HLA-haploidentical stem cell transplantation -current trends and issues-

Abstract

Allogeneic hematopoietic stem cell transplantation is a potentially curative treatment for patients with hematological malignancies and nonmalignant diseases. HLA-matched related or unrelated donors are the first choice but are not always available for all patients. Alternative donors who share a single HLA haplotype (HLA-haploidentical donors) with recipients are nearly always available, but HLA-haploidentical stem cell transplantation is associated with high incidences of graft-versus-host disease (GVHD) and graft rejection. Over the last few decades, several strategies have been developed to overcome HLA barriers. The most popular strategy has been T cell depletion of stem cell grafts; ex vivo T-cell depletion by CliniMACS®; in vivo T-cell depletion by antithymocyte globulin or alemtuzumab. However, these strategies are associated with an increased risk of severe opportunistic infections and nonrelapse mortality. More recently, T cell replete haploidentical transplantation has been developed by using post-transplant cyclophosphamide. The rationale of this strategy is selective depletion of alloreactive T cells. The incidence of acute GVHD, chronic GVHD, and NRM after PTCy-based haploidentical stem cell transplantation appears to be equivalent to those after HLA-matched stem cell transplantation. Together with progress of these platforms, HLA-haploidentical transplantation is becoming a novel breakthrough.