A Study of Immune Suppression Treatment for People With Sickle Cell Disease or β-Thalassemia Who Are Going to Receive an Allogeneic Hematopoietic Cell Transplantation (HCT)

Hematopoietic Cell Transplantation/HCT involves receiving healthy blood-forming cells (stem cells) from a donor to replace the diseased or damaged cells in participants' bone marrow. The researchers think giving participants treatment with fludarabine and dexamethasone, drugs that lower the activity of the body's immune system (immune suppression), before standard conditioning therapy and HCT may help prevent serious side effects, including graft failure and GvHD. In this study, depending on how participants' body responds to the fludarabine and dexamethasone, the study doctor may decide participants should receive another drug, called cyclophosphamide, instead of fludarabine. In addition, depending on the results of participants' routine blood tests, participants may receive the drugs bortezomib and rituximab, which also help with immune suppression.