Stem Cell Transplantation and T-Cell Add-Back to Treat Bone Marrow Malignancies

Bone marrow stem cell transplant studies carried out by the National Heart Lung \& Blood Institute (NHLBI) Bone Marrow Transplantation (BMT) Unit have focused on approaches to optimize the stem cell and lymphocyte dose in order to improve transplant survival and increase the graft-versus-leukemia effect. The aim is to create the transplant conditions that permit rapid donor immune recovery without causing graft-versus-host disease (GVHD) by using reduced post-transplant immunosuppression in conjunction with a transplant depleted of T cells to a fixed low dose, below the threshold known to be associated with GVHD. We have found that the outcome from transplant is improved by controlling the stem cell (CD34+ cell) and T lymphocyte (CD3+ cell) dose. We use the "Nexell Isolex 300i" system to obtain high CD34+ doses depleted of lymphocytes to a fixed CD3+ T cell dose of 2 x 104/kg. The use of the cell separator and the monoclonal antibodies is covered by an Investigational Device Exemption. A persisting problem with these T cell depleted transplants has been the slow acquisition of full donor T cell engraftment (T cell chimerism). Two previous protocols have failed to increase the speed of donor T cell chimerism. Patients with mixed donor-recipient T cell populations are known to be at higher risk for late graft rejection and leukemic relapse after transplant. Therefore, the achievement of full donor chimerism remains an important therapeutic goal. In this study we will test whether cyclosporine given between day -6 and +21 after transplant can significantly improve day 30 T cell chimerism (the principle end-point). The study also will measure the incidence of acute and chronic GVHD, day 100 transplant related mortality, cytomegalovirus reactivation, relapse, and disease-free survival with appropriate safety stopping rules. This protocol follows closely previous studies in this series. Three additional modifications will be made however: 1) The first T cell add-back will be delayed until day 60 (instead of day 45) so as to continue to allow a 45 day period without cyclosporine immunosuppression. 2) No day 100 T cell add-back will be given. (In previous studies many patients have, for protocol-defined reasons, not received the second transfusion and there is no evidence that it is required). 3) Patients with high-risk leukemias with a high relapse probability will receive an additional chemotherapy agent prior to transplant using etoposide (VP16) 60mg/kg to improve the chance of remaining in remission.