Christopher Kanakry, MD, Center for Cancer Research, National Cancer Institute, Bethesda, MD, discusses optimizing timing of post-transplantation cyclophosphamide in MHC-haploidentical murine hematopoietic cell transplantation (HSCT). This interview was recorded at the 5th International Congress on Controversies in Stem Cell Transplantation and Cellular Therapies (COSTEM) 2019, held in Berlin, Germany.