Conditioning Regimen for Allogeneic Hematopoietic Stem Cell Transplantation of Patients With Hematological Diseases

Participants in this study have a hematologic malignancy (a disorder in the bone marrow that affects the body's ability to create blood) that might benefit from receiving an allogeneic stem cell transplant (meaning the cells come from a donor) from a family member or nearly identical matched donor. The donor may either be a matched sibling, a mismatched family member, or an unrelated person. Usually these patients are given high doses of chemotherapy before receiving a stem cell transplant to keep their immune system from rejecting the donor stem cells and to kill any diseased cells that remain in the body. However, this group of patients have a high risk of developing possibly life-threatening treatment-related side effects such as infections, damage to vital organs such as lungs, liver, kidney and heart, as well as graft versus host disease (GVHD). Instead of the high dose chemotherapy and radiotherapy usually given before a transplant, this research study uses a new pre-transplant combination of three drugs, Fludarabine, Anti-CD45 and CAMPATH-1H with low dose radiotherapy. Fludarabine is a chemotherapy drug while Anti-CD45 and CAMPATH-1H are antibodies against certain types of blood cells, including those which are causing this disease. CAMPATH-1H is particularly important because it stays active in the body for a long time after it is given, which means it may work longer to prevent GVHD symptoms. Anti-CD45 may help in eradicating residual malignant cells. All these agents also help in preventing rejection of donor stem cells. This study is designed to give a less intense chemotherapy and radiotherapy, so that the life-threatening toxicities of conventional high dose chemotherapy and radiotherapy regimen can be reduced, while maintaining the ability to cure cancer.