Phase II Trial of a Chemotherapy Alone Regimen of IV Busulfan (Busulfex), Melphalan and Fludarabine as Myeloablative Regimen Followed by an Allogeneic T-Cell Depleted Hematopoietic Stem Cell Transplant From an HLA-Identical, or HLA-Non Identical Related or Unrelated Donor

The trial proposed is a single arm, phase II treatment protocol designed to examine the engraftment, toxicity, graft-versus-host disease and ultimate disease-free survival following transplants derived from (1) HLA-matched siblings or related donors, (2) HLA-compatible unrelated donors or (3) HLA haplo-type mismatched related donors using a new chemotherapeutic cytoreductive regimen. Candidates for transplant will be stratified according to their donor types. Candidates for this trial will include patients with high risk forms of ALL, AML or CML, non-Hodgkin's lymphoma, or myelodysplastic syndrome for whom an allogeneic marrow transplant is clearly indicated, and patients with aplastic anemia refractory to ATG or cyclosporine treatment and who are transfusion dependent. All research participants will be conditioned for transplantation with intravenous busulfan (busulfex®) (0.8- 1.0 mg/Kg/dose Q6H x 10 doses), melphalan (70 mg/m2/dose x 2 doses) and fludarabine (25mg/m2/day x 5 doses). Doses of busulfan will be adjusted according to plasma levels. All research participants will also receive ATG (Thymoglobulin®) prior to transplant to promote engraftment. No drug prophylaxis againstGvHD will be administered post transplant. All research participants will also receive G-CSF post-transplant to foster engraftment. The preferred source of stem cells will be peripheral blood stem cells (PBSC) induced and mobilized by treatment of the donor with G-CSF for 5-6 days. PBSC obtained through 2-3 leukaphereses will be Isolex® 300i separated CD34+ stem cell column selected and E-rosette depleted (E-). The CD34 + E peripheral blood progenitors will then be administered to the research participants after they have completed cytoreduction. If the use of CD34 + E- PBSC is not possible, the alternative graft will consist of bone marrow derived stem cells T-cell depleted by soybean agglutinin and E-rosetting (SBA-E-). Research participants will be carefully monitored for engraftment, chimerism, incidence and severity of acute and chronic GvHD, regimen-related toxicity, characteristics of hematopoietic and immune reconstitution and ultimate survival and disease-free survival. This phase II trial is designed to investigate the feasibility and safety of a chemotherapy-based cytoreductive regimen plus a T-cell depleted peripheral blood stem cell (PBSC) or bone marrow stem cell transplant (BMT) for the treatment of high risk patients with advanced stages of hematologic malignancies. The majority of research participants will receive grafts derived from PBSC and will be the focus of the trial. The study population will be segmented into three research participant groups based on the type of donors used for the hematopoietic stem cell graft: (1) HLA-identical sibling or related donor, (2) HLA-compatible unrelated donor, and (3) HLA-mismatched related donor. A maximum of 25 PBSC research participants in both related groups will be accrued onto the study; a maximum of 70 PBSC research participants in the unrelated group will be accrued. In order to reduce patient risk, the study design includes early termination of any trial group in the event of excessive graft failure, grade 3-4 acute graft-versus-host disease, or early transplant related mortality during the accrual period. Excessive failure is defined differently in the three donor groups. Stopping rules for the three research participant populations will be utilized. In addition to the 120 PBSC research participants, we anticipate approximately 25 BMT research participants treated across the three donor groups. These research participants will be followed and at the conclusion of the trial descriptive statistics on this subgroup will be recorded.