Optimal dose of rabbit thymoglobulin in conditioning regimens for unmanipulated, haploidentical, hematopoietic stem cell transplantation: Long-term outcomes of a prospective randomized trial

Reduced-Intensity Conditioning and Dual T Lymphocyte Suppression with Antithymocyte Globulin and Post-Transplant Cyclophosphamide as Graft-versus-Host Disease Prophylaxis in Haploidentical Hematopoietic Stem Cell Transplants for Hematological Malignancies

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HaploHSCT after RIC with ATG, PTCy, and cyclosporine is a feasible transplant regimen.

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Low rates of grade II to IV acute GVHD were observed.

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ATG use leads to higher rates of viral reactivation, particularly CMV and EBV.

Haploidentical hematopoietic stem cell transplantation (haploHSCT) with conditioning regimens using post-transplant cyclophosphamide (PTCy) for peripheral blood stem cell (PBSC) grafts is limited by comparably higher rates of acute and chronic graft-versus-host disease (GVHD). Antithymocyte globulin (ATG) may mitigate this risk. We evaluated haploHSCT after reduced-intensity conditioning (RIC) with ATG, PTCy, and cyclosporine to prevent rejection and GVHD. Fifty adults underwent haploHSCT from August 2016 to February 2018. RIC included fludarabine (30 mg/m²/day on days –5 to –2), busulfan (3.2 mg/m²/day on days –3 and –2), and total body irradiation (200 cGy) on day –1. Unmanipulated PBSCs were infused on day 0. GVHD prophylaxis included ATG (4.5 mg/kg over days –3 to –1), PTCy (50 mg/kg/day on days +3 and +4), and cyclosporine from day +5. Median age was 56 years (range, 22 to 70 years); 25 (73.5%) patients were in first complete remission (CR1), 5 (14.7%) were in second complete remission (CR2), and 8 (23.5%) had active disease. Median time to neutrophil engraftment was 16 days (range, 8 to 43 days). At day +100, the cumulative incidence of acute GVHD of any grade, and grades III to IV was 38.3% and 5.2%, respectively. Mild chronic GVHD was seen in 15.5%. Cytomegalovirus (CMV) reactivation occurred in 37 (74%) cases and CMV disease occurred in 4 (11.5%) cases. Epstein-Barr virus (EBV) reactivation occurred in 21 (61.8%) patients. The incidence of histologically confirmed post-transplantation lymphoproliferative disorder (PTLD) was 5.8%. Four patients received rituximab. There were no CMV, EBV, or PTLD-related deaths. Six-month and 1-year overall survival (OS), cumulative incidence of relapse (CIR), and nonrelapse mortality (NRM) were 73.9%, 10.2%, and 19.4%, respectively, and 48.1%, 16% and 38.2%, respectively. Infection was the most common cause of death (18%). Unmanipulated haploidentical PBSC transplantation following RIC with ATG, PTCy, and cyclosporine as a GVHD prevention strategy results in low rates of acute and chronic GVHD.

Update on current research into haploidentical hematopoietic stem cell transplantation

INTRODUCTION

Haploidentical stem cell transplantation (Haplo-SCT) is currently a suitable alternative worldwide for patients with hematological diseases, who lack human leukocyte antigen (HLA)-matched siblings or unrelated donors. Areas covered: This review summarizes the advancements in Haplo-SCT in recent years, primarily focusing on the global trends of haploidentical allograft, the comparison of outcomes between Haplo-SCT and other transplantation modalities, strategies for improving clinical outcomes, including donor selection, hematopoietic reconstitution promotion, and graft-versus-host disease, and relapse prevention/management, as well as the expanded indications of Haplo-SCT, such as severe aplastic anemia, myeloma and lymphoma. Expert commentary: Haploidentical allografts, including granulocyte colony-stimulating factor-based protocol and a post-transplant cyclophosphamide-based protocol, have been the mainstream strategy for Haplo-SCT. However, there are many unanswered questions in this field.