National Heart, Lung, and Blood Institute is conducting a Non-Randomized trial in 150 participants in order to explore the use of a Bone Marrow Transplant regimen that, instead of chemotherapy, uses a low dose of radiation, combined with two immunosuppressive drugs.
Nonmyeloablative allogeneic peripheral blood stem cell (PBSC) transplants are currently being investigated in phase I/II trials assessing engraftment, efficacy, and toxicity at a number of transplant centers. Preliminary data have shown a high rate of complete donor engraftment with a relatively low toxicity profile.
The decreased risk of transplant-related complications associated with nonmyeloablative transplants expands eligibility to patients with nonmalignant hematological disorders curable by allogeneic transplantation; however, significant toxicity with current regimens persists including severe graft-versus-host-disease (GVHD) leading to significant morbidity and mortality.
Moreover, mixed chimerism has been shown to be sufficient to induce clinical remissions in children with nonmalignant hematologic disorders undergoing conventional allogeneic transplantation. Therefore, newer regimens need to be developed that are more applicable to patients with non-malignant disorders in whom no graft vs. leukemia effect is needed, and where mixed chimerism is sufficient for disease amelioration.
In this protocol, we propose transplantation in patients with severe beta-globin disorders including sickle cell disease (SCD), and beta-thalassemia, considered at high risk for complications from or ineligible for standard BMT, with allogeneic PBSCs from an HLA identical sibling using a novel immunosuppressive regimen without myeloablation in an attempt to further decrease the transplant related morbidity/mortality.
The low intensity nonmyeloablative conditioning regimen will consist of low dose radiation, Alemtuzumab (Campath ) and Sirolimus (Rapamune ) as a strategy to provide adequate immunosuppression to allow sufficient engraftment for clinical remission with a lower risk of GVHD development. T-cell replete, donor-derived, granulocyte colony stimulating factor (filgrastim, G-CSF) mobilized PBSCs will be used to establish hematopoietic and lymphoid reconstitution.
The primary endpoint of this study is treatment success at one year, defined as full donor type hemoglobin on hemoglobin electrophoresis for patients with SCD and transfusion-independence for patients with beta-thalassemia. Other end points include degree of donor-host chimerism necessary for long-term graft survival and disease amelioration, incidence of acute and chronic graft-vs-host disease (GVHD), incidence of graft rejection, transplant related morbidity, as well as disease-free and overall survival.