Haploidentical peripheral blood stem cell transplantation with posttransplant cyclophosphamide in children and adolescents with hematological malignancies

Lesson learned in pediatric haploidentical transplantation in a low-resource environment: delivering melphalan IV and using low dose radiation reduce graft failure

Objectives: Primary graft failure (pGF) after hematopoietic stem-cell transplant is associated with considerable morbidity and mortality. The incidence in haplo-HSCT has been reported to be between 0% and 30%. In 2018, we identified a pGF incidence of 35% in our pediatric haplo-HSCT recipients with hematologic malignancies, which motivated us to enact changes to the conditioning regimen.Methods: We performed a single-center prospective, pre-post study of consecutive patients under 16 years with hematologic malignancies, from January 2015 to December 2022 who received a haplo-HSCT. Twenty-six pediatric patients received a haplo-HSCT before September 2018 (G1) and 36 patients after (G2). The main conditioning regimen for G1 was myeloablative with Flu/Cy/Bu, and for G2 the main regimen was reduced intensity Flu/Cy/Mel/TBI2.Results: Nine patients (35%) in G1 had primary graft failure, while in G2 there were no patients with pGF. The median follow-up for G1 was 15.9 months, and for G2 was 24.8 months, with an estimated overall survival at 12 months of 63% (95% CI 47-76) versus 85% (95% CI 73-93), and at 24 months of 47% (95% CI 31-64) versus 70% (95% CI 54-82) respectively (p = .007).Conclusion: After September 2018 conditioning regimen modifications were implemented with the objective of reducing primary failure, consisting mainly of switching from busulfan to melphalan as the alkylating agent of choice, and adding, when clinically possible TBI. Primary failure has been significantly reduced in our institution since then.

More about post-transplant cyclophosphamide in haploidentical grafts: full or reduced doses?

Haploidentical hematopoietic can be conducted on an outpatient basis but the two main reasons to accept into the hospital a patient in this setting are complications of the hematological toxicity and/or the cytokine-release syndrome. With the aim of reducing the post-transplant cyclophosphamide-dependent toxicity without compromising its effectivity, attempts to reduce the dose of post-transplant cyclophosphamide have been made: Decreases from the conventional total dose of post-transplant cyclophosphamide (100 mg/Kg) have been explored worldwide, showing that decreasing the total dose to even 50 mg/Kg significantly decreases the toxicity of the procedure without compromising its efficacy, safety and results. We present here the salient data of the attempts to diminish the doses of post-transplant cyclophosphamide which have been done and published worldwide, information that suggests that the conventional doses of post-transplant cyclophosphamide can be significantly reduced thus decreasing the toxicity, without compromising the effectiveness of the procedure, mainly the development of graft versus host disease.

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.

Haploidentical vs. HLA-matched donor hematopoietic stem-cell transplantation for pediatric patients with acute lymphoblastic leukemia in second remission: A collaborative retrospective study of the Spanish Group for Bone Marrow Transplantation in Children (GETMON/GETH) and the Spanish Childhood Relapsed ALL Board (ReALLNet)

Introduction

Studies addressing the role of haploidentical as alternative to HLA-matched donors for stem cell transplantation (SCT) often include patients with diverse hematological malignancies in different remission statuses.

Methods

We compared outcomes of children with acute lymphoblastic leukemia (ALL) undergoing SCT in second complete remission (CR2) from haploidentical (n = 25) versus HLA-matched donor (n = 51).

Results

Patients were equally distributed across both groups according to age, immunophenotype, time to and site of relapse, relapse risk-group allocation, and minimal residual disease (MRD) before SCT. Incidence of graft failure, acute graft versus host disease (GVHD), and other early complications did not differ between both groups. We found no differences in overall survival (58.7% versus 59.5%; p = .8), leukemia free survival (LFS) (48% versus 36.4%; p = .5), event free survival (40% versus 34.4%; p = .69), cumulative incidence (CI) of subsequent relapse (28% versus 40.9%; p = .69), treatment related mortality (24% versus 23.6%; p = .83), CI of cGVHD (4.5% versus 18.7%; p = .2), and chronic GVHD-free and leukemia-free survival (44% versus 26.3%; p = .3) after haploidentical donor SCT. Chronic GVHD (HR = 0.09; p=.02) had protective impact, and MRD ≥ 0.01% before SCT (HR = 2.59; p=.01) had unfavorable impact on LFS.

Discussion

These results support the role of haploidentical donor SCT in children with ALL in CR2.

Conducting hematopoietic stem cell transplantation in low and middle income countries

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is a well-recognized therapeutic procedure; costs limit its widespread use in low and middle income countries (LMIC).

METHODS

Over a 30-year period, we have conducted HSCT in LMIC, making adaptations to the conventional procedures conducted in high-income countries (HIC).

RESULTS

These salient observations stem from our practice: (1) Start with autologous transplantations in patients with hematological malignancies, specifically multiple myeloma; cell freezing devices are not necessary. (2) Next, consider auto-HSCT in patients with autoimmune diseases. (3) Introduce allogeneic transplants, initially using reduced intensity conditioning regimens. Conducting the HSCT on an outpatient basis is cheaper and safer. (4) Do not build HEPA-filtered rooms nor laminar flow cabins. (5) Do not graft cord blood cells nor start a cord blood blank. (6) Engage in haploidentical transplantations which are more feasible and cost-effective. (7) Matched unrelated donors are extremely expensive. (8) Use generic drugs and biosimilars. (9) Blood product irradiation devices are not necessary. (10) Do not try to reproduce other HSCT programs from HIC; develop your own methods.

CONCLUSIONS

HSCT can be conducted in LMIC with reduced costs and similar efficacy, thus making this therapeutic option affordable for more persons.

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.

Sub-myeloablative Second Transplantations with Haploidentical Donors and Post-Transplant Cyclophosphamide have limited Anti-Leukemic Effects in Pediatric Patients

Pediatric patients with high-risk hematologic malignancies who experience relapse after a prior allogeneic hematopoietic cell transplant (HCT) have an exceedingly poor prognosis. A second allogeneic HCT offers the potential for long-term cure but carries high risks of both subsequent relapse and HCT-related morbidity and mortality. Using haploidentical donors for HCT (haploHCT) can expand the donor pool and potentially enhance the graft-versus-leukemia effect but is accompanied by a risk of graft-versus-host disease (GVHD). The goal of this protocol was to intensify the antileukemia effect of haploHCT for pediatric patients with hematologic malignancies that relapsed after prior allogeneic HCT, while limiting regimen-associated toxicities. This phase II clinical trial evaluated a sub-myeloablative preparative regimen consisting of anti-thymocyte globulin, clofarabine, cytarabine, busulfan, and cyclophosphamide, in combination with plerixafor to sensitize leukemic blasts. Participants received a mobilized peripheral blood unmanipulated haploidentical donor graft with one dose of post-transplant cyclophosphamide as GVHD prophylaxis, followed by natural killer (NK) cell addback. Here we report the clinical outcomes and immune reconstitution of 17 participants treated on the study and 5 additional patients treated on similar single-patient treatment plans. Of the 22 participants analyzed, 12 (55%) had active disease at the time of HCT. The regimen provided robust immune reconstitution, with 21 participants (95%) experiencing neutrophil engraftment at a median of 14 days after HCT. In this high-risk population, the overall survival was 45% (95% confidence interval [CI], 24%-64%), with a 12-month event-free survival of 31% (95% CI, 14%-51%) and cumulative incidence of relapse at 12 months of 50% (95% CI, 27%-69%). Four participants (18%) remain in remission at >5 years follow-up. Expected HCT-related organ-specific toxicities were observed, and 13 participants (59%) experienced acute or chronic GVHD. This intensified but sub-myeloablative regimen, followed by a high-dose unmanipulated haploidentical graft, post-transplantation cyclophosphamide, and NK cell infusion, resulted in adequate immune reconstitution but failed to overcome the elevated risks of relapse and treatment-related morbidity in this high-risk population.

Perspectives on establishing a public cord blood inventory in South Africa

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

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.

Concordant acute myeloblastic leukemia in identical twins treated with allogeneic transplantation from a younger HLA-identical sibling following a single apheresis procedure

A concordant leukemia is that which occurs in a pair of monozygotic twins; a similar genetic background suggests an in utero monoclonal origin. We present the case of a pair of monozygotic infants with concordant acute myeloid leukemia who underwent a peripheral blood hematopoietic stem-cell transplant (HSCT) from a single, younger human leukocyte antigen-identical sibling donor, using a fractioned graft collected during only one apheresis procedure. Twin A relapsed at +456 and received a second haploidentical HSCT from his father, twin B has been in complete remission since the first HSCT. Both children are in complete remission and with negative minimal residual disease at +900 (after second transplant) and +1488, respectively.

Haploidentical transplantation in high-risk pediatric leukemia: A retrospective comparative analysis on behalf of the Spanish working Group for bone marrow transplantation in children (GETMON) and the Spanish Grupo for hematopoietic transplantation (GETH)

A total of 192 pediatric patients, median age 8.6 years, with high-risk hematological malignancies, underwent haploidentical stem cell transplantation (haplo-HSCT) using post-transplantation cyclophosphamide (PT-Cy), or ex vivo T cell-depleted (TCD) graft platforms, from January 1999 to December 2016 in 10 centers in Spain. Some 41 patients received an unmanipulated graft followed by PT-Cy for graft-vs-host disease (GvHD) prophylaxis. A total of 151 patients were transplanted with CD3-depleted peripheral blood stem cells (PBSCs) by either CD34⁺ selection, CD3⁺ CD19⁺ depletion, TCRαβ⁺ CD19⁺ depletion or CD45RA⁺ depletion, added to CD34⁺ selection for GvHD prophylaxis. The PBSCs were the only source in patients following ex vivo TCD haplo-HSCT; bone marrow was the source in 9 of 41 patients following PT-CY haplo-HSCT. Engraftment was achieved in 91.3% of cases. A donor younger than 30 years, and the development of chronic GvHD were positive factors influencing survival, whereas positive minimal residual disease (MRD) before transplant and lymphoid disease were negative factors. The probability of relapse increased with lymphoid malignancies, a donor killer-cell immunoglobulin-like receptor (KIR) haplotype A and positive MRD pretransplant. No difference was found in overall survival, disease-free survival or relapse incidence between the two platforms. Relapse is still of concern in both platforms, and it should be the focus of future efforts. In conclusion, both platforms for haplo-HSCT were effective and could be utilized depending on the comfort level of the center.

Granulocyte Colony-Stimulating Factor-Primed Unmanipulated Haploidentical Blood and Marrow Transplantation

Granulocyte colony-stimulating factor (G-CSF), a growth factor for neutrophils, has been successfully used for stem cell mobilization and T cell immune tolerance induction. The establishment of G-CSF-primed unmanipulated haploidentical blood and marrow transplantation (The Beijing Protocol) has achieved outcomes for the treatment of acute leukemia, myelodysplastic syndrome, and severe aplastic anemia with haploidentical allografts comparable to those of human leukocyte antigen (HLA)-matched sibling donor transplantation. Currently, G-CSF-mobilized bone marrow and/or peripheral blood stem cell sources have been widely used in unmanipulated haploidentical transplant settings. In this review, we summarize the roles of G-CSF in inducing T cell immune tolerance. We discuss the recent advances in the Beijing Protocol, mainly focusing on strategies that have been used to improve transplant outcomes in cases of poor graft function, virus infections, and relapse. The application of G-CSF-primed allografts in other haploidentical modalities is also discussed.

Cyclosporine A for the Prevention of Ocular Graft versus Host Disease in Allogeneic Hematopoietic Stem Cell Transplant Recipients Is Safe and Feasible

PURPOSE

To evaluate the safety and efficacy of ocular cyclosporine in the prevention of the development of ocular graft versus host disease (oGVHD) in patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT) in comparison with historic data.

DESIGN

We developed a longitudinal, observational, prospective nonrandomized study. We evaluated the feasibility of prophylactic use of topical cyclosporine A (CsA) to prevent or decrease the incidence of oGVHD and compared this with historic data.

METHODS

Patients undergoing AHSCT were treated with prophylactic topical CsA for 12 months after engraftment, followed by serial ophthalmic evaluations, including the Schirmer test.

RESULTS

Twenty patients were included. No serious adverse effects were reported. Poor adherence was documented in 15% of patients. In spite of observing extra-ocular GVHD (acute and chronic GVHD incidence of 50 and 45%, respectively), only 1 in 20 patients developed oGVHD over the 20-month follow-up for the entire cohort. No statistically significant difference was observed in the incidence of oGVHD when compared to a historical cohort.

CONCLUSIONS

Topical CsA as a prophylactic measure for oGVHD, administered over a period of 1 year after grafting, is safe and feasible and may decrease the incidence of ophthalmic manifestations of GVHD. These findings must be confirmed in a randomized trial.