It has been extremely difficult to find a curative therapy for those with severe sickle cell disease (SCD) who doesn’t have an HLA-identical sibling donor. A multi-institutional learning collaborative was created as part of a Phase II clinical trial of nonmyeloablative, related HLA-haploidentical (haplo) bone marrow transplantation (BMT) with post-transplantation cyclophosphamide in order to enhance engraftment while reducing transplantation-related morbidity. All eligible subjects had haemoglobin SS, and 16 out of 18 had a donor who could be identified in 89 percent of cases. Overt stroke was the most frequent reason for transplantation, with a median patient age of 20.9 years. Antithymocyte globulin, fludarabine, cyclophosphamide, and low-dose total body irradiation made up the first 3 patients’ conditioning regimen. Following transplantation, cyclophosphamide, mycophenolate mofetil, and sirolimus were used as graft-versus-host disease (GVHD) prevention. Initial graft two of the three patients (or 67%) had rejection, which led to the study-stopping rule being activated.