Abatacept for GVHD Prophylaxis After Hematopoietic Stem Cell Transplantation for Pediatric Sickle Cell Disease

Outcomes of hematopoietic stem cell transplantation (HSCT) for children and adolescents with sickle cell disease (SCD) have improved. Graft versus host disease (GVHD), however, remains a barrier to success. GVHD accounts for most of the transplant related mortality and much of the morbidity in this setting-in part through the injury it directly causes and in part through the deleterious effects of steroids and the other immunosuppressive agents used to prevent and treat it. The results of pre-clinical studies and a phase I clinical study in patients with hematologic malignancies suggest that the costimulation blocking agent CTLA4-Ig may hold promise an agent for GVHD prophylaxis. In the present trial, the investigators are assessing the tolerability of adding abatacept to standard GVHD prophylaxis-a calcineurin inhibitor and methotrexate-in pediatric SCD patients receiving early alemtuzumab (completed by day -18) followed by fludarabine, thiotepa, and melphalan for conditioning. This trial will provide the foundation for subsequent trials designed to test the long-term hypothesis that abatacept is a safe, steroid-sparing effective adjunct to standard GVHD prophylaxis in this setting.