A Pilot Study of HSCT for Patients With High-risk Hemoglobinopathy Using a Nonmyeloablative Preparative Regimen

Hypothesis 1: A novel nonmyeloablative condition regimen will be safe and efficacious in producing stable donor chimerism and cure of severe hemoglobinopathy. Hypothesis 2: Stable donor chimerism will result in amelioration of cerebral vasculopathy, improved cerebral perfusion and neurocognitive function. Specific Aim 1: Study the safety and efficacy of a novel non-toxic conditioning regimen for HSCT for patients with severe hemoglobinopathies and the kinetics of lineage specific chimerism after HSCT We will test our hypothesis that a novel nonmyeloablative condition regimen will be safe and efficacious in producing stable donor chimerism and cure of severe hemoglobinopathy: Specific Aim 2: Optimize the immunosuppressive regimen for HSCT patients through a thorough understanding of the pharmacokinetics of Busulfan (BU) and mycophenolate mofetil (MMF) in the patient population. This will involve: 1. Determine the pharmacokinetics of intravenously and orally administered MMF and intravenous BU in patients receiving HSCT. 2. Determine the relationship of Area under the curve (AUC) of BU and mean trough concentrations of mycophenolic acid (MPA) to engraftment and graft versus host disease (GVHD). 3. Determine the relationship of Area under the curve (AUC) and steady state concentration of BU to engraftment at day 30 and 1 year post HSCT. Specific Aim 3: Study the effect of complete or partial donor chimerism on silent and overt cerebral vasculopathy, and neurocognitive functioning in patients with SCD undergoing HSCT. We will test our hypothesis that stable donor chimerism will result in improvement in cerebral vasculopathy and neurocognitive function. This will include. 1. Determine effect of transplantation silent and overt cerebral vasculopathy by comparison MRA and TCD 1 year after HSCT to pre-HSCT studies. 2. Determine effect on HSCT on neurocognitive function. Specific Aim 4: To determine the rate of T cell immune reconstitution in children with sickle cell