Phase I/II Pilot Study of Mixed Chimerism to Treat Hemoglobinopathies

Hematopoietic stem cell transplantation (HSCT) is emerging as a therapeutic alternative for patients with sickle cell disease. Conventional HSCT therapy has been limited to extremely high-risk hemoglobinopathy patients. Those patients who may be difficult to identify before end-organ damage develops. Also, conventional HSCT is only available to the minority of candidates who have Histocompatibility Leukocyte Antigen (HLA) identical siblings to donate bone marrow or mobilized peripheral blood stem cells. This study proposes two important improvements over conventional HSCT: * Donor peripheral blood or bone marrow will be processed via a new technology, which will deplete mature immune cells while enriching hematopoietic stem cells (HSC) and graft facilitating cells (FC). * A reduced intensity recipient conditioning regimen will be used to promote mixed allogeneic chimerism, as opposed to full donor chimerism, following HSCT. These two elements may significantly improve the benefit:risk ratio of HSCT for patients with hemoglobinopathies. Stem cell transplantation may become a more feasible option for patients that do not have HLA-identical siblings that can donate stem cells. Also, transplantation may be offered to patients earlier in the disease progression, before end-organ damage occurs.