Donor Stem Cell Transplant With Treosulfan, Fludarabine, and Thiotepa in Treating Patients With Non-malignant Disorders

This phase II clinical trial studies how well treosulfan, thiotepa, fludarabine, and rabbit anti-thymocyte globulin (rATG) before donor stem cell transplantation works in treating patients with nonmalignant (non-cancerous) diseases. Hematopoietic cell transplantation has been shown to be curative for many patients with nonmalignant (non-cancerous) diseases such as primary immunodeficiency disorders, immune dysregulatory disorders, hemophagocytic lymphohistiocytosis, bone marrow failure syndromes, and hemoglobinopathies. Powerful chemotherapy drugs are often used to condition the patient before infusion of the new healthy donor cells. The purpose of the conditioning therapy is to destroy the patient's abnormal bone marrow which doesn't work properly in order to make way for the new healthy donor cells which functions normally. Although effective in curing the patient's disease, many hematopoietic cell transplantation regimens use intensive chemotherapy which can be quite toxic, have significant side effects, and can potentially be life-threatening. Investigators are investigating whether a new conditioning regimen that uses less intensive drugs (treosulfan, thiotepa, and fludarabine phosphate) results in new blood-forming cells (engraftment) of the new donor cells without increased toxicities in patients with nonmalignant (non-cancerous) diseases.