Future research directions in multiple sclerosis therapies.

The success of presently available injectable immunomodulatory therapies in treating multiple sclerosis has led to heightened interest in finding even more efficacious and better tolerated therapies. Several oral agents have shown efficacy in phase-II clinical trials and are now entering phase-III pivotal trials. In addition, monoclonal antibodies targeting surface receptors on various cells of the peripheral immune system have also shown efficacy in early studies and will soon be entering phase III. All of these approaches target immune molecules that are not specific for multiple sclerosis (MS) and carry inherent risk of infection and systemic side effects. Novel immunotherapies in preclinical or phases I to IIa testing are attempting to more selectively target pathogenic effector cells and thereby block abnormal immune cell activation without compromising normal healthy immune responses. The induction of tolerance to self-proteins continues to be a goal of MS immunotherapy, but as yet has not been accomplished outside of the laboratory. There is increasing awareness of the need to understand and modulate nonclassical immune targets as well as central nervous system degenerative processes. The roles of vitamins, antimicrobials, and hormones continue to be studied. The mechanisms of neurodegeneration in MS are likely multifactorial and include direct damage by T cells and humoral immunity as well as oxidative stress, glutamate-mediated excitotoxicity, and neuronal and oligodendrocyte apoptosis. Neuroprotective drugs that were once only considered for classical degenerative diseases, such as amyotrophic lateral sclerosis and Parkinson's disease, are now being considered in MS.