Outcomes of Unrelated Donor Stem Cell Transplantion with Post-Transplant Cyclophosphamide for Graft-versus-Host Disease Prophylaxis in Patients with Severe Sickle Cell Disease.

Unrelated donor (URD) hematopoietic cell transplantation (HCT) in children with sickle cell disease (SCD) is associated with a high incidence of rejection and graft-versus-host disease (GVHD). We report on the first 4 patients with severe SCD who underwent URD HCT using a novel myeloablative and immunosuppressive regimen composed of busulfan, fludarabine, and antithymocyte globulin with a single dose of post-transplant cyclophosphamide along with tacrolimus and mycophenolate mofetil for GVHD prophylaxis. Three patients engrafted and remain disease-free after a median follow-up period of 2.5 years. One patient had primary graft failure attributed to low stem cell content of the graft. Of interest, none of the engrafted patients developed acute or chronic GVHD. This preparative regimen along with the use of post-transplant cyclophosphamide offers a promising approach for unrelated donor transplants in patients with SCD and needs further corroboration in larger number of patients.