Halfway there: the past, present and future of haploidentical transplantation.

In recent years, the use of haploidentical donors for hematopoietic cell transplantation has expanded rapidly. Approximately 50% of patients requiring hematopoietic cell transplant lack a traditional donor. The use of HLA haploidentical-related donors is attractive due to nearly universal availability of this graft source. We summarize the current and future need for haploidentical donors and detail the rise of post-transplant cyclophosphamide as the dominant haploidentical approach. Further, we examine ongoing controversies in the field of haploidentical transplant, including conditioning regimens and graft source. Finally, we review the evidence available from preliminary comparative studies and discuss future direction of research.