Thymoglobulin to Prevent Acute Graft vs. Host Disease (GvHD) in Patients With Acute Lymphocytic Leukemia (ALL) or Acute Myelogenous Leukemia (AML) Receiving a Stem Cell Transplant

This study involves the use of a drug called Thymoglobulin, which is approved in the USA to treat kidney transplant rejection and in Canada to treat and to prevent kidney transplant rejection. Thymoglobulin is not approved for the treatment or prophylaxis of graft versus host disease in bone marrow transplantation. This study is to evaluate two (2) doses of Thymoglobulin and its safety and effectiveness when used with a "myeloablative" conditioning regimen prior to receiving a stem cell transplant (also called bone marrow transplantation) from a matched, related donor. A myeloablative regimen is typically composed of chemotherapy and radiation and destroys the subject's existing bone marrow. Subjects meeting all inclusion and exclusion criteria and who have a relative with matching (genetically similar) stem cells who are also willing to donate them (i.e. matched-related-donor) are eligible to participate in this study. Following myeloablative therapy, the donor's cells are then transplanted (i.e. infused) into the subject's blood stream. One of the most common complications of this type of transplant is graft-versus-host disease (GvHD). This is a condition where the transplanted donor cells attack the transplant recipient's body. Treatments, such as cyclosporine, are used to minimize the risk of GvHD following stem cell transplantation. To enter this study, subjects must be having a matched-related donor stem cell transplant. If a subject qualifies for entry into this study, he/she will be assigned to receive Thymoglobulin at a dose of 4.5 mg/kg or 8.5 mg/kg. The treatment assignment is random and is not chosen by the subject or their physician. Subjects are admitted to the hospital for the transplant procedure and are treated with Thymoglobulin over 3-5 days just prior to receiving the donor stem cells. The subject will also receive standard GvHD prophylaxis with cyclosporine. Methotrexate, which is commonly used by transplant centers to minimize the risk of