RecruitingPhase 1Biological interventionHaploidentical Transplantation With Pre-Transplant Immunosuppressive Therapy for Patients With Sickle Cell DiseaseThis is a study to evaluate the safety and toxicity of a treatment regimen consisting of 2 cycles of pre-transplant immunosuppressive therapy followed by myeloablative preparative regimen and allogeneic hematopoietic stem cell transplantation from a haploidentical donor in patients with sickle cell disease. The overall goal of this study is to expand the donor pool for hematopoietic stem cell transplantation in sickle cell disease using haploidentical donors, and to develop a non-toxic, myeloablative regimen, with the goal of achieving a consistent donor chimerism utilizing pre-transplant immunosuppressive therapy.