo-HCT recipients (P < .001 for neutrophil, P < .001 for platelet). SCBT was significantly associated with a higher incidence of grade II to IV acute GVHD and lower incidence of extensive chronic GVHD compared to haplo-HCT (P = .013 for grades II to IV acute GVHD; P = .006 for extensive chronic GVHD). Haplo-HCT recipients developed a higher incidence of cytomegalovirus (CMV) antigenemia compared to SCBT recipients (P = .004). In the multivariate analysis, there were no significant differences for grades III or IV acute GVHD (hazard ratio [HR], 1.17; 95% confidence interval [CI], .88 to 1.57; P = .26), relapse incidence (HR, 1.09; 95% CI, .76 to 1.58; P = .61), non-relapse mortality (HR, .83; 95% CI, .58 to 1.18; P = .32), OS (HR, .92; 95% CI, .70 to 1.20; P = .56), LFS (HR, .94; 95% CI, .73 to 1.21; P = .67), GRFS (HR, 1.12; 95% CI, .90 to 1.40; P = .27), or CRFS (HR, 1.15; 95% CI, .92 to 1.44; P = .19) between the two donor types. In the propensity score matching analysis, which identified 180 patients in each cohort, there were no significant differences in transplant outcomes between the two donor types, except for delayed neutrophil (P < .001) and platelet recovery (P < .001) and a higher incidence of grades II to IV acute GVHD (P = .052) in SCBT. SCBT and unmanipulated haplo-HCT had similar survival outcomes for adult patients with AML in CR despite the lower hematopoietic recovery and higher grade II to IV acute GVHD in SCBT recipients and the higher CMV antigenemia in haplo-HCT recipients.

Double unrelated umbilical cord blood vs HLA-haploidentical bone marrow transplantation: the BMT CTN 1101 trial

Results of 2 parallel phase 2 trials of transplantation of unrelated umbilical cord blood (UCB) or bone marrow (BM) from HLA-haploidentical relatives provided equipoise for direct comparison of these donor sources. Between June 2012 and June 2018, 368 patients aged 18 to 70 years with chemotherapy-sensitive lymphoma or acute leukemia in remission were randomly assigned to undergo UCB (n = 186) or haploidentical (n = 182) transplant. Reduced-intensity conditioning comprised total-body irradiation with cyclophosphamide and fludarabine for both donor types. Graft-versus-host disease prophylaxis for UCB transplantation was cyclosporine and mycophenolate mofetil (MMF) and for haploidentical transplantation, posttransplant cyclophosphamide, tacrolimus, and MMF. The primary end point was 2-year progression-free survival (PFS). Treatment groups had similar age, sex, self-reported ethnic origin, performance status, disease, and disease status at randomization. Two-year PFS was 35% (95% confidence interval [CI], 28% to 42%) compared with 41% (95% CI, 34% to 48%) after UCB and haploidentical transplants, respectively (P = .41). Prespecified analysis of secondary end points recorded higher 2-year nonrelapse mortality after UCB, 18% (95% CI, 13% to 24%), compared with haploidentical transplantation, 11% (95% CI, 6% to 16%), P = .04. This led to lower 2-year overall survival (OS) after UCB compared with haploidentical transplantation, 46% (95% CI, 38-53) and 57% (95% CI 49% to 64%), respectively (P = .04). The trial did not demonstrate a statistically significant difference in the primary end point, 2-year PFS, between the donor sources. Although both donor sources extend access to reduced-intensity transplantation, analyses of secondary end points, including OS, favor haploidentical BM donors. This trial was registered at www.clinicaltrials.gov as #NCT01597778.

History of hematopoietic cell transplantation: challenges and progress

After more than 60 years of research in allogeneic hematopoietic cell transplantation (HCT), this therapy has advanced from one that was declared dead in the 1960s to a standard treatment of otherwise fatal malignant and non-malignant blood diseases. To date, close to 1.5 million hematopoietic cell transplants have been performed in more than 1,500 transplantation centers worldwide. This review will highlight the enormous efforts by numerous investigators throughout the world who have brought the experimental field of HCT to clinical reality, examine ongoing challenges, and provide insights for the future.

Haploidentical Hematopoietic Stem Cell Transplantation Versus Umbilical Cord Blood Transplantation in Hematologic Malignancies: A Systematic Review and Meta-Analysis

Haploidentical hematopoietic stem cell transplantation (Haplo-SCT) and umbilical cord blood transplantation (UCBT) are two important alternatives when a matched sibling donor is unavailable. Several studies have reported inconsistent clinical outcomes comparing Haplo-SCT and UCBT. Therefore, it is necessary to synthesize the existing evidence regarding outcomes of stem cell transplantations comparing Haplo-SCT with UCBT. We searched article titles that compared transplantation with Haplo-SCT and UCBT in MEDLINE (PubMed), Cochrane library, and EMBASE database. To compare clinical outcomes between Haplo-SCT and UCBT, we performed a meta-analysis of 12 studies and reported the pooled odds ratios (ORs) of 6 end points including overall survival (OS), progression-free survival (PFS), nonrelapse mortality (NRM), relapse rate (RR), acute graft-versus-host disease (aGVHD), and chronic graft-versus-host disease (cGVHD). We found that Haplo-SCT was associated with a significantly superior OS (pooled OR of 0.74, 95% confidence interval [CI] 0.68 to 0.80) and PFS (0.77, 95% CI 0.72 to 0.83), as well as a lower NRM (0.72, 95% CI 0.64 to 0.80) and aGVHD (0.87, 95% CI 0.77 to 0.98) compared to the UCBT group. We also found a significantly increased risk of cGVHD in Haplo-SCT group (1.40, 95% CI 1.22 to 1.62). In terms of RR, Haplo-SCT was comparable to UCBT (0.91, 95% CI 0.79 to 1.05). Results of this meta-analysis demonstrate that Haplo-SCT results in better clinical outcomes compared to UCBT in terms of OS, PFS, TRM, and aGVHD, but is inferior to UCBT in terms of increased cGVHD risk. Further prospective comparisons between Haplo-SCT and UCBT are needed.

Evolution of the role of haploidentical stem cell transplantation: past, present, and future

INTRODUCTION

The accessibility to haplo-donors has led to an increase in the number of haplo-HSCT worldwide. A systematic search of the PubMed database between 2000 to present was performed.

AREAS COVERED

In this review, the authors discussed the most used approaches to perform haplo-HSCT and its results: T-cell depletion (TCD, including Perugia platform and its modifications) and T-cell repleted haplo (TCR, including the high-dose post-transplant cyclophosphamide strategy (Baltimore protocol) and the Beijing protocol). The improvements and modifications made to the different strategies have increased the indications of haplo-HSCT, including both malignant and nonmalignant disorders. Focusing on the Baltimore protocol, the authors review the results of the retrospective studies that have compared it to other donor transplants. The limitations of this strategy in terms of toxicity, graft complications, and GVHD are also discussed in detail. Finally, possible approaches to improve the outcomes of TCR haplo-HSCT are presented.

EXPERT OPINION

The recent advances in the field of haplo-HSCT have allowed a large number of patients with incurable diseases to benefit from this procedure despite not having a matched donor. With all available strategies, virtually no patient who needs an allogeneic transplant should be excluded by the absence of a donor.

Measurable residual disease of acute lymphoblastic leukemia in allograft settings: how to evaluate and intervene

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a curable strategy for acute lymphoblastic leukemia (ALL), especially for adult cases. However, leukemia relapse after allograft restricts the improvement of transplant outcomes. Measurable residual disease (MRD) has been the strongest predictor for relapse after allo-HSCT, allowing MRD-directed preemptive therapy.

AREAS COVERED

This manuscript summarizes the detection of MRD in patients with ALL who undergo allo-HSCT, focusing the effects of positive pre-HSCT MRD and post-HSCT MRD on outcomes as well as MRD-directed interventions.

EXPERT OPINION

Except for MFC and RQ-PCR, other strategies, such as next-generation sequencing and RNAseq, have been developed for MRD determination. Negative effects of positive MRD peri-transplantation on outcomes of ALL patients were observed both in human leukocyte antigen (HLA)-matched sibling donor transplantation and in alternative donor transplantation. Advances have been made in determining the need for transplant according to MRD evaluation after induction or consolidation therapy. A number of approaches, including CAR-T-cell therapy, antibodies (blinatumomab, etc), targeted therapy (imatinib, etc), transplant donor selection, as well as donor lymphocyte infusion and interferon-α, have been successfully used or are promising for peri-transplantation MRD interventions. This progress could lead to the significant improvement of transplant outcomes for ALL patients.

Uniform graft-versus-host disease prophylaxis with posttransplant cyclophosphamide, sirolimus, and mycophenolate mofetil following hematopoietic stem cell transplantation from haploidentical, matched sibling and unrelated donors

Following the success of posttransplant cyclophosphamide (PT-CY) as graft-versus-host disease (GVHD) prophylaxis in haploidentical transplantation, this prevention strategy has progressively been used for allogeneic hematopoietic stem cell transplantation (allo-HSCT) from HLA-matched sibling (MSD) and unrelated donor (MUD). We have introduced PT-CY plus sirolimus and micophenolate mofetil (PT-CY-Sir-MMF) as GVHD prophylaxis in allo-HSCT, irrespective of donor type. This study reports on the safety and efficacy of PT-CY-Sir-MMF in 158 consecutive allo-HSCT from MSD (n = 52), MUD (n = 64), and haploidentical (n = 42) donor. Median age was 53 years and 66% had acute leukemia or myelodysplastic syndrome. Cumulative incidences of acute GHVD grade II-IV, III-IV and moderate to severe cGVHD were 27%, 9% and 27%, respectively. The incidence of hepatic sinusoidal obstruction syndrome was 9.5%. The 1-year cumulative incidence of non-relapse mortality, relapse and event-free survival were 14%, 12% and 75%, respectively. Compared with MSD and MUD, haploidentical transplantation had a higher incidence of CMV DNAemia requiring therapy (34% vs 35% and 52%, respectively, p = 0.04) and was a risk factor for grade III-IV acute GVHD (RR 2.8, p = 0.05). Our study shows that PT-CY-Sir-MMF is not only feasible and effective in preventing GVHD after haploidentical HSCT, but also in allo-HSCT from MSD and MUD.