HLA-haploidentical vs matched-sibling hematopoietic cell transplantation: a systematic review and meta-analysis

Future directions in haploidentical hematopoietic stem cell transplantation

Outcomes of haploidentical hematopoietic stem cell transplantation (haplo-SCT) have improved over time. Graft failure and graft-versus-host disease (GVHD), which were important complications in major human leukocyte antigen (HLA)-disparity stem cell transplantation, have significantly decreased. These improvements have led to an exponential increase in the use of haploidentical donors for transplantation, as well as in the number of publications evaluating haplo-SCT outcomes. Many studies focused on factors important in donor selection, novel conditioning regimens or GVHD prophylaxis, the impact of donor-specific anti-HLA antibodies (DSA), as well as strategies to prevent disease relapse post-transplant. DSA represents an important limitation and multimodality desensitization protocols, including plasma exchange, rituximab, intravenous immunoglobulin and donor buffy coat infusion, can contribute to the successful engraftment in patients with high DSA levels and is currently the standard therapy for highly allosensitized individuals. With regards to donor selection, younger donors are preferred due to lower risk of complications and better transplant outcomes. Moreover, recent studies also showed that younger haploidentical donors may be a better choice than older-matched unrelated donors. Improvement of disease relapse remains a top priority, and several studies have demonstrated that higher natural killer (NK) cell numbers early post-transplant are associated with improved outcomes. Prospective studies have started to assess the role of NK cell administration in decreasing post-transplant relapse. These studies suggest that the incorporation of other cell products post-transplant, including the administration of chimeric antigen receptor T-cells, should be explored in the future.

ASTCT Consensus Recommendations on Testing and Treatment of Patients with Donor-specific Anti-HLA Antibodies

Donor-specific anti-HLA antibodies (DSA) are an important cause of engraftment failure and may negatively impact survival outcomes of patients receiving allogeneic hematopoietic stem cell transplantation (HSCT) using an HLA-mismatched allograft. The incidence of DSA varies across studies, depending on individual factors, detection or identification methods and thresholds considered clinically relevant. Although DSA testing by multiplex bead arrays remains semiquantitative, it has been widely adopted as a standard test in most transplant centers. Additional testing to determine risk of allograft rejection may include assays with HLA antigens in natural conformation, such as flow cytometric crossmatch, and/or antibody binding assays, such as C1q testing. Patients with low level of DSA (<2,000 mean fluorescence intensity; MFI) may not require treatment, while others with very high level of DSA (>20,000 MFI) may be at very high-risk for engraftment failure despite current therapies. By contrast, in patients with moderate or high level of DSA, desensitization therapy can successfully mitigate DSA levels and improve donor cell engraftment rate, with comparable outcomes to patients without DSA. Treatment is largely empirical and multimodal, involving the removal, neutralization, and blocking of antibodies, as well as inhibition of antibody production to prevent activation of the complement cascade. Desensitization protocols are based on accumulated multicenter experience, while prospective multicenter studies remain lacking. Most patients require a full intensity protocol that includes plasma exchange, while protocols relying only on rituximab and intravenous immunoglobulin may be sufficient for patients with lower DSA levels and negative C1q and/or flow cytometric crossmatch. Monitoring DSA levels before and after HSCT could guide preemptive treatment when high levels persist after stem cell infusion. This paper aims to standardize current evidence-based practice and formulate future directions to improve upon current knowledge and advance treatment for this relatively rare, but potentially serious complication in allogeneic HSCT recipients.

Novel MAGIC composite scores using both clinical symptoms and biomarkers best predict treatment outcomes of acute GVHD

ABSTRACT

Acute graft-versus-host disease (GVHD) grading systems that use only clinical symptoms at treatment initiation such as the Minnesota risk identify standard and high-risk categories but lack a low-risk category suitable to minimize immunosuppressive strategies. We developed a new grading system that includes a low-risk stratum based on clinical symptoms alone and determined whether the incorporation of biomarkers would improve the model's prognostic accuracy. We randomly divided 1863 patients in the Mount Sinai Acute GVHD International Consortium (MAGIC) who were treated for GVHD into training and validation cohorts. Patients in the training cohort were divided into 14 groups based on similarity of clinical symptoms and similar nonrelapse mortality (NRM); we used a classification and regression tree (CART) algorithm to create three Manhattan risk groups that produced a significantly higher area under the receiver operating characteristic curve (AUC) for 6-month NRM than the Minnesota risk classification (0.69 vs 0.64, P = .009) in the validation cohort. We integrated serum GVHD biomarker scores with Manhattan risk using patients with available serum samples and again used a CART algorithm to establish 3 MAGIC composite scores that significantly improved prediction of NRM compared to Manhattan risk (AUC, 0.76 vs 0.70, P = .010). Each increase in MAGIC composite score also corresponded to a significant decrease in day 28 treatment response (80% vs 63% vs 30%, P < .001). We conclude that the MAGIC composite score more accurately predicts response to therapy and long-term outcomes than systems based on clinical symptoms alone and may help guide clinical decisions and trial design.

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

ABSTRACT

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

Allogeneic hematopoietic cell transplantation from alternative donors in acute myeloid leukemia

Allogeneic hematopoietic cell transplantation (HCT) potentially provides a cure for patients with acute myeloid leukemia (AML) who are unlikely to be cured with chemotherapy alone. Previously, human leukocyte antigen (HLA)-matched related donors were used exclusively, which made the procedure available for a limited proportion of patients. The introduction of high-resolution HLA-typing technology, innovations in immunosuppressive therapy, and improved supportive care measures have significantly changed the situation. Now, patients without a matched related donor have an ample opportunity to receive allogeneic HCT with the use of matched or mismatched unrelated donors, umbilical cord blood grafts, or haploidentical related donors. The outcomes of alternative donor transplantations have improved over the past decades, and the growth of unrelated donor registries as well as the donor diversification have enhanced the chance of finding a suitable donor. With multiple alternative donor choices available for most patients, the donor selection is becoming increasingly important. To discuss the optimal donor choice in case of unavailability of an HLA-matched related donor, this article reviews the existing literature of retrospective and prospective comparisons of different alternative donor transplantations in AML and discusses the current state-of-art modalities in allogeneic HCT using alternative donors.

Outcomes of Human Leukocyte Antigen-Matched Related Donor and Haploidentical Allogeneic Hematopoietic Cell Transplantation Recipients by Immune Profiles of Recipients and Donors

Haploidentical (Haplo) allogeneic HCTs (alloHCT) have been used more frequently over the last decade as survival is similar to HLA-matched related donor (MRD) alloHCTs. We aimed to identify donor and recipient immune signatures before alloHCT that are associated with clinically meaningful outcomes in MRD vs Haplo alloHCT recipients. This retrospective cohort study of 165 MRD (n = 132) and Haplo (n = 33) alloHCT recipients and their related donors between 2007-2019 with paired peripheral blood samples immunophenotyped for T-cell, B-cell, NK cell and dendritic cell (DC) subsets. Immune cells were quantified before alloHCT in donors and recipients; calculations of immune cell ratios were classified as high, intermediate, and low and analyzed with alloHCT outcomes. Haplo donors were younger than MRD donors (median: 35 vs 51 years), whereas Haplo recipients were older than MRD recipients (median: 68 vs 54 years), were more likely to have a Karnofsky Performance Score ≤ 70 (76% vs 57%), 3+ comorbidities (54% vs 47%), and were in complete remission prior to alloHCT (58% vs 42%). In MRD alloHCT, a lower ratio of CD4+ to CD8+ effector memory cells in the donor was associated with lower 4-yr overall survival (OS; 25% vs 61%; P = .009), lower 4-yr progression free survival (PFS; 25% vs 58%; P = .014) and higher incidence of 1-yr transplant-related mortality (TRM; 39% vs 7%; P = .009) in recipients. A higher ratio of CD8+ effector memory to total NK cells measured in MRD recipients was associated with a higher incidence of grade II-IV aGvHD (63% vs 37%; P = .004) but was not statistically significant for III-IV aGvHD (23% vs 12%). In Haplo alloHCT, a lower ratio of total T-regulatory to CD4+ central memory cells in the donor was associated with lower 4-yr PFS (22% vs 60%; P = .0091). A higher ratio of CD4+ effector memory to CD8+ effector memory cells measured in Haplo recipients pre-alloHCT was associated with lower 4-yr OS (25% vs 88%; P = .0039). In both MRD and Haplo recipients, a higher ratio of CD4+ naïve to CD4+ central memory cells was associated with a higher incidence of grade II-IV aGvHD (64% vs 38%; P = .04). Evaluation of pre-alloHCT immune signatures of the donor and recipient may influence clinically meaningful patient outcomes in both MRD and Haplo transplants.

The health risk of social disadvantage is transplantable into a new host

Low socioeconomic status (SES) is a risk factor for mortality and immune dysfunction across a wide range of diseases, including cancer. However, cancer is distinct in the use of allogeneic hematopoietic cell transplantation (HCT) as a treatment for hematologic malignancies to transfer healthy hematopoietic cells from one person to another. This raises the question of whether social disadvantage of an HCT cell donor, as assessed by low SES, might impact the subsequent health outcomes of the HCT recipient. To evaluate the cellular transplantability of SES-associated health risk, we analyzed the health outcomes of 2,005 HCT recipients who were transplanted for hematologic malignancy at 125 United States transplant centers and tested whether their outcomes differed as a function of their cell donor's SES (controlling for other known HCT-related risk factors). Recipients transplanted with cells from donors in the lowest quartile of SES experienced a 9.7% reduction in overall survival (P = 0.001) and 6.6% increase in treatment-related mortality within 3 y (P = 0.008) compared to those transplanted from donors in the highest SES quartile. These results are consistent with previous research linking socioeconomic disadvantage to altered immune cell function and hematopoiesis, and they reveal an unanticipated persistence of those effects after cells are transferred into a new host environment. These SES-related disparities in health outcomes underscore the need to map the biological mechanisms involved in the social determinants of health and develop interventions to block those effects and enhance the health of both HCT donors and recipients.

Graft-versus-tumor effect of post-transplant cyclophosphamide-based allogeneic hematopoietic cell transplantation

Post-transplant cyclophosphamide (PTCy) is becoming the standard prophylaxis for graft-versus-host disease (GVHD) in HLA-haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) and in HLA-matched allo-HCT. Immune reconstitution in the post-transplant setting may influence the graft-versus-tumor (GVT) effect because PTCy has a profound effect on T cell and natural killer cell functions and their reconstitution after allo-HCT. However, many recent studies have shown that the incidence of relapse after allo-HCT with PTCy is comparable to that after conventional allo-HCT. To further improve the outcomes, it is critical to establish a strategy to maintain or effectively induce the GVT effect when using PTCy as a platform for GVHD prophylaxis. However, there is a paucity of studies focusing on the GVT effect in allo-HCT with PTCy. Therefore, focusing on this issue may lead to the establishment of more appropriate strategies to improve transplantation outcomes without exacerbating GVHD, including novel therapies involving cell modification.

Immune reconstitution in children after haploidentical haematopoietic stem cell transplantation

INTRODUCTION

Immune reconstitution (IR) kinetics of paediatric patients underwent haploidentical haematopoietic stem cell transplantation (HSCT) with post-transplant cyclophosphamide (PTCy) have not been extensively studied. We compared IR patterns of children receiving HSCT from haploidentical (n = 92) and HLA-matched donors (n = 36), and analysed risk factors for viral infection in these patients.

METHODS

We prospectively measured lymphocyte subset numbers before HSCT and at 1, 3, 6 and 12 months after HSCT. Blood cytomegalovirus (CMV), Epstein-Barr virus, adenovirus, BK virus (BKV) and urine adenovirus and BKV viral loads were measured at designated time points.

RESULTS

The median numbers of total T and T helper cells at 1 month were significantly lower in the haploidentical group compared with the HLA-matched group. Haploidentical HSCT recipients had significantly lower median numbers of several T cell subsets and B cells for 1 year after HSCT. The median NK cell count of the haploidentical group was lower at 1 month. BKV haemorrhagic cystitis, blood CMV and urine adenovirus reactivation were more frequently found in the haploidentical group. Post-haploidentical HSCT patients receiving anti-T lymphocyte globulin (ATG) had significantly lower median numbers of total T cells (at 1 month) and T helper cells (at 6 and 12 months) and higher rate of blood BKV reactivation compared with those without ATG.

CONCLUSION

Paediatric patients who undergo haploidentical HSCT with PTCy are likely to have delayed IR and an increased risk of viral reactivation/infection compared with HLA-matched HSCT. The addition of ATG to PTCy delayed T cell recovery and increased risk of BKV reactivation.

Allogenic hematopoietic stem cell transplantation outcomes of patients aged ≥ 55 years with acute myeloid leukemia or myelodysplastic syndromes in China: a retrospective study

BACKGROUND

Elderly patients with acute myeloid leukemia or myelodysplastic syndromes (AML/MDS) have historically had poor prognoses. However, there has been a recent increase in the use of allogenic hematopoietic stem cell transplantation (allo-HSCT) are in this patient population. Nevertheless, the optimal choice of donor type for the patients remains an unmet need. Limited data exist on the use of allo-HSCT in elderly patients with AML/MDS from China. To better understand and optimize the selection of donor type for the elderly patients, particularly for those with refractory or relapsed disease, in comparison with the previous studies in the US and Europe.

METHODS

Our retrospective study enrolled 259 patients aged over 55 years who underwent their first allo-HSCT between April 2015 and August 2022. These patients were divided into three groups based on donor type: haploidentical related donor group (haploidentical related donor transplantation [HID], n = 184), matched sibling donor group (matched sibling donor transplantation [MSD], n = 39), and matched unrelated donor group (matched unrelated donor transplantation [MUD], n = 36). Statistics were performed with the chi-square test, the log-rank and Fine-Gray tests.

RESULTS

The median age of the cohort was 57 years (range: 55-75) and 26.25% of patients were over 60 years old. Younger patients had a higher incidence of acute graft-versus-host disease (HR = 1.942, P = 0.035), faster neutrophil recovery (HR = 1.387, P = 0.012), and better overall survival (HR = 0.567, P = 0.043) than patients aged ≥ 60 years across the entire cohort. Patients with refractory or relapsed (R/R) diseases had delayed neutrophil engraftment (P = 0.010, HR = 0.752) and platelet engraftment (P < 0.001, HR = 0.596), higher incidence of relapses (HR = 2.300, P = 0.013), and inferior relapse-free survival (RFS) (HR = 1.740, HR = 0.016) regardless of donor type. When it came to graft-versus-host-disease-free, relapse-free survival (GRFS), MUDs turned out to be superior to HIDs (HR = 0.472, P = 0.026) according to the multivariable analysis. In contrast, we found MSDs had an inferior GRFS to HIDs in parallel (HR = 1.621, P = 0.043).

CONCLUSION

The choice of donor type did not significantly affect the outcomes of allo-HSCT. However, when considering the quality of post-transplant life, MUDs or HIDs from younger donors may be the optimal choice for elderly patients.

Effect of graft-versus-host disease on outcomes of HLA-haploidentical peripheral blood transplantation using post-transplant cyclophophamide

There is limited evidence regarding the association between graft-versus-host disease (GVHD) and reduced relapse in patients who undergo allogeneic hematopoietic stem cell transplantation from haploidentical donors (haplo-HSCT) using post-transplant cyclophosphamide (PTCY). We investigated the association between GVHD and transplant outcomes in 938 patients who received haplo-HSCT using PTCY. Overall survival (OS), relapse rate, and non-relapse mortality (NRM) were evaluated using landmark analysis at the landmark points at 100 and 360 days after HSCT for acute and chronic GVHD, respectively. Grade I-II acute GVHD was not associated with OS (adjusted hazard ratio: 1.15, 95% confidence interval: 0.85-1.57), relapse (1.03, 0.74-1.45) and NRM (1.15, 0.74-1.77). Conversely, grade III-IV acute GVHD was associated with higher NRM (3.16, 1.61-6.19), but no other outcomes. Limited chronic GVHD was not associated with OS (1.11, 0.48-1.95), relapse (1.05, 0.30-3.75) and NRM (1.30, 0.45-3.79). Extensive chronic GVHD was associated with higher NRM (2.40, 1.03-5.57), but no other outcome. In conclusion, any GVHD was not associated with a reduced relapse rate and improved OS, and Grade III-IV acute GVHD and extensive chronic GVHD were associated with higher NRM in patients who received haplo-HSCT using PTCY.

Relapse after allogeneic transplantation with post-transplant cyclophosphamide: Shattering myths and evolving insight

Early studies in allogeneic blood or marrow transplantation (alloBMT) demonstrated that HLA-mismatching was protective again relapse. However, benefits in relapse reduction were outweighed by a high risk of graft-versus-host disease (GVHD) when using conventional pharmacological immunosuppression. Post-transplant cyclophosphamide(PTCy)-based platforms abated the risk of GVHD thereby overcoming the negative effects of HLA-mismatching on survival. However, since its inception, PTCy has been shadowed by a reputation for a greater risk of relapse when compared with traditional GVHD prophylaxis. Specifically, whether PTCy reduces the anti-tumor efficacy of HLA-mismatched alloBMT by killing alloreactive T cells has been the subject of debate since the early 2000's. Here we review the many studies demonstrating the potent graft-versus-malignancy (GVM) properties of alloBMT with PTCy. We discuss the laboratory data from PTCy platforms supporting that T regulatory cells may be a major mechanism of prevention of GVHD and that natural killer (NK) cells may be early effectors of GVM. Finally, we propose potential paths to optimize GVM through selecting for class II mismatching and augmenting NK cell activity.

PTCY-Based Haploidentical Donor Transplantation versus HLA-Matched Related and Unrelated Donor Transplantations in Patients with Refractory or Relapsed Lymphoma-A Matched-Pair Analysis

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has demonstrated its potential as a curative option for patients with r/r lymphoma. With the introduction of post-transplant cyclophosphamide-based (PTCY) graft-versus-host disease (GvHD) prophylaxis, allo-HCT using haploidentical related donors (Haplo-HSCT) has emerged as a valuable alternative for patients without an available HLA-matched donor. In this study, we compared intermediate and long-term outcomes between Haplo-HSCT and HLA-matched related donor (MRD) and unrelated donor (URD) transplantations in 16 matched pairs using age, disease status, lymphoma classification and performance status as matching criteria. Of note, 88% of patients in each group presented with active disease at the time of conditioning. After a median follow-up of >10 years, 10-year overall and progression-free survival and non-relapse mortality incidence after Haplo-HSCT were 31%, 25% and 38%, respectively, and did not differ compared to the values observed in MRD-HSCT and URD-HSCT. A remarkable lower incidence of acute GvHD ≥ II and moderate and severe chronic GvHD was observed after Haplo-HSCT compared to MRD-HSCT (50%/50%, p = 0.03/0.03) and URD-HSCT (44%/38%, p = 0.04/0.08), resulting in slightly higher 10-year GvHD-free and relapse-free survival (25%) and chronic GvHD-free and relapse-free survival (25%) in the Haplo-HSCT group. In conclusion, Haplo-HSCT is an effective treatment in patients with non-remission NHL. Given its advantage of immediate availability, haploidentical donors should be preferably used in patients with progressive disease lacking an HLA-matched related donor.

Meta-analysis of the results of haploidentical transplantation in the treatment of aplastic anemia

This meta-analysis was to evaluate the outcome of haploidentical hematopoietic stem cell transplantation (Haplo-HSCT) for aplastic anemia (AA) compared with matched related donor (MRD)-HSCT, matched unrelated donor (MUD)-HSCT, and immunosuppressive therapy (IST). Pubmed, Embase, Cochrane Library, Web of Science, CNKI, WanFang, and VIP databases were searched for relevant studies from inception to 22 June 2022. Relative risk (RR) was used to indicate the effect indicator, with a 95% confidence interval (CI) being applied to express the effect size. A subgroup analysis based on the literature quality (low, fair, and high) was applied. Totally, 25 studies were included in this study, comprising 2252 patients. Our findings demonstrated no difference between Haplo-HSCT and MRD-HSCT in 1-, 2-, and 3-year overall survival (OS), failure-free survival (FFS), and engraftment. However, Haplo-HSCT had higher incidences of II-IV acute graft-versus-host disease (aGVHD), chronic GVHD (cGVHD), and cytomegalovirus infection. There were no differences in 3- and 5-year OS, 3-year FFS, platelet engraftment, graft failure (GF), II-IV grade of aGVHD, and complication between Haplo-HSCT and MUD-HSCT; however, Haplo-HSCT had a lower incidence of cGVHD. Compared with IST, Haplo-HSCT had a higher 3-year FFS and 3- and 6-month response rate. However, there were no differences in 3- and 5-year OS, and 12-month response rate between Haplo-HSCT and IST. This study suggests that Haplo-HSCT may be a realistic therapeutic option for AA, which may provide a reference for decision-making.

Efficacy of letermovir in HLA-haploidentical hematopoietic transplantation with posttransplant cyclophosphamide

BACKGROUND

Cytomegalovirus reactivation (CMV-R) is a significant complication of allogeneic hematopoietic stem cell transplantation (allo-HCT), especially in human leukocyte antigen-haploidentical transplantation (haplo-HCT) with posttransplant cyclophosphamide (PTCy). Prophylactic letermovir (LTV) prevents CMV-R in patients undergoing allo-HCT. However, evidence regarding its use in haplo-HCTs with PTCy is limited. Therefore, we aimed to investigate the efficacy of prophylactic LTV in haplo-HCT with PTCy.

METHODS

We retrospectively analyzed 52 patients seropositive for CMV who underwent haplo-HCT with PTCy at our institution between January 2015 and June 2021 and compared patients who received LTV prophylaxis (LTV group: n = 29) with those who did not receive prophylaxis for CMV (control group: n = 23). The primary endpoint was the 100-day cumulative CMV-R incidence. We used Gray's test and the Fine and Gray test to compare the two groups.

RESULTS

The 100-day cumulative CMV-R incidence was lower in the LTV group than in the control group (17.2% vs 81.8%, p < 0.001). Multivariate analysis revealed that prophylactic LTV reduced the 100-day cumulative CMV-R incidence (hazard ratio: 0.17, 95% confidence interval: 0.06-0.44, p < 0.001).

CONCLUSIONS

Prophylactic LTV effectively prevents CMV-R in patients undergoing haplo-HCT for PTCy.

GVHD relapse-free survival after peripheral blood hematopoietic cell transplantation for hematologic malignancies

The preferred choice for hematopoietic cell transplantation (HCT) donors in India is a matched related donor (MRD) followed by a haploidentical (haplo) donor for patients with hematological malignancies. International data in the haplo-HCT setting is mainly using bone marrow as a source. Almost all HCTs in India use peripheral blood stem cells (PBSC), which increases the risk of graft-versus-host disease (GVHD). In this single-center prospective study from 2017 to 2021, we sought to compare these outcomes prospectively in adult patients with hematological malignancies. Patient, disease, donor, and HCT details were prospectively recorded. GVHD prophylaxis included cyclosporine + methotrexate in MRD-HCT and post-transplant cyclophosphamide (PTCy) based in haplo-HCT. The primary endpoint GVHD relapse-free survival (GRFS) was defined as the time post-HCT without any of the following events: grade III-IV acute GVHD, chronic GVHD requiring systemic immunosuppressive treatment, disease relapse, or death from any cause. A total of 41 MRD and 33 haplo-HCT recipients were included in the study. Both cohorts were matched for age, sex, diagnosis, disease risk index, donor age, sex and CMV mismatches, and CD34 counts. A lower proportion of MRD-HCT recipients than haplo-HCT received myeloablative conditioning (39% vs. 76%, p = 0.002). There was no difference in the cumulative incidence of grade III-IV acute GVHD (16% vs. 27%, p = 0.2) or moderate-to-severe chronic GVHD (58% vs. 71%, p = 0.5). The one-year GRFS was not significantly different (53% vs. 38%, p = 0.2), with median GRFS of 420 and 274 days. The relapse incidence (22% vs. 19%, p = 0.6) and non-relapse mortality (25% vs. 35%, p = 0.4) did not differ. There was no difference in overall survival at one year (60% vs. 52%, p = 0.3). Despite a higher proportion of myeloablative conditioning in the haplo-HCT cohort, all outcomes, including GRFS, were comparable to those of the MRD-HCT cohort. This should encourage patients without an MRD to undergo haplo-HCT.

Allogeneic haematopoietic cell transplants as dynamical systems: influence of early-term immune milieu on long-term T-cell recovery

Objectives

Immune recovery following haematopoietic cell transplantation (HCT) functions as a dynamical system. Reducing the duration of intense immune suppression and augmenting antigen presentation has the potential to optimise T-cell reconstitution, potentially influencing long-term outcomes.

Methods

Based on donor-derived T-cell recovery, 26 patients were adaptively randomised between mycophenolate mofetil (MMF) administered for 30-day post-transplant with filgrastim for cytokine support (MMF30 arm, N = 11), or MMF given for 15 days with sargramostim (MMF15 arm, N = 15). All patients underwent in vivo T-cell depletion with 5.1 mg kg^-1 antithymocyte globulin (administered over 3 days, Day -9 through to Day -7) and received reduced intensity 450 cGy total body irradiation (3 fractions on Day -1 and Day 0). Patients underwent HLA-matched related and unrelated donor haematopoietic cell transplantation (HCT).

Results

Clinical outcomes were equivalent between the two groups. The MMF15 arm demonstrated superior T-cell, as well as T-cell subset recovery and a trend towards superior T-cell receptor (TCR) diversity in the first month with this difference persisting through the first year. T-cell repertoire recovery was more rapid and sustained, as well as more diverse in the MMF15 arm.

Conclusion

The long-term superior immune recovery in the MMF15 arm, administered GMCSF, is consistent with a disproportionate impact of early interventions in HCT. Modifying the 'immune-milieu' following allogeneic HCT is feasible and may influence long-term T-cell recovery.

Association of β₂ microglobulin level and glomerular filtration rate in patients with acute leukemia after hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation is a life-saving therapy in patients suffering from acute leukemia. However, kidney complications developed after performing hematopoietic stem cell transplantation can affect the course and prognosis of the disease in patients with acute leukemia. This study is aimed at assessing the functional status of the kidneys in patients with acute leukemia who have undergone hematopoietic stem cell transplantation. The study has observed a group of patients with acute lymphoblastic leukemia and acute myeloid leukemia who have undergone hematopoietic stem cell transplantation. It has been discovered that β2 microglobulin is a sensitive method of analyzing renal function, with the β2 microglobulin threshold urine level not exceeding 0.3 mg/L. The complex diagnostics of kidney function in hematopoietic stem cell transplantation recipients has given the opportunity to identify the relationship between increased β2 microglobulin levels and decreased glomerular filtration rate. It has been determined that β2 microglobulin is a biomarker of renal disorders. The obtained data have showed that β2 microglobulin can be used as a diagnostic marker of reduced kidney function.

How I prevent GVHD in high-risk patients: posttransplant cyclophosphamide and beyond

Advances in conditioning, graft-versus-host disease (GVHD) prophylaxis and antimicrobial prophylaxis have improved the safety of allogeneic hematopoietic cell transplantation (HCT), leading to a substantial increase in the number of patients transplanted each year. This influx of patients along with progress in remission-inducing and posttransplant maintenance strategies for hematologic malignancies has led to new GVHD risk factors and high-risk groups: HLA-mismatched related (haplo) and unrelated (MMUD) donors; older recipient age; posttransplant maintenance; prior checkpoint inhibitor and autologous HCT exposure; and patients with benign hematologic disorders. Along with the changing transplant population, the field of HCT has dramatically shifted in the past decade because of the widespread adoption of posttransplantation cyclophosphamide (PTCy), which has increased the use of HLA-mismatched related donors to levels comparable to HLA-matched related donors. Its success has led investigators to explore PTCy's utility for HLA-matched HCT, where we predict it will be embraced as well. Additionally, combinations of promising new agents for GVHD prophylaxis such as abatacept and JAK inhibitors with PTCy inspire hope for an even safer transplant platform. Using 3 illustrative cases, we review our current approach to transplantation of patients at high risk of GVHD using our modern armamentarium.

Mild Acute Graft-Versus-Host Disease Improves Outcomes After HLA-Haploidentical-Related Donor Transplantation Using Posttransplant Cyclophosphamide and Cord Blood Transplantation

Haploidentical-related donor transplantation using posttransplant cyclophosphamide (PTCy-haplo) and cord blood transplantation (CBT) are valid alternatives for patients with hematological malignancies when HLA-matched donor transplantation (MDT) is unavailable. However, the effects of graft-versus-host disease (GVHD) on outcomes after these transplants have not been fully elucidated. Therefore, we evaluated the effects of acute and chronic GVHD on transplant outcomes after PTCy-haplo transplants and compared them with CBT and MDT. We included a total of 914 adult patients with hematological malignancies in the Kyoto Stem Cell Transplantation Group registry who received PTCy-haplo (N = 120), CBT (N = 402), and MDT (N = 392), and achieved neutrophil engraftment. A multivariate analysis revealed that grade I-II acute GVHD improved of overall survival (OS) after PTCy-haplo [hazard ratio (HR) = 0.39, P = 0.018] and CBT (HR = 0.48, P < 0.001), but not after MDT (HR = 0.80, P = 0.267) compared with patients without acute GVHD. Grade I-II acute GVHD had a trend toward reducing the risk of nonrelapse mortality (NRM) after PTCy-haplo (HR = 0.13, P = 0.060) and this positive effect was significant after CBT (HR = 0.39, P = 0.003). A negative impact of grade III-IV acute GVHD on NRM was observed after CBT and MDT, but not after PTCy-haplo. Limited chronic GVHD had a positive impact on OS after CBT and MDT, but not after PTCy-haplo. In conclusion, mild acute GVHD improved outcomes after PTCy-haplo and CBT, and limited chronic GVHD improved outcomes after CBT and MDT. These data indicated that the effects of GVHD on transplant outcomes depended on transplant platforms.

Case report: First report of haploidentical allogeneic hematopoietic stem cell transplantation from donors with mild alpha-thalassemia for acute leukemia

For acute leukemia (AL) with adverse prognostic factors, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the standard care option after the first complete remission. Meanwhile, as the success of haploidentical HSCT (haplo-HSCT), haploidentical donors (HIDs) become a reliable choice. However, there have been no reports on haplo-HSCT from HIDs with mild alpha(α)-thalassemia for AL yet. In the present report, we first describe two cases of successful haplo-HSCT from HIDs with mild α-thalassemia for AL.

Systematic overview of HLA-matched allogeneic hematopoietic cell transplantation with post-transplantation cyclophosphamide

The successful application of post-transplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis in HLA-haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) led to the expansion of its application to HLA-matched related and unrelated allo-HCT. Notably, single-agent PTCy was found to be feasible for GVHD prevention in HLA-matched bone marrow transplantation. Single-agent PTCy prophylaxis was later attempted to control GVHD in HLA-matched peripheral blood stem cell transplantation (PBSCT), but this approach was inadequate to alleviate GVHD as evidenced by the high incidence of severe GVHD and/or non-relapse mortality. Therefore, various combinations of immunosuppressants with PTCy have been explored to identify the optimal drug combination that would efficiently prevent GVHD in HLA-matched PBSCT. A recent murine study helped clarify the putative mechanism underlying the activity of PTCy, demonstrating that PTCy impairs the proliferation and function of alloreactive T cells from the donor, but does not eliminate alloreactive T cells altogether. In addition, imbalanced reconstitution of NK cell as well as T cells has been observed in HLA-haploidentical allo-HCT. Therefore, it remains unclear whether or not PTCy-containing GVHD prophylaxis should replace the classical GVHD prophylaxis regimen in the HLA-matched setting, and convincing evidence supporting the benefits of PTCy is needed.

Donor specific HLA antibody in hematopoietic stem cell transplantation: Implications for donor selection

Advances in hematopoietic stem cell transplant (HSCT) have led to changes in the approach to donor selection. Many of these new approaches result in greater HLA loci mismatching, either through the selection of haploidentical donors or permissive HLA mismatches. Although these approaches increase the potential of transplant for many patients by expanding the number of acceptable donor HLA genotypes, they add the potential barrier of donor-specific HLA antibodies (DSA). DSA presents a unique challenge in HSCT, as it can limit engraftment and lead to graft failure. However, transient reduction of HLA antibodies through desensitization treatments can limit the risk of graft failure and facilitate engraftment. Thus, the consideration of DSA in donor selection and the management of DSA prior to transplant are playing an increasingly important role in HSCT. In this review, we will discuss studies addressing the role of HLA antibodies in HSCT, the reported impact of desensitization on DSA levels, and the implications for selecting donors for patients with DSA. We found that there is a clear consensus that moderate strength DSA should be avoided, while desensitization strategies are reported to be effective in most cases at reducing DSA to amenable levels. There is limited information regarding the impact of specific characteristics of DSA, such as HLA loci or overall level of sensitization, which could further aid in donor selection for sensitized HSCT candidates.

Evaluation of Kidneys’ Functional State in Acute Lymphoblastic Leukemia Patients Following Hematopoietic Stem Cell Transplantation

BACKGROUND: Hematopoietic Stem Cell Transplantation (HSCT) has recently been a widely used method of therapy in various fields of current medicine, particularly in hematology.Some patients develop renal disorders following HSCT. AIM: This study aims to evaluate the dynamics of changes in the functional state of the kidneys in patients with ALL after HSCT. METHODS: In the period from 2015 to 2021, for the first time in Kazakhstan, patients with acute lymphoblastic leukemia (ALL) who underwent allogeneic and haploidentical HSCT were prospectively examined. RESULTS: We determined that the greatest decrease in glomerular filtration rate occurred in the group of patients who underwent haploidentical bone marrow transplantation. Moreover, we believe that our results are related to known contributing risk factors, such as the type of performed transplantation and the duration of taking medications for the prevention of graft versus host disease. Our results also indicate that the lethal outcome in the group with haploidentical HSCT in the studied patients with ALL was greater than in the group with allogeneic HSCT. CONCLUSION: In conclusion, a decrease in kidney function in patients who have survived HSCT is probably a common complication; however, further prospective studies are required to confirm these results to develop additional algorithms for the treatment and prevention of renal disorders in patients with acute leukemia after HSCT.

A Prospective Study of an HLA-Haploidentical Peripheral Blood Stem Cell Transplantation Regimen Based on Modification of the Dose of Posttransplant Cyclophosphamide for Poor Prognosis or Refractory Hematological Malignancies

The optimal dose of posttransplant cyclophosphamide (PTCy) for use in patients undergoing HLA-haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide (PTCy-haplo) has not been sufficiently examined. This study evaluates the safety and efficacy of HLA-haploidentical hematopoietic cell transplantation with a reduced dose of PTCy for patients with a poor prognosis or those with refractory hematological malignancies. We conducted a prospective clinical study of PTCy-haplo with peripheral blood stem cells (PBSCs) using a modified PTCy dosage regimen consisting of 50 mg/kg on day 3 posttransplantation and a reduced dose of 25 mg/kg on day 4. The cumulative incidences of grades II to III and IV acute graft-versus-host disease (GVHD) at day 100 posttransplantation were 30% and 0%, respectively. The cumulative incidence of moderate-to-severe chronic GVHD after transplantation was 7.0%. The cumulative incidence of nonrelapse mortality at 1 year posttransplantation was 6.1%. Overall survival (OS) at 1 year was 66%. In addition, the restricted cubic-spline Cox regression analysis showed nonlinear relationship between the number of infused CD34⁺ cells and CD3⁺ cells, and OS. A graft composition of >4.54 × 10⁶/kg CD34⁺ cells and >1.85 × 10⁸/kg but ≤3.70 × 10⁸/kg CD3⁺ cells was significantly associated with better survival, irrespective of the disease status (hazard ratio, 0.13; 95% confidence interval, 0.04–0.41; P < 0.001). These results suggest that PTCy-haplo with PBSCs using a de-escalated dose of 50 mg/kg on day 3 and 25 mg/kg on day 4 posttransplantation is a feasible option.

A phase II study of post-transplant cyclophosphamide combined with tacrolimus for GVHD prophylaxis after HLA-matched related/unrelated allogeneic hematopoietic stem cell transplantation

A combination of three post-transplant drugs, cyclophosphamide (PTCy), a calcineurin inhibitor, and mycophenolate mofetil, has long been used for prophylaxis of graft-versus-host-disease (GVHD) after HLA-haploidentical allogeneic hematopoietic cell transplantation (allo-HCT). Recently, this combination has been used following HLA-matched allo-HCT as well, but the optimal combination of drugs for GVHD prophylaxis in an HLA-matched setting remains unclear. This prospective phase II study evaluated the safety and efficacy of PTCy plus tacrolimus (TAC) for GVHD prophylaxis after allo-HCT from HLA-matched related donors (MRD) or HLA-matched unrelated donors (MUD). The cumulative incidences of grades II-IV and III-IV acute GVHD at 100 days post-transplantation were 18% and 5.9%, respectively, in the MRD group, and 18% and 9.1%, respectively, in the MUD group. The cumulative incidences of moderate to severe chronic GVHD at 1 year were 12% and 9.1% in the MRD and MUD groups, respectively. The 1-year overall survival rates in the MRD and MUD groups were 88% and 64%, respectively, and the 1-year GVHD-free, relapse free survival rates were 59% and 50%, respectively. These results suggest that GVHD prophylaxis with a less intensive double drug combination (PT/Cy and TAC) might be feasible after HLA-matched allo-HCT.Clinical Trial Notation This trial was a prospective single-center trial registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR; identification number: UMIN000023890) and the Japan Registry of Clinical Trials (jRCTs051180143).

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.

Hematopoietic Cell Transplantation, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology

Hematopoietic cell transplantation (HCT) involves the infusion of hematopoietic progenitor cells into patients with hematologic disorders with the goal of re-establishing normal hematopoietic and immune function. HCT is classified as autologous or allogeneic based on the origin of hematopoietic cells. Autologous HCT uses the patient's own cells while allogeneic HCT uses hematopoietic cells from a human leukocyte antigen-compatible donor. Allogeneic HCT is a potentially curative treatment option for patients with certain types of hematologic malignancies, and autologous HCT is primarily used to support patients undergoing high-dose chemotherapy. Advances in HCT methods and supportive care in recent decades have led to improved survival after HCT; however, disease relapse and posttransplant complications still commonly occur in both autologous and allogeneic HCT recipients. Allogeneic HCT recipients may also develop acute and/or chronic graft-versus-host disease (GVHD), which results in immune-mediated cellular injury of several organs. The NCCN Guidelines for Hematopoietic Cell Transplantation focus on recommendations for pretransplant recipient evaluation and the management of GVHD in adult patients with malignant disease.

Treatment of acute myeloid leukemia in children: A practical perspective

Pediatric acute myeloid leukemia (AML) is a heterogeneous disease that requires a multifaceted treatment approach. Although outcomes for low-risk AML have improved significantly over recent decades, high-risk AML continues to be associated with an adverse prognosis. Recent advances in molecular diagnostics, risk stratification, and supportive care have contributed to improvements in outcomes in pediatric AML. Targeted approaches, for example, the use of tyrosine kinase inhibitors to treat FLT3-ITD AML, offer promise and are currently undergoing clinical investigation in pediatric patients. New approaches to hematopoietic stem cell transplantation, including the use of haploidentical donors, are significantly expanding donor options for patients with high-risk AML. This review provides an overview of recent advances in the treatment of pediatric AML that are likely to have clinical impact and reshape the standard of care.

Haploidentical Stem Cell Transplantation in Lymphomas-Expectations and Pitfalls

T-cell replete Haploidentical stem cell transplantation (Haplo-SCT) with Post-transplant cyclophosphamide (PT-Cy) is an emerging therapeutic option for patients with advanced relapsed or refractory lymphoma. The feasibility of this platform is supported by several retrospective studies showing a toxicity profile that is improved relative to umbilical cord blood and mismatched unrelated donor (UD) transplant and comparable to matched unrelated donor transplant. In particular, cumulative incidence of chronic graft-versus-host disease (GVHD) is reduced after Haplo-SCT relative to UD and matched related donor (MRD) transplant thanks to PT-Cy employed as GVHD prophylaxis. This achievement, together with a similar incidence of acute GVHD and disease relapse, results in a promising advantage of Haplo-SCT in terms of relapse-free/GVHD free survival. Unmet needs of the Haplo-SCT platform are represented by the persistence of a not negligible rate of non-relapse mortality, especially due to infections and disease relapse. Future efforts are warranted in order to reduce life-threatening infections and to employ Halo-SCT with PT-Cy as a platform to build new immunotherapeutic strategies.

Recent advances in allogeneic hematopoietic cell transplantation for acute myeloid leukemia

PURPOSE OF REVIEW

Allogeneic hematopoietic cell transplantation (HCT), with associated graft-versus-leukemia effects, remains the best postremission strategy for patients with intermediate or high-risk acute myeloid leukemia (AML), with a curative potential. Here, we highlight recent advances in allogeneic HCT that broadened access, refined prognostication, and improved outcomes of AML patients undergoing this procedure.

RECENT FINDINGS

Eligibility for allogeneic HCT continued to expand to AML patients older than 60 years, as well as to patients lacking human leukocyte antigen (HLA)-matched donors with the advent of alternative donor sources, such as umbilical cord blood and HLA-haploidentical transplantation. Molecular profiling of AML has redefined prognostication for patients in specific AML genomic subgroups undergoing allogeneic HCT and has served as a new strategy for measuring minimal residual disease before and after allogeneic HCT. Using high intensity conditioning regimens has emerged as a potential strategy to reduce risk of relapse and improve overall survival, especially in patients with minimal residual disease prior to allogeneic HCT.

SUMMARY

As access to allogeneic HCT continues to improve, also, with more refined prognostic strategies, the field continues to move to optimize transplantation approaches by decreasing the risk of relapse and minimizing transplant-related complications.

CTLA4Ig in an Extended Schedule along with Sirolimus Improves Outcome with a Distinct Pattern of Immune Reconstitution Following Post-Transplantation Cyclophosphamide-Based Haploidentical Transplantation for Hemoglobinopathies

The major hindrances to the success of a haploidentical hematopoietic cell transplantation for hemoglobinopathies are graft failure, early post-transplant hemophagocytic syndrome (PTHPS), and graft-versus-host disease (GVHD). Following the successful incorporation of CTLA4Ig (abatacept) in post-transplantation cyclophosphamide-based haploidentical transplantation, we piloted this approach in 10 patients (aged 3 to 19 years), with thalassemia major (TM, n=5) and sickle cell disease (n = 5). Pretransplant immunosuppressive therapy (pTIST) was administered for 10 weeks. Conditioning was myeloablative. CTLA4Ig was administered every 2 weeks during pTIST and on days -1, +5, +20, and +35 and every 4 weeks thereafter for 6 months, along with sirolimus. A short course of low-dose dexamethasone was given from day +6 for 14 days. Nine patients engrafted at a median of 15 days, with 1 patient with TM dying of sepsis on day +19. None of the patients developed acute or chronic GVHD. All 9 patients are alive and disease free at a median follow-up of 28 months. Only 4 patients had cytomegalovirus reactivation. The pattern of immune reconstitution showed a prompt and sustained recovery of T cell subsets with memory phenotype, along with early and sustained increase of Tregs and NKG2C⁺ natural killer (NK) cells. This novel approach, targeting CD80 and CD86 on monocytes/macrophages, promoted engraftment and limited early-onset PTHPS and graft failure. The lack of GVHD and serious infections with this approach reflects an early recovery of Tregs, memory T cells, and persistence of NKG2C⁺ NK cells.

Dissecting the biology of allogeneic HSCT to enhance the GvT effect whilst minimizing GvHD

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) was the first successful therapy for patients with haematological malignancies, predominantly owing to graft-versus-tumour (GvT) effects. Dramatic methodological changes, designed to expand eligibility for allo-HSCT to older patients and/or those with comorbidities, have led to the use of reduced-intensity conditioning regimens, in parallel with more aggressive immunosuppression to better control graft-versus-host disease (GvHD). Consequently, disease relapse has become the major cause of death following allo-HSCT. Hence, the prevention and treatment of relapse has come to the forefront and remains an unmet medical need. Despite >60 years of preclinical and clinical studies, the immunological requirements necessary to achieve GvT effects without promoting GvHD have not been fully established. Herein, we review learnings from preclinical modelling and clinical studies relating to the GvT effect, focusing on mechanisms of relapse and on immunomodulatory strategies that are being developed to overcome disease recurrence after both allo-HSCT and autologous HSCT. Emphasis is placed on discussing current knowledge and approaches predicated on the use of cell therapies, cytokines to augment immune responses and dual-purpose antibody therapies or other pharmacological agents that can control GvHD whilst simultaneously targeting cancer cells.