Non-Myeloablative HLA-Matched Ex-Vivo T-cell Depleted Stem Cell Transplantation for Hematologic Malignancies

The purpose of this trial is to determine if patients with hematologic diseases who have a HLA 6/6 matched related donor and are not eligible for a standard myeloablative stem cell transplant will have less severe graft versus host disease (GVHD), transplant related mortality, and less graft failure when treated with a non-myeloablative T-cell depleted stem cell transplant.

Our prior experience in the lab and in clinical trials with non-myeloablative HLA-matched and mismatched transplant strategies have been remarkable for a low transplant related mortality rate, but a still formidable risk of GVHD and graft rejection. In this trial, we have incorporated a combination ex-vivo T-cell depletion strategy to prevent GVHD with vigorous in vivo depletion of host (and to a lesser extent donor) T-cells to prevent graft rejection. Patients will receive non-myeloablative conditioning with cyclophosphamide, thymoglobulin, fludarabine, and thymic irradiation, followed by a T-cell depleted PBSC infusion. Cyclosporine will be given for GVHD prophylaxis, and tapered beginning on day 35. Data from our mouse model and previous clinical trials have demonstrated that this approach can induce mixed chimerism without GVHD, with the potential for conversion of mixed chimerism to full donor hematopoiesis following donor leukocyte infusions.