Researchers continually search for new or better medications to treat multiple sclerosis (MS). Since MS appears to be a disease in which the immune system attacks the covering of the nerves (myelin) within the brain and spinal cord, treatments that reduce the activity of the immune system may slow the progression of the disease. Medications that work in this manner are called immunosuppressants. They are a major focus of MS research.

Several immunosuppressants are being studied or used for MS:¹

• Cyclophosphamide (Cytoxan), which many experts believe stabilizes MS without improving it. But research has shown conflicting results.
• Cladribine (Leustatin or CdA), which has been used successfully against leukemia. Again, research has shown conflicting results.
• Methotrexate (Rheumatrex), which has also been used to treat cancer and rheumatoid arthritis. This drug may be of limited benefit in reducing the progression of MS.

Any therapy that can be used to treat MS must be judged by how it affects a person's degree of disability. Newer studies rely on the results of MRI scans and the progression of disability to evaluate how well therapy is working.