MS is a chronic autoimmune disease of the central nervous system in which myelin, the protective coat that surrounds nerve cells, is damaged or destroyed by autoimmune T cells and macrophages, leading to an eventual loss of neurologic function. In a pilot study in Europe using high-dose chemotherapy, it was observed that 18 of 19 MS patients stabilized or improved clinically, and only one patient showed a new lesion on magnetic resonance imaging (MRI) of the brain at 4.5 years after treatment. Improvement was seen in quality-of-life assessments.

In ITN033AI, high-dose chemotherapy with autologous CD34-selected hematopoietic cell transplantation will be given to confirm the results from the pilot study and to offer therapy to patients with early MS and a poor prognosis. Research studies will be performed in addition to clinical assessments to better understand the effect of the treatment on the activity of MS. High-dose chemotherapy will be used to deplete autoreactive immune cells. These regimens also deplete the bone marrow, the source of blood-forming CD34+ stem cells which causes very low blood counts. Therefore, the participant's autologous CD34+ hematopoietic stem cells will be collected before high dose immunosuppressive therapy is given and then returned as a transplant post-chemotherapy. Patients will be followed closely after the autologous transplantation since they will be at risk for infections after treatment.

At the beginning of the study, participants will undergo a number of screening and baseline procedures, including a physical exam, blood collection, MS-confirming neurology exams and questionnaires, and MRI procedures. Participants will be given prednisone and granulocyte-colony stimulating factor (G-CSF) to mobilize CD34+ hematopoietic stem cells from the bone marrow into the peripheral blood. When the peripheral blood CD34+ cell count reaches 20,000 cells/ml or greater, these cells will be collected by leukapheresis. In this process, a catheter is placed into a large blood vessel, peripheral blood is withdrawn, and a high speed sedimentation (leukapheresis) device is used to separate and retain the cells required for autologous transplantation. Other blood cells are then returned to the participant's body. In the laboratory, the CD34+ hematopoietic stem cell graft will be selected and prepared from the leukapheresis collection, and stored until needed for transplant. Seven or more days following the collection of their autologous graft, participants will be hospitalized and receive high-dose chemotherapy consisting of carmustine, etoposide, cytarabine, and melphalan (BEAM) and thymoglobulin. This is followed by transplantation of the autologous hematopoietic cell graft. Participants will remain in the hospital for observation during recovery of their peripheral blood cell counts, as described in the protocol. Participants will receive G-CSF and blood transfusions, if needed, and will be monitored for infections. Following discharge from the hospital, eight study visits will occur over sixty months (five years). During these visits, participants will undergo blood and urine collection, MRI studies, leukapheresis, and MS neurology exams and will complete questionnaires.