Nonmyeloablative Haploidentical Bone Marrow Transplantation with Post-Transplantation Cyclophosphamide for Pediatric and Young Adult Patients with High-Risk Hematologic Malignancies

Low-dose anti-thymocyte globulin plus low-dose posttransplant cyclophosphamide-based regimen for prevention of graft-versus-host disease in haploidentical peripheral blood stem cell transplantation for pediatric patients with hematologic malignancies

The low-dose anti-thymocyte globulin (ATG) plus low-dose post transplantation cyclophosphamide (PTCy) -based (low-dose ATG/PTCy-based) regimen had a promising activity in preventing of graft-versus-host disease (GVHD) in adult patients. However, its efficacy in pediatric patients remain to be defined. Here, we presented the findings from 35 pediatric patients undergoing haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) with the new regimen for GVHD prophylaxis. The cumulative incidences (CIs) of grades II-III and III-IV acute GVHD (aGVHD) were 34% (95% CI, 17-48%) and 11% (95% CI, 0-21%) within 180 days post-transplantation, respectively. The CIs of chronic GVHD (cGVHD) and moderate-to-severe cGVHD within 2 years were 26% (95% CI, 7-41%) and 12% (95% CI, 0-25%), respectively. The 2-year probabilities of overall survival, relapse-free survival, and graft-versus-host disease and relapse-free survival were 89% (95% CI, 78-100%), 82% (95% CI, 68-98%) and 59% (95% CI, 43-80%), respectively. The CIs of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) reactivation by day 180 were 37% (95% CI, 19-51%) and 20% (95% CI, 6-32%) respectively. These results strongly advocate for the efficacy of the low-dose ATG/PTCy-based regimen as a robust strategy for GVHD prevention in haplo-PBSCT for pediatric patients.

Improving Outcomes with Haploidentical Stem Cell Transplantation [HaploSCT] in Children Using Post-transplant Cyclophosphamide: a Single Center Experience

Haplo-identical stem cell transplant using post-transplant cyclophosphamide is increasingly being used in children without a matched sibling donor. Between 2010 and June 2021, 127 children underwent 138 transplants with a median age of 7.1 years for malignant and non-malignant disorders. Conditioning regimens included both myeloablative and reduced intensity regimens with peripheral blood stem cells as the main graft source. Engraftment occurred in 113 [81.9%] at a median of 16 days [range: 10-32] with primary graft failure in 10.2%. Cumulative incidence of grade II-IV acute graft versus host disease (GVHD) was 49.5% and chronic GVHD in 40.7%. Majority [92.7%] had at least one infection with 31% incidence of bacterial infection, 76% incidence of viral and 16% incidence of fungal infection. The 2-year overall survival (OS) is 54.9 ± 4.6% with a lower survival among young children aged 0-5 years [28.2 ± 6.4%] compared to 5-10 years [71.3 ± 6.8%] and 11-15 years [55.7 ± 8.8%] [p = 0.032]. 2-year OS has gradually improved from 25.0 ± 2.1% for 2010-2013 to 47.5 ± 6.2% for 2014-2017 and 67.1 ± 6.6% for 2018-2021 [p = 0.049]. On multivariate analysis, bacterial infection [p = 0.017], invasive fungal disease [p = 0.002] and graft failure [p = 0.029] negatively impacted overall survival. Haplo-identical SCT with post-transplant cyclophosphamide is a reasonable option for children who do not have a matched sibling donor. Strategies to reduce graft failure, infection related mortality and GVHD needs to be explored.

A Validated Risk Stratification That Incorporates MAGIC Biomarkers Predicts Long-Term Outcomes in Pediatric Patients with Acute GVHD

Acute graft versus host disease (GVHD) is a common and serious complication of allogeneic hematopoietic cell transplantation (HCT) in children but overall clinical grade at onset only modestly predicts response to treatment and survival outcomes. Two tools to assess risk at initiation of treatment were recently developed. The Minnesota risk system stratifies children for risk of nonrelapse mortality (NRM) according to the pattern of GVHD target organ severity. The Mount Sinai Acute GVHD International Consortium (MAGIC) algorithm of 2 serum biomarkers (ST2 and REG3α) predicts NRM in adult patients but has not been validated in a pediatric population. We aimed to develop and validate a system that stratifies children at the onset of GVHD for risk of 6-month NRM. We determined the MAGIC algorithm probabilities (MAPs) and Minnesota risk for a multicenter cohort of 315 pediatric patients who developed GVHD requiring treatment with systemic corticosteroids. MAPs created 3 risk groups with distinct outcomes at the start of treatment and were more accurate than Minnesota risk stratification for prediction of NRM (area under the receiver operating curve (AUC), .79 versus .62, P = .001). A novel model that combined Minnesota risk and biomarker scores created from a training cohort was more accurate than either biomarkers or clinical systems in a validation cohort (AUC .87) and stratified patients into 2 groups with highly different 6-month NRM (5% versus 38%, P < .001). In summary, we validated the MAP as a prognostic biomarker in pediatric patients with GVHD, and a novel risk stratification that combines Minnesota risk and biomarker risk performed best. Biomarker-based risk stratification can be used in clinical trials to develop more tailored approaches for children who require treatment for GVHD.

Disease Status and Interval between Hematopoietic Cell Transplantations Predict Outcome of Pediatric Patients Who Undergo Subsequent Transplantation for Relapsed Hematologic Malignancy

Patients with hematologic malignancies who relapse after allogeneic hematopoietic cell transplantation (HCT) have a poor prognosis. Although proceeding to subsequent HCT can provide potential for long-term survival, there are limited data to guide which patients are most likely to benefit and which HCT strategies are best in this heavily pretreated population. The goals of this study were to describe the clinical outcomes of subsequent HCT in pediatric patients with relapsed hematologic malignancies in a cohort enriched for haploidentical donors, and to evaluate the associations of patient-, disease-, and treatment-related factors with survival. We retrospectively evaluated patients who underwent a subsequent HCT for management of post-HCT relapse at a single institution between 2000 and 2021. Among 106 patients who underwent a second allogeneic HCT, the 1-year event-free survival (EFS) was 34% and 1-year overall survival (OS) was 46%, with a 5-year EFS of 26% and 5-year OS of 31%. Only disease-related factors were associated with outcome after second HCT-specifically, the interval between HCTs and the presence or absence of active disease at the time of HCT. In this cohort, patient- and treatment-related factors were not associated with differences in EFS or OS. Patients undergoing a third or fourth HCT (n = 13) had comparable survival outcomes to those undergoing a second HCT. Our experience highlights that a subsequent HCT has curative potential for a subset of patients who relapse after HCT, including those who undergo a subsequent HCT from a haploidentical donor. Although relapse and treatment-related toxicities remain major challenges, our study indicates that achieving complete remission prior to subsequent HCTs has the potential to further improve outcomes.

Incidence, Risk Factors, Characteristics, and Outcome of Chronic Graft Versus Host Disease in Children Undergoing Haploidentical Peripheral Blood Stem Cell Transplant With Post-transplant Cyclophosphamide

AIM

Chronic graft versus host disease (cGVHD) is a major cause of morbidity postallogeneic peripheral blood stem cell transplant (PBSCT). There is paucity of literature describing incidence, risk factors, characteristics, and outcome of cGVHD in children undergoing haploidentical PBSCT with post-transplant cyclophosphamide (PTCy). Here, we describe our experience from our center regarding the same.

METHODS

All children who underwent haploidentical PBSCT with PTCy between January 2016 and December 2021 at our center and survived beyond day+100 post-transplant were included in this retrospective study. Conditioning regimens used were: Thiotepa-Fludarabine-Cyclophosphamide with 2 Gy single fraction total body irradiation, Thiotepa-Busulfan-Fludarabine, Fludarabine-total body irradiation and Fludarabine-Melphalan. Peripheral blood was used as stem cell source in all patients. GVHD prophylaxis was PTCy 50 mg/kg on day +3 and +4, Mycophenolate mofetil and Calcineurin inhibitors. Clinical and laboratory data was electronically retrieved and analyzed based on National Institute of Health Consensus Criteria-2014 at regular intervals. Impact of various patient, donor, and transplant-related factors on development of cGVHD were analyzed. Incidence of relapse, event free survival (EFS) and overall survival (OS) were calculated and compared between cGVHD and no cGVHD groups. Patients with rejection were excluded from risk factor analysis for cGVHD but were considered for survival analysis.

RESULTS

Fifty-one children included in this study. Median age of transplant of our cohort was 7.5 years with male:female=1.6:1. Eight patients had rejection with autologous recovery. History of acute GVHD (aGVHD) was present in 15/51 (Grade III to IV in 7/51). cGVHD developed in 19/51 patients (mild-9/51, moderate-6/51, and severe-4/51). Skin was the most common organ involved (100%) followed by gastrointestinal tract (47.4%), liver (36.8%), eyes (21%), lungs (21%), mouth (15.7%), and joints (5.2%). Advanced donor age (>30 y) and previous aGVHD were found to be significantly associated with increased risk of developing cGVHD. At last follow-up, complete response and partial response of cGVHD was seen in 6/19 and 4/19 patients, respectively. Overall mortality was 15/51 (cause of mortality was relapse of cancer 8/15, cGVHD-3/15, other 4/15). EFS and OS of full cohort was 55% and 70.6%, respectively. Compared with patients without cGVHD, patients with cGVHD demonstrated a lower relapse (18.2% vs. 40%, P =0.2333), higher EFS (68.4% vs. 53.1%, P =0.283), and higher OS (73.7% vs. 68.8%, P =0.708).

CONCLUSION

Incidence of cGVHD was high in children undergoing haploidentical PBSCT with PTCy. Other than PBSC graft source; donor age and previous aGVHD were the risks factors for development of cGVHD. Patients with cGVHD had lower incidence of relapse translating into better survival but this difference was not statistically significant.

Prospective PTCTC trial of myeloablative haplo-BMT with posttransplant cyclophosphamide for pediatric acute leukemias

Promising results have been reported for adult patients with high-risk hematologic malignancies undergoing haploidentical bone marrow transplant (haploBMT) with posttransplant cyclophosphamide (PTCy). To our knowledge, we report results from the first multicenter trial for pediatric and young adult patients with high-risk acute leukemias and myelodysplastic syndrome (MDS) in the Pediatric Transplantation and Cellular Therapy Consortium. Nine centers performed transplants in 32 patients having acute leukemias or MDS, with myeloablative conditioning (MAC), haploBMT with PTCy, mycophenolate mofetil, and tacrolimus. The median patient age was 12 years. Diagnoses included AML (15), ALL (11), mixed-lineage leukemia (1), and MDS (5). Transplant-related mortality (TRM) at 180 days was 0%. The cumulative incidence (CuI) of grade 2 acute graft-versus-host disease (aGVHD) on day 100 was 13%. No patients developed grades 3-4 aGVHD. The CuI of moderate-to-severe chronic GVHD (cGVHD) at 1 year was 4%. Donor engraftment occurred in 27 patients (84%). Primary graft failures included 3 patients who received suboptimal bone marrow grafts; all successfully engrafted after second transplants. The CuI of relapse at 1 year was 32%, with more relapse among patients MRD positive pre-BMT vs MRD negative. Overall survival rates at 1 and 2 years were 77% and 73%, and event-free survival rate at 1 and 2 years were 68% and 64%. There was no TRM or severe aGVHD, low cGVHD, and favorable relapse and survival rates. This successful pilot trial has led to a phase 3 trial comparing MAC haploBMT vs HLA-matched unrelated donor BMT in the Children's Oncology Group. This trial was registered at www.clinicaltrials.gov as #NCT02120157.

Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis

BACKGROUND

In patients undergoing allogeneic hematopoietic stem-cell transplantation (HSCT), a calcineurin inhibitor plus methotrexate has been a standard prophylaxis against graft-versus-host disease (GVHD). A phase 2 study indicated the potential superiority of a post-transplantation regimen of cyclophosphamide, tacrolimus, and mycophenolate mofetil.

METHODS

In a phase 3 trial, we randomly assigned adults with hematologic cancers in a 1:1 ratio to receive cyclophosphamide-tacrolimus-mycophenolate mofetil (experimental prophylaxis) or tacrolimus-methotrexate (standard prophylaxis). The patients underwent HSCT from an HLA-matched related donor or a matched or 7/8 mismatched (i.e., mismatched at only one of the HLA-A, HLA-B, HLA-C, and HLA-DRB1 loci) unrelated donor, after reduced-intensity conditioning. The primary end point was GVHD-free, relapse-free survival at 1 year, assessed in a time-to-event analysis, with events defined as grade III or IV acute GVHD, chronic GVHD warranting systemic immunosuppression, disease relapse or progression, and death from any cause.

RESULTS

In a multivariate Cox regression analysis, GVHD-free, relapse-free survival was significantly more common among the 214 patients in the experimental-prophylaxis group than among the 217 patients in the standard-prophylaxis group (hazard ratio for grade III or IV acute GVHD, chronic GVHD, disease relapse or progression, or death, 0.64; 95% confidence interval [CI], 0.49 to 0.83; P = 0.001). At 1 year, the adjusted GVHD-free, relapse-free survival was 52.7% (95% CI, 45.8 to 59.2) with experimental prophylaxis and 34.9% (95% CI, 28.6 to 41.3) with standard prophylaxis. Patients in the experimental-prophylaxis group appeared to have less severe acute or chronic GVHD and a higher incidence of immunosuppression-free survival at 1 year. Overall and disease-free survival, relapse, transplantation-related death, and engraftment did not differ substantially between the groups.

CONCLUSIONS

Among patients undergoing allogeneic HLA-matched HSCT with reduced-intensity conditioning, GVHD-free, relapse-free survival at 1 year was significantly more common among those who received cyclophosphamide-tacrolimus-mycophenolate mofetil than among those who received tacrolimus-methotrexate. (Funded by the National Heart, Lung, and Blood Institute and others; BMT CTN 1703 ClinicalTrials.gov number, NCT03959241.).

Total body irradiation-free haploidentical peripheral blood stem cell transplantation compared to related and unrelated donor transplantation in pediatrics with acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most prevalent childhood cancer under the age of 15 years. Despite the recent advances in therapeutic regimens, relapse occurs in 15%-20% of pediatric patients after chemotherapy, and hematopoietic stem cell transplantation (HSCT) is the best treatment option. However, donor availability is one of the major challenges. Over the last decade, haploidentical donor (HID) transplantation has evolved as an alternative option. Herein, we aimed to compare the transplant outcomes in pediatric patients receiving total body irradiation (TBI)-free myeloablative regimens, between non-HID and HID transplant.

PATIENTS AND METHODS

The study included 60 pediatric ALL patients who had undergone HSCT from October 2016 until September 2020. Forty-three patients received non-HID HSCT, while 17 patients received HID. The sources of stem cells (SC) were peripheral blood stem cells (PBSC) for all the patients. The conditioning regimen was based on busulfan and cyclophosphamide. For graft-versus-host disease (GvHD) prophylaxis, patients received cyclosporine and methotrexate in the setting of non-HID transplantation, where HIDs received post-transplant cyclosporine and cyclophosphamide.

RESULTS

The cumulative incidences of 3-year overall survival (OS) were 73.1%, 66.6%, and 69.5%, for matched sibling donor-matched related donor (MSD-MRD), matched unrelated donor-mismatched unrelated donor (MUD-MMUD), and HID groups, respectively (p = .85). The cumulative incidences of grade II-IV acute GvHD for the MRD, MUD-MMUD, and HID groups were 29%, 41%, and 49%, respectively (p = .47). Furthermore, the 3-year cumulative incidence of chronic GvHD was MSD-MRD: 70% versus MUD-MMUD: 42% versus HID: 45% (p = .64). The 3-year cumulative incidence of relapse post transplantation was 45%, 18%, and 45%, respectively, for the MSD-MRD, MUD-MMUD, and HID groups, and the differences were not statistically significant (p = .55). There was a higher risk for cytomegalovirus (CMV) infection in patients receiving HID transplants compared to those of non-HIDs (p < .01).

CONCLUSION

Our results indicate that PBSC-HID transplant outcomes in the setting of non-TBI conditioning are comparable to those of non-HIDs in pediatric ALL patients.

Effective T-cell replete haploidentical stem cell transplantation for pediatric patients with high-risk hematologic disorders

OBJECTIVES

Patients with high-risk hematologic diseases require intensive modalities, including high-dose chemotherapy and allogeneic hematopoietic stem cell transplantation (allo-HSCT). Haploidentical T-cell-replete transplantation is a logical choice because of the limited availability of matched sibling donors and the prolonged time needed to identify matched unrelated donors in Thailand.

METHODS

The clinical outcomes data of 43 patients undergoing allo-HSCT were reviewed. All patients had high-risk hematologic malignancies, were younger than 20 years, and were in complete cytological remission at the time of allo-HSCT. We used two different conditioning regimens: total body irradiation (TBI) combined with cyclophosphamide, fludarabine, and melphalan (n = 23) and thiotepa combined with fludarabine and busulfan (n = 20). All patients received a graft-versus-host disease prophylaxis regimen consisting of cyclophosphamide, mycophenolate mofetil, and a calcineurin inhibitor or sirolimus.

RESULTS

There was no difference in engraftment between patients receiving either of the regimens. After a median follow-up of 35.8 (range, 0.6-106.2) months, the overall survival (OS) and event-free survival (EFS) rates were 62.4% and 54.7%, respectively. OS and EFS were comparable between the respective regimens.

CONCLUSIONS

We conclude that thiotepa-based conditioning has similar efficacy and tolerability as TBI-based conditioning for haploidentical HSCT with post-transplant cyclophosphamide.

HLA-haploidentical hematopoietic stem cells transplantation with regulatory and conventional T-cell adoptive immunotherapy in pediatric patients with very high-risk acute leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) is still needed for many children with very high-risk acute leukemia. An HLA-haploidentical family donor is a suitable option for those without an HLA-matched donor. Here we present outcomes of a novel HLA-haploidentical HSCT (haplo-HSCT) strategy with adoptive immunotherapy with thymic-derived CD4⁺CD25⁺ FoxP3⁺ regulatory T cells (Tregs) and conventional T cells (Tcons) performed between January 2017 and July 2021 in 20 children with high-risk leukemia. Median age was 14.5 years (range, 4-21), 15 had acute lymphoblastic leukemia, 5 acute myeloid leukemia. The conditioning regimen included total body irradiation (TBI), thiotepa, fludarabine, cyclophosphamide. Grafts contained a megadose of CD34+ cells (mean 12.4 × 10⁶/Kg), Tregs (2 × 10⁶/Kg) and Tcons (0.5-1 × 10⁶/Kg). All patients achieved primary, sustained full-donor engraftment. Only one patient relapsed (5%). The incidence of non-relapse mortality was 15% (3/20 patients). Five/20 patients developed ≥ grade 2 acute Graft versus Host Disease (aGvHD). It resolved in 4 who are alive and disease-free; 1 patient developed chronic GvHD (cGvHD). The probability of GRFS was 60 ± 0.5% (95% CI: 2.1-4.2) (Fig. 6), CRFS was 79 ± 0.9% (95% CI: 3.2-4.9) as 16/20 patients are alive and leukemia-free. The median follow-up was 2.1 years (range 0.5 months-5.1 years). This innovative approach was associated with very promising outcomes of HSCT strategy in pediatric patients.

Antithymocyte Globulin Plus Post-Transplant Cyclophosphamide Combination as an Effective Strategy for Graft-versus-Host Disease Prevention in Haploidentical Peripheral Blood Stem Cell Transplantation for Children with High-Risk Malignancies

Haploidentical hematopoietic stem cell transplantation using post-transplant cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis has emerged as a valid alternative transplant strategy for patients lacking a suitable HLA-matched related donor. The high risk of severe GVHD remains the major clinical challenge in this setting. The addition of antithymocyte globulin (ATG) in PTCy-based regimens for GVHD reduction in haploidentical hematopoietic stem cell transplantation is rational and was reported in adult series. However, its feasibility is unknown in pediatric patients. Here, we firstly describe our experience of 15 consecutive children with high-risk malignancies receiving haploidentical peripheral blood stem cell transplantation using ATG plus PTCy for GVHD prophylaxis. Only three patients developed grade 1-2 acute GVHD, limited to skin. No grade 3-4 acute GVHD and chronic GVHD were observed. Viral reactivations were frequently seen but manageable. Six patients relapsed, as the main cause of death in our series. None died from events related to GVHD. Our data suggest that ATG plus PTCy is an effective strategy for GVHD prevention in haploidentical peripheral blood stem cell transplantation and is feasible in children with high-risk malignancies.

IL-33 acts as a costimulatory signal to generate alloreactive Th1 cells in graft-versus-host disease

Antigen-presenting cells (APCs) integrate signals emanating from local pathology and program appropriate T cell responses. In allogeneic hematopoietic stem cell transplantation (alloHCT), recipient conditioning releases damage-associated molecular patterns (DAMPs) that generate proinflammatory APCs that secrete IL-12, which is a driver of donor Th1 responses, causing graft-versus-host disease (GVHD). Nevertheless, other mechanisms exist to initiate alloreactive T cell responses, as recipients with disrupted DAMP signaling or lacking IL-12 develop GVHD. We established that tissue damage signals are perceived directly by donor CD4+ T cells and promoted T cell expansion and differentiation. Specifically, the fibroblastic reticular cell-derived DAMP IL-33 is increased by recipient conditioning and is critical for the initial activation, proliferation, and differentiation of alloreactive Th1 cells. IL-33 stimulation of CD4+ T cells was not required for lymphopenia-induced expansion, however. IL-33 promoted IL-12-independent expression of Tbet and generation of Th1 cells that infiltrated GVHD target tissues. Mechanistically, IL-33 augmented CD4+ T cell TCR-associated signaling pathways in response to alloantigen. This enhanced T cell expansion and Th1 polarization, but inhibited the expression of regulatory molecules such as IL-10 and Foxp3. These data establish an unappreciated role for IL-33 as a costimulatory signal for donor Th1 generation after alloHCT.

What Is the Role of HSCT in Philadelphia-Chromosome-Positive and Philadelphia-Chromosome-Like ALL in the Tyrosine Kinase Inhibitor Era?

Previously, the outcome of paediatric Philadelphia-chromosome-positive (Ph+) ALL treated with conventional chemotherapy alone was poor, necessitating the use of haematopoietic stem cell transplantation (HSCT) for the best outcomes. The recent addition of tyrosine kinase inhibitors (TKIs) alongside the chemotherapy regimens for Ph+ ALL has markedly improved outcomes, replacing the need for HSCT for lower risk patients. An additional poor prognosis group of Philadelphia-chromosome-like (Ph-like) ALL has also been identified. This group also can be targeted by TKIs in combination with chemotherapy, but the role of HSCT in this population is not clear. The impact of novel targeted immunotherapies (chimeric antigen receptor T cells and bispecific or drug-conjugated antibodies) has improved the outcome of patients, in combination with chemotherapy, and made the role of HSCT as the optimal curative therapy for Ph+ ALL and Ph-like ALL less clear. The prognosis of patients with Ph+ ALL and persistent minimal residual disease (MRD) at the end of consolidation despite TKI therapy or with additional genetic risk factors remains inferior when HSCT is not used. For such high-risk patients, HSCT using total-body-irradiation-containing conditioning is currently recommended. This review aims to provide an update on the current and future role of HSCT for Ph+ ALL and addresses key questions related to the management of these patients, including the role of HSCT in first complete remission, MRD evaluation and related actions post HSCT, TKI usage post HSCT, and the putative role of HSCT in Ph-like ALL.

Chimeric Antigen Receptor T-Cell Therapy in Paediatric B-Cell Precursor Acute Lymphoblastic Leukaemia: Curative Treatment Option or Bridge to Transplant?

Chimeric antigen receptor T-cell therapy (CAR-T) targeting CD19 has been associated with remarkable responses in paediatric patients and adolescents and young adults (AYA) with relapsed/refractory (R/R) B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). Tisagenlecleucel, the first approved CD19 CAR-T, has become a viable treatment option for paediatric patients and AYAs with BCP-ALL relapsing repeatedly or after haematopoietic stem cell transplantation (HSCT). Based on the chimeric antigen receptor molecular design and the presence of a 4-1BB costimulatory domain, tisagenlecleucel can persist for a long time and thereby provide sustained leukaemia control. "Real-world" experience with tisagenlecleucel confirms the safety and efficacy profile observed in the pivotal registration trial. Recent guidelines for the recognition, management and prevention of the two most common adverse events related to CAR-T - cytokine release syndrome and immune-cell-associated neurotoxicity syndrome - have helped to further decrease treatment toxicity. Consequently, the questions of how and for whom CD19 CAR-T could substitute HSCT in BCP-ALL are inevitable. Currently, 40-50% of R/R BCP-ALL patients relapse post CD19 CAR-T with either CD19- or CD19+ disease, and consolidative HSCT has been proposed to avoid disease recurrence. Contrarily, CD19 CAR-T is currently being investigated in the upfront treatment of high-risk BCP-ALL with an aim to avoid allogeneic HSCT and associated treatment-related morbidity, mortality and late effects. To improve survival and decrease long-term side effects in children with BCP-ALL, it is important to define parameters predicting the success or failure of CAR-T, allowing the careful selection of candidates in need of HSCT consolidation. In this review, we describe the current clinical evidence on CAR-T in BCP-ALL and discuss factors associated with response to or failure of this therapy: product specifications, patient- and disease-related factors and the impact of additional therapies given before (e.g., blinatumomab and inotuzumab ozogamicin) or after infusion (e.g., CAR-T re-infusion and/or checkpoint inhibition). We discuss where to position CAR-T in the treatment of BCP-ALL and present considerations for the design of supportive trials for the different phases of disease. Finally, we elaborate on clinical settings in which CAR-T might indeed replace HSCT.

Incidence and Outcomes of Respiratory Failure After Non-Myeloablative Related Haploidentical Blood or Marrow Transplant

BACKGROUND

Respiratory failure is a devastating complication of allogenic blood or marrow transplant (BMT). Prior data suggest 20% and 15% of BMT patients develop respiratory failure and ARDS, respectively. Non-myeloablative (NMA) haploidentical BMT allows donor pool expansion and may decrease complications. Incidence, outcomes, and risk factors for respiratory failure after NMA haploidentical BMT are unknown.

RESEARCH QUESTION

Determine the incidence of respiratory failure after NMA haploidentical BMT and explore outcomes and risk factors for respiratory failure.

STUDY DESIGN AND METHODS

Single-center, retrospective study of all patients > 18 years old undergoing NMA haploidentical BMT from 2004-2016. The primary outcome was respiratory failure (high-flow nasal cannula oxygen, non-invasive ventilation [NIV], or invasive mechanical ventilation [IMV]) within 2 years after BMT. Respiratory failure incidence is reported as incidence rate ratios (IRR) with 95% confidence intervals. Unadjusted and multivariable Cox proportional hazards models with adjustment for a priori identified patient-level characteristics were used. Results are presented as hazard ratios (HR) with 95% CIs.

RESULTS

520 patients underwent NMA haploidentical BMT; 82 (15.8%) developed respiratory failure (IRR 0.114/person-year) at a median of 0.34 years (25^th, 75^th percentiles 0.06, 0.75 years) after BMT. Older age (HR 1.04, 1.02, 1.07), transplant for MDS (HR 1.99, 1.07, 3.72), and parent donor (HR 3.49, 1.32, 9.26) were associated with increased risk of respiratory failure; higher pre-transplant DLCO (% pred) was associated with lower risk (HR 0.98, 0.77, 0.99). Sixty-one (11.7%) patients required IMV; 30 were successfully extubated. Only 37 (7%) patients had ARDS. Of the 82 with respiratory failure, 43 (52.4%) and 61 (77.2%) died during index hospitalization and by 2 years, respectively. Only 40 (49%) had non-relapse mortality.

INTERPRETATION

Incidence of respiratory failure and ARDS after NMA haploidentical BMT is modest at 15% by 2 years after transplant. Despite successful extubation in more than 50% of patients, respiratory failure, regardless of cause, is associated with a high rate of death by 2 years, from both relapse and non-relapse causes. Age, BMT for MDS, parental donor, and pre-transplant DLCO were risk factors for respiratory failure.

Effects of second transplantation with T-cell-replete haploidentical graft using low-dose anti-thymocyte globulin on long-term overall survival in pediatric patients with relapse of leukemia after first allogeneic transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the preferred treatment for children with high-risk hematologic malignancies, but post-allo-HSCT relapse has a poor prognosis and limited treatment options. We evaluated the feasibility, outcome, and risk factors influencing survival after T-cell-replete haploidentical HSCT with low-dose anti-thymocyte globulin (ATG) in 30 patients with post-allo-HSCT relapse of acute lymphoblastic leukemia and acute myeloid leukemia. Overall, 50% of the patients had complete remission (CR) before the second transplant and the overall survival (OS) rate was 52%. In surviving patients (median follow-up 614 days), Kaplan-Meier analysis revealed estimated 2-year leukemia-free survival and OS rates of 48.1% and 61.1%, respectively. Cumulative incidences of 2-year non-relapse mortality and relapse were 24.7% and 36.3%, respectively. Achieving CR before the second allo-HSCT was a predominant independent prognostic factor identified in the multivariate analysis, with a significantly improved 2-year OS rate of 86.7%. T-cell-replete haplo-HSCT with low-dose ATG for second allo-HSCT may benefit a selected patient population.

Outcome of Haploidentical Peripheral Blood Allografts Using Post-Transplantation Cyclophosphamide Compared to Matched Sibling and Unrelated Donor Bone Marrow Allografts in Pediatric Patients with Hematologic Malignancies: A Single-Center Analysis

The introduction of post-transplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis has made haploidentical (haplo) hematopoietic stem cell transplantation (HSCT) a common approach in adults, but pediatric experience is limited. Based on the encouraging adult data and with the aim of decreasing the risk of graft failure, our center is increasingly using peripheral blood stem cells (PBSCs) from haplo donors with PTCy. Here we compare outcomes of bone marrow (BM) transplantation with traditional donor choices, including matched sibling donors (MSDs) and 10/10 HLA matched unrelated donors (MUDs), with those of haplo PBSC grafts in pediatric patients with hematologic malignancies. In this retrospective single-center study, the primary endpoint was the comparison of GVHD-free relapse-free survival (GRFS; defined as absence of acute GVHD [aGVHD] grade III-IV, relapse, death, or chronic GVHD [cGVHD] requiring systemic therapy) for the 3 cohorts. Secondary endpoints included overall survival (OS), relapse-free survival (RFS), nonrelapse mortality (NRM), and incidence of aGVHD and cGVHD). A total of 104 consecutive patients underwent first allogeneic (allo)-HSCT for a hematologic malignancy or myelodysplastic syndrome between January 2014 and December 2020 using a haplo family donor (PBSCs; n = 26), an MSD (BM; n = 31), or an MUD (BM; n = 47). Patient demographic and transplantation characteristics were not significantly different across the cohorts, apart from remission status, with the haplo cohort having more patients in third or later complete remission before HSCT (P < .01). The median duration of follow-up for the entire cohort was 573 days. The cumulative incidence of aGVHD (grade II-IV or grade III-IV) was not significantly different among the cohorts; however, the cumulative incidence of cGVHD at 18 months was highest in the MUD cohort (31.7%, versus 10.0% in the MSD cohort and 9.2% in the haplo cohort; P = .02). There were no differences in the 18-month cumulative incidence of relapse or NRM. OS and RFS at 18 months were 80.7% (95% confidence interval [CI], 61.7% to 100%) and 73.8% (95% CI, 55.5% to 98.1%) for the haplo cohort, 83.4% (95% CI, 72.8% to 95.5%) and 70.3% (95% CI, 57.9% to 85.3%) for the MUD cohort, and 80.9% (95% CI, 66.9% to 97.7%) and 66.5% (95% CI, 50.5% to 87.5%) for the MSD cohort, with no statistically significant differences among the cohorts. GRFS at 18 months was 61% (95% CI, 43.3% to 85.9%) for the haplo cohort, 44.6% (95% CI, 31.8% to 62.5%) for the MUD cohort, and 62.1% (95% CI, 45.7% to 84.3%) for the MSD cohort (P = .26). Haploidentical PBSC HSCT with PTCy had comparable outcomes to MSD and MUD BM HSCT and less cGVHD compared with MUD BM HSCT in children. The logistical advantages and lower resource burden of haplo HSCT with PBSCs make it a feasible alternative to MUD HSCT in children with hematologic malignancies. Nonetheless, given that this is a retrospective comparison of transplantation platforms rather than donor types, further prospective studies are warranted. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Case Report: Haploidentical Bone Marrow Transplantation in Two Brothers With Wiskott-Aldrich Syndrome Using Their Father as the Donor

Wiskott-Aldrich syndrome (WAS) is an X-linked genetic disorder with a variable phenotypic expression that includes thrombocytopenia, eczema, and immunodeficiency. Some patients may also exhibit autoimmune manifestations. Patients with WAS are at increased risk of developing malignancies such as lymphoma. Allogeneic hematopoietic cell transplantation remains the only curative treatment. Haploidentical bone marrow transplantation (haplo-BMT) with post-transplant cyclophosphamide (PT-CY) has more recently been applied in WAS. Here, we report two brothers who underwent successful T-cell replete haplo-BMT with PT-CY at ages 9 months and 4 years using their father as the donor. Our myeloablative regimen was well-tolerated with minimal organ toxicity and no acute or chronic graft vs. host disease (GvHD). Haplo-BMT may be considered as a safe and effective option for patients with WAS who do not have available human leukocyte antigen (HLA) matched donors.

Impact of mother donor, peripheral blood stem cells and measurable residual disease on outcomes after haploidentical hematopoietic cell transplantation with post-transplant cyclophosphamide in children with acute leukaemia

Haploidentical hematopoietic-cell transplantation using post-transplant cyclophosphamide(Haplo-PTCy) is a feasible procedure in children with haematologic malignancies. However, data of a large series of children with acute leukaemia(AL) in this setting is missing. We analysed 144 AL Haplo-PTCy paediatric recipients; median age was 10 years. Patients had acute lymphoblastic(ALL; n = 86) or myeloblastic leukaemia(AML; n = 58) and were transplanted in remission(CR1: n = 40; CR2: n = 57; CR3+: n = 27) or relapse (n = 20). Bone marrow was the graft source in 57%; donors were father (54%), mother (35%), or sibling (11%). Myeloablative conditioning was used in 87%. Median follow-up was 31 months. At day +100, cumulative incidence (CI) of neutrophil recovery and acute GVHD (II-IV) were 94% and 40%, respectively. At 2-years, CI of chronic GVHD and relapse, were 31%, 40%, and estimated 2-year overall survival (OS), leukaemia-free survival (LFS) and graft-versus-host-relapse-free survival (GRFS) were 52%, 44% and 34% respectively. For patients transplanted in remission, positive measurable residual disease (MRD) prior to transplant was associated with decreased LFS (p = 0.05) and GRFS (p = 0.003) and increased risk of relapse (p = 0.02). Mother donor was associated with increased risk of chronic GVHD (p = 0.001), decreased OS (p = 0.03) and GRFS (p = 0.004). Use of PBSC was associated with increased risk of chronic GVHD (p = 0.04). In conclusion, achieving MRD negativity pre-transplant, avoiding use of mother donors and PBSC as graft source may improve outcomes of Haplo-PTCy in children with AL.

Improved transplant outcomes with myeloablative conditioning for hemophagocytic lymphohistiocytosis in HLA-matched and mismatched donors: a national multicenter retrospective study

We report the results of national retrospective study of 45 children with hemophagocytic lymphohistiocytosis (HLH) who underwent allogeneic hematopoietic stem-cell transplantation (HSCT) in Israel between the years 2000-2018. Donors were either HLA-matched (n = 26), partially mismatched (n = 7), haploidentical (n = 8), or cord-blood (n = 4). Myeloablative conditioning (MAC) was used in 20 procedures, and reduced-intensity conditioning (RIC) in 25. Forty-two patients engrafted, two had primary graft failure (one successfully retransplanted), one died prior to engraftment, and two developed secondary graft failure. Of the eight patients who had mixed donor chimerism at day 30 (5-95%), five achieved stable mixed or full donor chimerism. The 5-year probabilities of overall survival and event-free survival (EFS) were 86% and 82%, respectively. Five-year EFS was lower for patients receiving RIC compared to MAC (72% vs. 100%, p = 0.018) and following alternative-donor transplant (68% vs. 92% for HLA-matched donors, p = 0.034), mostly due to increased transplant-related mortality (TRM). Thus, both HLA-matched and alternative donor transplant procedures may benefit form a myeloablative conditioning regimen.

Salvage HLA-haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide for graft failure in non-malignant disorders

Graft failure requires urgent salvage HSCT, but there is no universally accepted approach for this situation. We investigated T-cell replete haploidentical HSCT with post-transplantation cyclophosphamide following serotherapy-based, radiation-free, reduced intensity conditioning in children with non-malignant disorders who had rejected their primary graft. Twelve patients with primary or secondary graft failure received T-cell replete bone marrow grafts from haploidentical donors and post-transplantation cyclophosphamide. The recommended conditioning regimen comprised rituximab 375 mg/m2, alemtuzumab 0.4 mg/kg, fludarabine 150 mg/m2, treosulfan 20-24 g/m2 and cyclophosphamide 29 mg/kg. After a median follow-up of 26 months (7-95), eleven of twelve patients (92%) are alive and well with complete donor chimerism in ten. Neutrophil and platelet engraftment were observed in all patients after a median of 18 days (15-61) and 39 days (15-191), respectively. Acute GVHD grade I was observed in 1/12 patients (8%) and mild chronic GVHD in 1/12 patients (8%). Viral reactivations and disease were frequent complications at 75% and 42%, respectively, but no death from infectious causes occurred. In summary, this retrospective analysis demonstrates that a post-transplantation cyclophosphamide-based HLA-haploidentical salvage HSCT after irradiation-free conditioning results in excellent engraftment and overall survival in children with non-malignant diseases.

Successful mismatched hematopoietic stem cell transplantation for pediatric hemoglobinopathy by using ATG and post-transplant cyclophosphamide

The use of HLA-mismatched (un)related donors is historically associated with a higher incidence of transplant-related complications and mortality. However, the use of such donors may overcome the limited availability of HLA-matched donors for patients with β-thalassemia major (TM) and sickle cell disease (SCD). We investigated hematopoietic stem cell transplantation (HSCT) outcomes of pediatric TM and SCD patients treated with a mismatched donor using a treosulfan-based conditioning in combination with ATG and post-transplant cyclophosphamide (PT-CY) and compared these results to the clinical outcome of patients treated by matched donor HSCT without PT-CY. Thirty-eight children (n = 24 HLA-identical or 10/10-matched donors; n = 14 HLA-mismatched donors), who received a non-depleted bone marrow graft were included. Event-free survival (EFS) and GvHD were not higher in the mismatched PT-Cy group as compared to the matched group. Moreover, despite delayed neutrophil engraftment (day +22 vs. +26, p = 0.002) and immune recovery in the mismatched PT-Cy group, this did not result in more infectious complications. Therefore, we conclude that in the absence of an HLA-identical or a matched unrelated donor, HSCT with a mismatched unrelated or haploidentical donor in combination with ATG plus PT-CY can be considered a safe and effective treatment option for pediatric hemoglobinopathy patients.

Myeloablative haploidentical BMT with posttransplant cyclophosphamide for hematologic malignancies in children and adults

Promising results have been reported for patients with high-risk hematologic malignancies undergoing HLA-haploidentical bone marrow transplantation (haploBMT) with posttransplantation cyclophosphamide (PTCy), but there are few data on outcomes with myeloablative conditioning in this context. We report the results of a single-institution, prospective phase 2 trial of myeloablative haploBMT using busulfan-based or total body irradiation-based conditioning in 96 children or adults (median age, 42 years; range, 1-65 years) with high-risk hematologic malignancies. Recovery of neutrophils and platelets occurred at a median of 24 and 29 days. Engraftment of donor cells with chimerism >95% was achieved in 91%. The cumulative incidence of acute graft-versus-host disease (GVHD) grades II to IV and grades III to IV at day 100 was 11% and 4%, and of chronic GVHD at 6 and 12 months was 4% and 15%, with 6% moderate to severe. The cumulative incidence of nonrelapse mortality was 6% at 100 days and 11% at 1 year (19% in those aged >55 years). The cumulative incidence of relapse at 1 year was 35%; at 3 years, it was 43%. In multivariable analysis, relapse was associated with increased age (P = .02 for age 20-55 years and P = .02 for age >55 years) and with minimal residual disease before transplantation (P = .05). The overall survival at 1 and 3 years is 73% and 54%, and event-free survival at 1 and 3 years is 57% and 49%. We show that haploBMT with PTCy after myeloablative conditioning is safe and efficacious for adult and pediatric patients with hematologic malignancies. Careful consideration must be given to using myeloablative conditioning in patients age >55 years. This trial was registered at www.clinicaltrials.gov as #NCT00796562.

Contemporary haploidentical stem cell transplant strategies in children with hematological malignancies

The barriers to HLA-mismatched or haploidentical hematopoietic stem cell transplantation (HSCT), namely GvHD and graft failure, have been overcome with novel transplant platforms. Post-transplant Cyclophosphamide (PTCy) is widely available, feasible and easy to implement. TCRαβ T and B cell depletion comes with consistent GvHD preventive benefits irrespective of age and indication. Naive T-cell depletion helps prevention of severe viral reactivations. The Beijing protocol shows promising outcomes in patients with poor remission status at the time of transplantation. For children, the toxicities and late outcomes related to these transplants are truly relevant as they suffer the most in the long run from transplant-related toxicities, especially chronic GvHD. While comparing the outcomes of different Haplo-HSCT approaches, one must understand the transplant immunobiology and factors affecting the transplant outcomes. Leukemia remission status at the time of conditioning is a consistent factor affecting the transplant outcomes using any of these platforms. Prospective comparison of these platforms lacks in a homogenous population; however, the evidence is growing, and this review highlights the areas of research gaps.

Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide in Children with High-Risk Leukemia Using a Reduced-Intensity Conditioning Regimen and Peripheral Blood as the Stem Cell Source

The use of haploidentical donor hematopoietic stem cell transplantation with post-transplantation cyclophosphamide (Haplo-PTCy) in children is increasing; however, it is still not clear which preparative regimen is best in this setting. We present the long-term results of 42 patients age <18 years with high-risk leukemia who underwent this procedure using a reduced-intensity conditioning regimen (RIC) and peripheral blood as the stem cell source. Twenty-six patients had acute lymphoblastic leukemia, 13 had acute myelogenous leukemia, 2 had juvenile myelomonocytic leukemia, and 1 had blast crisis of chronic myelogenous leukemia. One-third of the patients were in first remission, 50% were in second remission, 14% were in third remission, and 3% had refractory disease. Neutrophil recovery occurred in 100% of the 40 patients alive at day +30, and transplantation-related mortality at 1 year was 14%. The incidence of acute graft-versus-disease (GVHD) grade III-IV was 17%, and the cumulative incidence of moderate to severe chronic GVHD at 1 year was 29%. The median duration of follow-up for surviving patients was 45 months; overall survival and event-free survival at 36 months were 56% and 46%, respectively. Long-term results of this series show that the use of an RIC regimen with peripheral blood stem cells as the cell source, in children with high-risk leukemia who underwent haplo-PTCy has tolerable toxicity, universal engraftment, and good survival rates.

Exploration of the relationship between intestinal flora changes and gut acute graft-versus-host disease after hematopoietic stem cell transplantation

BACKGROUND

Acute graft-versus-host disease (aGVHD) is a life-threatening factor for post-hematopoietic stem cell transplantation (HSCT) patients. To investigate the relationship between intestinal flora changes and gut aGVHD after HSCT, we performed this cross-sectional study.

METHODS

We selected children from our medical center from July 2016 to January 2017. Fifty-six samples from 42 patients and 6 samples from normal children met the study criteria and were analyzed. Fecal 16S RNA sequencing was completed before transplantation or on days 7, 28 or 100 post-transplantation. The intestinal infection and GVHD clinical data were retrospectively analyzed, and the survival risk factors were analyzed. Correlation analysis was performed with the feces bioinformatic data.

RESULTS

The GVHD group alpha diversity was the lowest, which was significantly different than that of the non-diarrhea group (P value=0.032). A richer posttransplantation relative abundance of Moraxellaceae was conducive to survival, while that of Enterococcaceae and Alphaproteobacteria was not. Similarly, a rich relative abundance of Proteobacteria, Gammaproteobacteria and Odoribacteraceae in the intestinal flora before HSCT contributed to patient death thereafter. Regarding diarrhea, the GVHD group exhibited a richer Pasteurellales and Pasteurellaceae relative abundances, which showed strong correlations with diarrhea severity. Peptostreptococcaceae, Bifidobacteriales and Bifidobacteriaceae were richer in relative abundance in the intestinal infection group and correlated with pretransplant characteristics.

CONCLUSIONS

The gut microbiota diversity was lowest when gut aGVHD occurred, which was consistent with the clinically higher mortality rate and greater treatment difficulty. Pasteurellaceae played an important role in gut aGVHD and diarrhea severity. Bifidobacteriaceae led to infectious diarrhea after HSCT. Specific bacteria were biomarkers for survival: Moraxellaceae, Enterococcaceae and Alphaproteobacteria from the intestinal flora after HSCT and Proteobacteria, Gammaproteobacteria and Odoribacteraceae before HSCT.

Outcomes of Unmanipulated Haploidentical Transplantation Using Post-Transplant Cyclophosphamide (PT-Cy) in Pediatric Patients With Acute Lymphoblastic Leukemia

HLA-haploidentical transplantation (haplo-HCT) using post-transplantation-cyclophosphamide (PT-Cy) is a feasible procedure in children with malignancies. However, large studies on Haplo-HCT with PT-Cy for childhood acute lymphoblastic leukemia (ALL) are lacking. We analyzed haplo-HCT outcomes in 180 children with ALL. Median age was 9 years, and median follow-up was 2.7 years. Disease status was CR1 for 24%, CR2 for 45%, CR+3 for 12%, and active disease for 19%. All patients received PT-Cy day +3 and +4. Bone marrow (BM) was the stem cell source in 115 patients (64%). Cumulative incidence of 42-day engraftment was 88.9%. Cumulative incidence of day-100 acute graft-versus-host disease (GVHD) grade II-IV was 28%, and 2-year chronic GVHD was 21.9%. At 2 years, cumulative incidence of nonrelapse mortality (NRM) was 19.6%. Cumulative incidence was 41.9% for relapse and 25% for patients in CR1. Estimated 2-year leukemia free survival was 65%, 44%, and 18.8% for patients transplanted in CR1, CR2, CR3+ and 3% at 1 year for active disease. In multivariable analysis for patients in CR1 and CR2, disease status (CR2 [hazard ratio {HR} = 2.19; P = .04]), age at HCT older than 13 (HR = 2.07; P = .03) and use of peripheral blood stem cell (PBSC) (HR = 1.98; P = .04) were independent factors associated with decreased overall survival. Use of PBSC was also associated with higher NRM (HR = 3.13; P = .04). Haplo-HCT with PT-Cy is an option for children with ALL, namely those transplanted in CR1 and CR2. Age and disease status remain the most important factors for outcomes. BM cells as a graft source is associated with improved survival.

HLA-Haploidentical Family Donors: The New Promise for Childhood Acute Lymphoblastic Leukaemia?

Allogeneic haematopoietic stem cell transplantation (HSCT) is indicated in children with high-risk, relapsed or refractory acute lymphoblastic leukaemia (ALL). HLA-matched grafts from cord blood and stem cell repositories have allowed patients without suitable sibling donors to undergo HSCT. However, challenges in procuring matched unrelated donor (MUD) grafts due to high cost, ethnic disparity and time constraints have led to the exponential rise in the use of stem cells from human leukocyte antigen (HLA)-haploidentical family donors. Whilst HLA-haploidentical HSCT (hHSCT) performed in adult patients with acute leukaemia has produced outcomes similar to MUD transplants, experience in children is limited. Over the last 5 years, more data have emerged on hHSCT in the childhood ALL setting, allowing comparisons with matched donor transplants. The feasibility of hHSCT using adult family donors in childhood ALL may also address the ethical issues related to selection of minor siblings in matched sibling donor transplants. Here, we review hHSCT in paediatric recipients with ALL and highlight the emergence of hHSCT as a promising therapeutic option for patients lacking a suitable matched donor. Recent issues related to conditioning regimens, donor selection and graft-vs.-host disease prophylaxis are discussed. We also identify areas for future research to address transplant-related complications and improve post-transplant disease-free survival.

Haploidentical HSCT with post transplantation cyclophosphamide versus unrelated donor HSCT in pediatric patients affected by acute leukemia

T-cell replete hematopoietic stem cell transplantation (HSCT) from a haploidentical donor followed by high doses of cyclophosphamide has been demonstrated to provide the best chances of a cure for many children in need of an allograft but who lack both a sibling and an unrelated donor. In this study we retrospectively compared the outcome of pediatric patients undergoing T-replete haploidentical HSCT (Haplo) for acute leukemia with those undergoing transplantation from unrelated HLA-matched donor (MUD) and HLA mismatched unrelated donor (MMUD) from 2012 to 2017 at our Center. Both univariable and multivariable analyses showed similar 5-year overall survival rates for MUD, MMUD, and Haplo patients: 71% (95% CI 56-86), 72% (95% CI 55-90), and 75% (95% CI 54-94), respectively (p = 0.97). Haplo patients showed reduced event-free survival rates compared to MUD and MMUD patients: 30% (95% CI 12-49) versus 70% (95% CI 55-84) versus 53% (95% CI 35-73), respectively (p = 0.007), but these data were not confirmed by a multivariable analysis. Non-relapse mortality (NRM) and relapse incidence (RI) were similar for the three groups. Therefore, our data confirm that Haplo is a suitable clinical option for pediatric patients needing HSCT when lacking both an MUD and an MMUD donor.

Efficacy of Haploidentical Hematopoietic Stem Cell Transplantation Compared With Chemotherapy as Postremission Treatment of Children With Intermediate-risk Acute Myeloid Leukemia in First Complete Remission

BACKGROUND

The role of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for children with intermediate-risk acute myeloid leukemia (IR-AML) in first complete remission has been controversial. The present study compared the effect of chemotherapy with unmanipulated haplo-HSCT as treatment of patients with IR-AML in first complete remission (CR1).

PATIENTS AND METHODS

We retrospectively analyzed the outcomes of 80 children with IR-AML and compared the effects of chemotherapy (n = 47) with those of haplo-HSCT (n = 33) as treatment in CR1.

RESULTS

The 3-year overall survival, event-free survival (EFS), and cumulative incidence of relapse (CIR) was 85.4% ± 4.1%, 73.2% ± 5.0%, and 25.4% ± 4.5%, respectively. Compared with the chemotherapy group, the patients in the haplo-HSCT group had a lower CIR (P = .059) and better EFS (P = .108), but roughly equivalent overall survival (P = .841). Multivariate analysis revealed chemotherapy and minimal residual disease (MRD) of ≥ 10^-3 after induction therapy as independent risk factors affecting CIR and EFS. EFS (P = .045) and CIR (P = .045) differed significantly between the 2 treatment groups in patients with MRD of ≥ 10^-3 after induction therapy.

CONCLUSION

Haplo-HSCT might be a feasible option for children with IR-AML in CR1, especially for patients with MRD of ≥ 10^-3 after induction therapy.

Alogliptin attenuates cyclophosphamide-induced nephrotoxicity: a novel therapeutic approach through modulating MAP3K/JNK/SMAD3 signaling cascade

Cyclophosphamide (CP) is widely used as a chemotherapy against various types of cancers. However, CP is accompanied with multiple organ toxicity due to production of reactive oxygen species (ROS), induction of inflammation and consequently apoptosis. Alogliptin (Alo) is a dipeptidyl peptidase 4 (DPP-IV) inhibitor, which is booming as an antidiabetic agent. Interestingly, gliptins are currently studied for their counter-regulatory effects against oxidative stress and inflammation via multiple pathways, among which is the mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinase (JNK) pathway. This cascade can reduce inflammation via mitigating the activity of mothers against decapentaplegic homolog 3 (SMAD3) and c-Jun. However, Alo effect against CP-induced kidney injury has not been previously elucidated. This tempted us to investigate the possible beneficial effect of Alo against CP-induced kidney injury via modulating the MAP3K/JNK/SMAD3 signaling cascade. Thirty-two male Wistar rats were randomly allocated into four groups. CP-treated group received a single dose of CP (200 mg/kg; i.p.). Alo-treated group received Alo (20 mg/kg/day; p.o.) for 7 days with single CP injection on day 2. Marked decrease in renal injury was observed upon Alo treatment, as evidenced through declined serum kidney function markers, oxidative stress and apoptosis markers, MAP3K expression, phospho (p)-SMAD3, p-JNK, and p-c-Jun levels. These cellular effects were reflected in reduced transforming growth factor beta (TGF-β) and tumor necrosis factor alpha (TNF-α) fibrotic and inflammatory mediators, coinciding with improved histopathological portrait. In conclusion, the current study provides novel application of Alo as a therapeutic modality against CP-induced nephrotoxicity.

Hematopoietic Stem Cell Transplantation, Where Have We Come and Where Do We Go

Hematopoietic cellular transplantation (HCT) has impacted medicine beyond simply treating certain diseases. Allogeneic HCT was the first documented successful immunological cellular therapy. Its usage continues to increase. The immunological disparity between donor and recipient has been associated with better antitumor efficacy as well as immunological toxicities. Through active clinical trials and research, considerable improvements in HCT therapy have been made over the past 50 years. The HCT international outcomes registry has considerably contributed to these improvements by identifying factors that could never be studied by a single center. With the use of unrelated donors, international collaboration increased as donor cell access through registries was not inhibited by international boundaries. HCT as a field pioneered the development of organizations for self-regulation that were assessing the entire program as an integrated whole rather than simply assessing facilities and providers separately.

Co‑transplantation of tonsil‑derived mesenchymal stromal cells in bone marrow transplantation promotes thymus regeneration and T cell diversity following cytotoxic conditioning

Bone marrow (BM) transplantation (BMT) represents a curative treatment for various hematological disorders. Prior to BMT, a large amount of the relevant anticancer drug needed to be administered to eliminate cancer cells. However, during this pre-BMT cytotoxic conditioning regimen, hematopoietic stem cells in the BM and thymic epithelial cells were also destroyed. The T cell receptor (TCR) recognizes diverse pathogen, tumor and environmental antigens, and confers immunological memory and self-tolerance. Delayed thymus reconstitution following pre-BMT cytotoxic conditioning impedes de novo thymopoiesis and limits T cell-mediated immunity. Several cytokines, such as RANK ligand, interleukin (IL)-7, IL-22 and stem cell factor, were recently reported to improve thymopoiesis and immune function following BMT. In the present study, it was found that the co-transplantation of tonsil-derived mesenchymal stromal cells (T-MSCs) with BM-derived cells (BMCs) accelerated the recovery of involuted thymuses in mice following partial pre-BMT conditioning with busulfan-cyclophosphamide treatment, possibly by inducing FMS-like tyrosine kinase 3 ligand (FLT3L) and fibroblast growth factor 7 (FGF7) production in T-MSCs. The co-transplantation of T-MSCs with BMCs also replenished the CD3⁺ cell population by inhibiting thymocyte apoptosis following pre-BMT cytotoxic conditioning. Furthermore, T-MSC co-transplantation improved the recovery of the TCR repertoire and led to increased thymus-generated T cell diversity.

Allogeneic hematopoietic stem cell transplantation from a 2-HLA-haplotype-mismatched family donor for posttransplant relapse: a prospective phase I/II study

HLA haploidentical hematopoietic stem cell transplantation (HSCT), i.e., HSCT from a 1-HLA-haplotype-mismatched family donor, has been successfully performed even as a second transplantation for posttransplant relapse. Is the haploidentical the limit of HLA mismatches in HSCT? In order to explore the possibility of HLA-mismatched HSCT from family donors beyond haploidentical relatives, we conducted a prospective phase I/II study of 2-HLA-haplotype-mismatched HSCT (2-haplo-mismatch HSCT). We enrolled 30 patients with posttransplant relapse (acute myeloid leukemia: 18, acute lymphoblastic leukemia: 11, non-Hodgkin lymphoma: 1). 2-haplo-mismatch HSCT was performed as the second to sixth transplantations. The donors were siblings (n = 12), cousins (n = 16), and second cousins (n = 2). The conditioning regimen consisted of fludarabine, cytarabine, melphalan, low-dose anti-thymocyte globulin, and 3 Gy of total body irradiation. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus, methylprednisolone, and mycophenolate mofetil. All patients achieved neutrophil engraftment, except for a case of early death. The cumulative incidences of grades II-IV and III-IV acute GVHD were 36.7% and 16.7%, respectively. The overall survival at 1 year, relapse, and non-relapse mortality rates was 30.1%, 38.9%, and 44.3%, respectively. Considering the poor prognosis of posttransplant relapse, 2-haplo-mismatch HSCT can be an alternative option in a second or third transplantation.

T-Cell Replete Myeloablative Haploidentical Bone Marrow Transplantation Is an Effective Option for Pediatric and Young Adult Patients With High-Risk Hematologic Malignancies

Twenty-one pediatric and young adult patients (1.1-24.7 years) with hematologic malignancies underwent myeloablative T-cell replete haploidentical bone marrow transplant (haplo-BMT) between October 2015 to December 2019. Fifty-seven percent of the patients were ethnic or racial minorities. Thirteen patients had B-cell precursor acute lymphoblastic leukemia (B-ALL) with 10 receiving 1,200 cGy fractionated total body irradiation with fludarabine while the remaining 11 patients had targeted dose-busulfan, fludarabine, melphalan conditioning. Graft-vs.-host disease (GvHD) prophylaxis consisted of post-transplant cyclophosphamide (15 patients) or cyclophosphamide and bendamustine (six patients), with all patients receiving tacrolimus and mycophenolate mofetil. Twelve patients were in first or second remission at time of transplant with five in >2nd remission and four with measurable disease. Three patients had failed prior transplants and three CAR-T cell therapies. Only one patient developed primary graft failure but engrafted promptly after a second conditioned T-replete peripheral blood stem cell transplant from the same donor. An absolute neutrophil count of 0.5 × 109/L was achieved at a median time of 16 days post-BMT while platelet engraftment occurred at a median of 30 days. The cumulative incidence of grades III to IV acute GvHD and chronic GvHD was 15.2 and 18.1%, respectively. With a median follow-up of 25.1 months the relapse rate is 17.6% with an overall survival of 84.0% and a progression-free survival of 74.3%. The chronic graft-vs.-host-free relapse-free survival (CRFS) is 58.5% while acute and chronic graft-vs.-host-free relapse-free survival (GRFS) is 50.1%. Myeloablative conditioned T-replete haploidentical BMT is a viable alternative to matched unrelated transplantation for children and young adults with high-risk hematologic malignancies.

Haploidentical stem cell transplant with post-transplantation cyclophosphamide and mini-dose methotrexate in children

BACKGROUND

Haploidentical stem cell transplantation (haplo-SCT) is an option for patients without human leukocyte antigen-matched related or unrelated donor. Post-transplantation cyclophosphamide (PTCy) is an effective method of graft versus host disease (GVHD) prophylaxis and permits the use of T-cell replete grafts in settings were ex vivo manipulation is not feasible.

METHODS

A retrospective study among patients younger than 18 years, with a history of hematologic malignancies who underwent haplo-SCT between 2012 and 2016. All patients received a preparative regimen of fludarabine, busulfan, and 400 cGy total body irradiation or melphalan. Post-transplant GvHD prophylaxis consisted either of PTCy (50 mg/kg on Days + 3 and + 4) and cyclosporine (CSA) plus mycophenolate (MMF) (15 mg/kg/dose, thrice daily, per os), or mini-dose methotrexate (MTX; 5 mg/m² dose) on Days + 5, +7, +10, and + 15.

RESULTS

A total of 52 children were included, whose median age was 9 years (interquartile range, 4.9-14; range, 1.2-17 years), and 63% were males. The most common complications were cytomegalovirus reactivation (57%) and hemorrhagic cystitis (36%). The acute GVHD prophylaxis was PTCy, CSA, and mini-dose MTX in 42 (81%) patients, and 10 (19%) patients received PTCy, CSA, and MMF. The cumulative incidence of acute GvHD II-IV, acute GvHD III-IV, and chronic GvHD were 42%, 8.5%, and 19%, respectively. Grades I-IV acute GvHD occurred in 100% of the patients who received prophylaxis with CSA and MMF, and 62% who received CSA and mini-dose MTX (p = .055). The transplant-related mortality at 100 days was 18%. The 5-year overall and event-free survival were 59% and 57%, respectively.

CONCLUSIONS

Haplo-SCT with PT/Cy can be an available, safe, and feasible option for children with hematologic malignancies; meanwhile, the use of mini-dose of MTX was associated with lower rates of acute GVHD. However, our results require further support from prospective randomized studies to improve the efficacy of this prophylactic strategy.

Haploidentical- versus identical-sibling transplant for high-risk pediatric AML: A multi-center study

Background

Human leukocyte antigen‐identical sibling donor (ISD)‐hematopoietic stem cell transplantation (SCT) is a potentially curative treatment for high‐risk pediatric acute myeloid leukemia (AML). A haploidentical donor (HID) is readily available to almost all children. Previous studies have demonstrated that patients with HID‐SCT had similar outcomes compared to ISD‐SCT for pediatric and adult AML. However, the role of HID‐SCT in high‐risk pediatric AML is unclear.

Methods

To compare the overall survival of high‐risk AML children who underwent either HID‐SCT or ISD‐SCT, we analyzed 179 cases of high‐risk AML patients under 18 years of age treated with either ISD‐SCT (n = 23) or HID‐SCT (n = 156). Granulocyte colony‐stimulating factor plus anti‐thymocyte globulin‐based regimens were used for HID‐SCT. We also analyzed the subgroup data of AML patients at first complete remission (CR1) before SCT with known cytogenetic risk.

Results

The numbers of adverse cytogenetic risk recipients were 8 (34.8%) and 13 (18.8%) in the ISD‐SCT group and the HID‐SCT group, and the number of patients with disease status beyond CR1 were 6 (26.1%) and 14 (20.3%) in the two groups. The cumulative rates of grades II‐IV acute graft‐versus‐host disease (GVHD) were 13.0% in the ISD‐SCT group and 34.8% in the HID‐SCT group (P = 0.062), with a three‐year cumulative rates of chronic GVHD at 14.1% and 34.9%, respectively (P = 0.091). The relapse rate in the ISD‐SCT group was significantly higher than that in the HID‐SCT group (39.1% vs. 16.4%, P = 0.027); with non‐relapse mortality at 0.0% and 10.6% (P = 0.113), respectively. The three‐year overall survival rates were 73.0% for the ISD‐SCT group and 74.6% for the HID‐SCT group (P = 0.689). In subgroup analysis, the three‐year relapse rate in the ISD‐SCT group was higher than that in the HID‐SCT group (50.0% vs. 9.2%, P = 0.001) and the three‐year DFS in the ISD‐SCT group (50.0%) was lower than that in the HID‐SCT group (81.2%) (P = 0.021).

Conclusions

Unmanipulated HID‐SCT achieved DFS and OS outcomes comparable to those of ISD‐SCT for high‐risk pediatric AML patients with potentially higher rate but manageable GVHD.

Prevention and Treatment of Acute Graft-versus-Host Disease in Children, Adolescents, and Young Adults

Acute graft-versus-host disease (GVHD) continues to be a major cause of morbidity and mortality after allogeneic hematopoietic cell transplant (HCT) in pediatric patients (ie, children and adolescent and young adults) and limits broader application of the therapy. Pediatric HCT patients have faced major obstacles to access clinical trials that test new agents for GVHD prevention and treatment. According to a recent search, only 6 clinical trials of interventions for prevention or treatment of acute GVHD were conducted specifically in pediatric patients in the United States over the past decade, with 8 internationally. In this review, we summarize the studies that were performed and specifically enrolled and reported on pediatric patients after allogeneic HCT and provide a listing of studies currently under way.

Improved survival rate in T-cell depleted haploidentical hematopoietic cell transplantation over the last 15 years at a single institution

T-cell depletion of an HLA-haploidentical (haplo) graft is often used to reduce the risk of graft-versus-host disease (GVHD), but the lack of donor T cells in the infused product may lead to graft failure, slow T-cell reconstitution, infections, and relapse. More selective T-cell depletion targeting CD45RA can effectively deplete naïve T cells but preserve large numbers of memory T cells leading to robust engraftment of diverse T-cell populations and reduction of viremia in the early post-transplant period. Herein, we report the outcome of 143 pediatric and young adult hematologic malignancy patients receiving a first allogeneic hematopoietic cell transplantation (HCT) on 6 consecutive ex vivo T-cell depleted haploHCT protocols over the past 15 years at a single institution - including the first 50 patients on an active CD45RA-depleted haploHCT study in which patients also received NK-cells and pharmacological GvHD prophylaxis post transplant. Our data demonstrated an increase in the 3-year overall survival and event-free survival in non-chemorefractory recipients receiving CD45RA-depleted grafts (78.9% and 77.7%, respectively) compared to historic T-cell depleted haploHCT cohorts (46.7% and 42.7%, respectively, p=0.004, and 0.003). This improvement was primarily due to a reduction in transplant related mortality without significant increase in the rates of GVHD.

Choice of Donor Source and Conditioning Regimen for Hematopoietic Stem Cell Transplantation in Sickle Cell Disease

In the United States, one out of every 500 African American children have sickle cell disease (SCD), and SCD affects approximately 100,000 Americans. Significant advances in the treatment of this monogenetic disorder have failed to substantially extend the life expectancy of adults with SCD over the past two decades. Hematopoietic stem cell transplantation (HSCT) remains the only curative option for patients with SCD. While human leukocyte antigen (HLA) matched sibling HSCT has been successful, its availability is extremely limited. This review summarizes various conditioning regimens that are currently available. We explore recent efforts to expand the availability of allogeneic HSCT, including matched unrelated, umbilical cord blood, and haploidentical stem cell sources. We consider the use of nonmyeloablative conditioning and haploidentical donor sources as emerging strategies to expand transplant availability, particularly for SCD patients with complications and comorbidities who can undergo neither matched related transplant nor myeloablative conditioning. Finally, we show that improved conditioning agents have improved success rates not only in the HLA-matched sibling setting but also alternative donor settings.

Healthcare utilization and financial impact of acute-graft-versus host disease among children undergoing allogeneic hematopoietic cell transplantation

The impact of AGVHD on healthcare utilization and cost is not well described. In this retrospective single center cohort study of 240 pediatric patients, we analyzed cost, healthcare utilization and patient outcomes for the first year post-alloHCT. Costs were estimated from charges recorded in the Pediatric Health Information System database and the hospital's accounting system. The overall incidence of grade I-IV aGVHD was 40.4%. The incidence of grade I, grade II, and grade III-IV aGVHD was 6.6%, 16.2%, and 17.5%, respectively. The overall incidence of steroid refractory (SR)-aGVHD was 10.8%. The median number of days of hospitalization in the first year post-alloHCT was significantly higher for patients with aGVHD vs. no aGVHD: 113 days (range: 35-354 days) vs. 63 days (range: 25-298 days), p < 0.001. Patients with SR-aGVHD had increased hospitalization compared with the patients with steroid responsive aGVHD (152.8 ± 66.6days vs. 111.3 ± 59.3 days, p = 0.004), with associated increased alloHCT cost of ~$200,000. On multivariable analysis of risk factor for alloHCT cost, aGVHD, was associated with significantly higher cost ($141,094 [SE = 31247], p < 0.001). In summary, aGVHD and SR-aGVHD is associated with prolonged hospitalization and higher cost and inferior survival among children. Better aGVHD prevention strategies are desperately needed. Despite significant advances, lack of effective salvage regimens for SR-aGVHD remains a major concern.

Current status of umbilical cord blood transplantation in children

The first umbilical cord blood (UCB) transplantation was performed 30 years ago. UCB transplantation (UCBT) is now widely used in children with malignant and non-malignant disorders who lack a matched family donor. UCBT affords a lower incidence of graft-versus-host disease compared to alternative stem cell sources, but also presents a slower immune recovery and a high risk of infections if serotherapy is not omitted or targeted within the conditioning regimen. The selection of UCB units with high cell content and good human leucocyte antigen match is essential to improve the outcome. Techniques, such as double UCBT, ex vivo stem cell expansion and intra-bone injection of UCB, have improved cord blood engraftment, but clinical benefit remains to be demonstrated. Cell therapies derived from UCB are under evaluation as potential novel strategies to reduce relapse and viral infections following transplantation. In recent years, improvements within haploidentical transplantation have reduced the overall use of UCBT as an alternative stem cell source; however, each may have its relative merits and disadvantages and tailored use of these alternative stem cell sources may be the optimal approach.

Benefits and challenges with diagnosing chronic and late acute GVHD in children using the NIH consensus criteria

Chronic graft-versus-host disease (cGVHD) and late acute graft-versus-host disease (L-aGVHD) are understudied complications of allogeneic hematopoietic stem cell transplantation in children. The National Institutes of Health Consensus Criteria (NIH-CC) were designed to improve the diagnostic accuracy of cGVHD and to better classify graft-versus-host disease (GVHD) syndromes but have not been validated in patients <18 years of age. The objectives of this prospective multi-institution study were to determine: (1) whether the NIH-CC could be used to diagnose pediatric cGVHD and whether the criteria operationalize well in a multi-institution study; (2) the frequency of cGVHD and L-aGVHD in children using the NIH-CC; and (3) the clinical features and risk factors for cGVHD and L-aGVHD using the NIH-CC. Twenty-seven transplant centers enrolled 302 patients <18 years of age before conditioning and prospectively followed them for 1 year posttransplant for development of cGVHD. Centers justified their cGVHD diagnosis according to the NIH-CC using central review and a study adjudication committee. A total of 28.2% of reported cGVHD cases was reclassified, usually as L-aGVHD, following study committee review. Similar incidence of cGVHD and L-aGVHD was found (21% and 24.7%, respectively). The most common organs involved with diagnostic or distinctive manifestations of cGVHD in children include the mouth, skin, eyes, and lungs. Importantly, the 2014 NIH-CC for bronchiolitis obliterans syndrome perform poorly in children. Past acute GVHD and peripheral blood grafts are major risk factors for cGVHD and L-aGVHD, with recipients ≥12 years of age being at risk for cGVHD. Applying the NIH-CC in pediatrics is feasible and reliable; however, further refinement of the criteria specifically for children is needed.

Concise Review: Boosting T-Cell Reconstitution Following Allogeneic Transplantation-Current Concepts and Future Perspectives

Allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for a large number of malignant and nonmalignant (inherited) diseases of the hematopoietic system. Nevertheless, non‐HLA identical transplantations are complicated by a severe T‐cell immunodeficiency associated with a high rate of infection, relapse and graft‐versus‐host disease. Initial recovery of T‐cell immunity following HSCT relies on peripheral expansion of memory T cells mostly driven by cytokines. The reconstitution of a diverse, self‐tolerant, and naive T‐cell repertoire, however, may take up to 2 years and crucially relies on the interaction of T‐cell progenitors with the host thymic epithelium, which may be altered by GvHD, age or transplant‐related toxicities. In this review, we summarize current concepts to stimulate reconstitution of a peripheral and polyclonal T‐cell compartment following allogeneic transplantation such as graft manipulation (i.e., T‐cell depletion), transfusion of ex vivo manipulated donor T cells or the exogenous administration of cytokines and growth factors to stimulate host‐thymopoiesis with emphasis on approaches which have led to clinical trials. Particular attention will be given to the development of cellular therapies such as the ex vivo generation of T‐cell precursors to fasten generation of a polyclonal and functional host‐derived T‐cell repertoire. Having been tested so far only in preclinical mouse models, clinical studies are now on the way to validate the efficacy of such T‐cell progenitors in enhancing immune reconstitution following HSCT in various clinical settings. stem cells translational medicine2019;00:1–8

Impacts of post-transplantation cyclophosphamide treatment after allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia

Post-transplant cyclophosphamide has become a promising medical option after allogeneic HSCT. In this study we aimed to evaluate the efficacy of cyclophosphamide and cyclosporine combination in acute and chronic graft-versus-host disease (GvHD) prophylaxis in acute myeloid leukemia (AML) cases scheduled for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Retrospective analysis of data from 40 cases who underwent allogeneic HSCT under GvHD prophylaxis with cyclophosphamide and cyclosporine combination between April 2016 and August 2017 was made. Cyclophosphamide was given at daily doses of 50 mg/kg on post-transplant 3^rd and 4^th days, and cyclosporine was applied at daily doses of 3 mg/kg/day starting from the 5^th post-transplant day. Cyclosporine dose was tapered beginning from the 45^th postoperative day and completely discontinued on the 90^th post-transplant day. Mean age was 38.25 ± 15.25 years. Posttransplant median follow-up was six months (6–17 months). Post-transplant, the number of deaths and mortality rates related and unrelated to transplantation were 5 (12.5%), and 2 (5%), respectively. Acute GvHD was diagnosed in 7 cases (17.5%), and relapse was noted in 9 cases (22.5%). Myeloablative or reduced intensity conditioning was performed in 22 (55%) and 18 (45%) patients, respectively. The distribution of the donors was as follows: match-related (n = 26; 65%), match-unrelated (n = 9, 22.5%) and haploidentical donors (n = 5; 12.5%). There was no statistically significant correlation between the transplant-related and unrelated mortality and parameters under investigation.Cyclophosphamide use appears to be a highly effective and promising strategy for acute GvHD prophylaxis in non-haploidentical allogeneic HSCT cases. Identification of the impact of cyclophosphamide use on the development of chronic GvHD needs further investigation.

Unrelated donor vs HLA-haploidentical α/β T-cell- and B-cell-depleted HSCT in children with acute leukemia

Traditionally, hematopoietic stem cell transplantation (HSCT) from both HLA-matched related and unrelated donors (UD) has been used for treating children with acute leukemia (AL) in need of an allograft. Recently, HLA-haploidentical HSCT after αβ T-cell/B-cell depletion (αβhaplo-HSCT) was shown to be effective in single-center studies. Here, we report the first multicenter retrospective analysis of 127 matched UD (MUD), 118 mismatched UD (MMUD), and 98 αβhaplo-HSCT recipients, transplanted between 2010 and 2015, in 13 Italian centers. All these AL children were transplanted in morphological remission after a myeloablative conditioning regimen. Graft failure occurred in 2% each of UD-HSCT and αβhaplo-HSCT groups. In MUD vs MMUD-HSCT recipients, the cumulative incidence of grade II to IV and grade III to IV acute graft-versus-host disease (GVHD) was 35% vs 44% and 6% vs 18%, respectively, compared with 16% and 0% in αβhaplo-HSCT recipients (P < .001). Children treated with αβhaplo-HSCT also had a significantly lower incidence of overall and extensive chronic GVHD (P < .01). Eight (6%) MUD, 32 (28%) MMUD, and 9 (9%) αβhaplo-HSCT patients died of transplant-related complications. With a median follow-up of 3.3 years, the 5-year probability of leukemia-free survival in the 3 groups was 67%, 55%, and 62%, respectively. In the 3 groups, chronic GVHD-free/relapse-free (GRFS) probability of survival was 61%, 34%, and 58%, respectively (P < .001). When compared with patients given MMUD-HSCT, αβhaplo-HSCT recipients had a lower cumulative incidence of nonrelapse mortality and a better GRFS (P < .001). These data indicate that αβhaplo-HSCT is a suitable therapeutic option for children with AL in need of transplantation, especially when an allele-matched UD is not available.

Favorable Outcome of Post-Transplantation Cyclophosphamide Haploidentical Peripheral Blood Stem Cell Transplantation with Targeted Busulfan-Based Myeloablative Conditioning Using Intensive Pharmacokinetic Monitoring in Pediatric Patients

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplantation cyclophosphamide (PTCy) was performed previously in adults using a nonmyeloablative conditioning regimen and bone marrow as a graft source. In an effort to reduce relapse rates, myeloablative conditioning regimens with higher intensities are now used. We used an intensive daily pharmacokinetic monitoring method for busulfan dosing in children for effective myeloablation and to reduce toxicity. Here, we report the retrospective results of 34 patients (median age 11.1 years) who underwent haplo-HSCT with PTCy using a targeted busulfan-based myeloablative conditioning regimen and peripheral blood as a stem cell source. The donor-type neutrophil engraftment rate was 97.1%, and the cumulative incidence rates of grade II to IV and grade III to IV acute and extensive chronic graft-versus-host disease were 38.2%, 5.9%, and 9.1%, respectively. The overall survival and event-free survival rates, and treatment-related mortality were 85.0%, 79.4%, and 2.9%, respectively. Based on the subgroup analysis of patients with malignancies (n = 23), the relapse incidence rate was 21.7%. Haplo-HSCT using PTCy with targeted busulfan-based myeloablative conditioning and peripheral blood as a stem cell source was a safe and promising therapeutic option for children.