As evidence of immune system involvement in the development of MS has grown, trials of various new treatments to alter or suppress immune response are being conducted. Most of these therapies are, at this time, still considered experimental.
Results of recent clinical trials have shown that immunosuppressive agents and techniques can positively (if temporarily) affect the course of MS; however, toxic side effects often preclude their widespread use. In addition, generalized immunosuppression leaves the patient open to a variety of viral, bacterial, and fungal infections.
Over the years, MS investigators have studied a number of immunosuppressant treatments. One such treatment, Novantrone (mitoxantrone), was approved by the FDA for the treatment of advanced or chronic MS. Other therapies being studied are cyclosporine (Sandimmune), cyclophosphamide (Cytoxan), methotrexate, azathioprine (Imuran), and total lymphoid irradiation (a process whereby the MS patient's lymph nodes are irradiated with x-rays in small doses over a few weeks to destroy lymphoid tissue, which is actively involved in tissue destruction in autoimmune diseases). Inconclusive and/or contradictory results of these trials, combined with the therapies' potentially dangerous side effects, dictate that further research is necessary to determine what, if any, role they should play in the management of MS. Studies are also being conducted with the immune system modulating drug cladribine (Leustatin).
Another potential treatment for MS is monoclonal antibodies, which are identical, laboratory-produced antibodies that are highly specific for a single antigen. They are injected into the patient in the hope that they will alter the patient's immune response. One monoclonal antibody, natalizumab (Tysabri), was shown in clinical trials to significantly reduce the frequency of attacks in people with relapsing forms of MS and was approved for marketing by the U.S. Food and Drug Administration (FDA) in 2004. However, in 2005 the drug's manufacturer voluntarily suspended marketing of the drug after several reports of significant adverse events. In 2006, the FDA again approved sale of the drug for MS but under strict treatment guidelines involving infusion centers where patients can be monitored by specially trained physicians.
Another experimental treatment for MS is plasma exchange, or plasmapheresis. Plasmapheresis is a procedure in which blood is removed from the patient and the blood plasma is separated from other blood substances that may contain antibodies and other immunologically active products. These other blood substances are discarded and the plasma is then transfused back into the patient. Because its worth as a treatment for MS has not yet been proven, this experimental treatment remains at the stage of clinical testing.
Bone marrow transplantation (a procedure in which bone marrow from a healthy donor is infused into patients who have undergone drug or radiation therapy to suppress their immune system so they will not reject the donated marrow) and injections of venom from honey bees are also being studied. Each of these therapies carries the risk of potentially severe side effects.