Multiple sclerosis (MS) is a central nervous system disorder characterized by inflammation, loss of the insulating tissue (myelin) surrounding and protecting nerve axons, and multifocal scarring.1 Multiple sclerosis is a prototypic autoimmune disease likely mediated by pathogenic T and B lymphocytes. There has been substantial progress in the management of MS during the past decade, with 10 variably effective therapies now available and approved by the US Food and Drug Administration (FDA). These therapies suppress the early relapsing-remitting form of MS; however, the late neurodegenerative phase of the disease, progressive MS, remains largely untreatable.