Rituximab reduces disease activity in multiple sclerosis

May 2 2007

A new drug under investigation shows a reduction in disease activity in multiple sclerosis (MS), according to two studies that will be presented at the American Academy of Neurology's 59th Annual Meeting in Boston. The drug reduced disease activity as indicated by MRI scans.

Both of the studies involved people with the relapsing-remitting form of MS, where symptoms flare up and then subside. By 24 weeks, treatment with the drug rituximab reduced the number of areas of brain damage, or lesions, in people with MS and the number of relapses, or times when symptoms flare up, when compared with placebo.

Rituximab is a therapeutic antibody that selectively targets and depletes a subset of immune cells called B-cells by targeting a specific protein on their surface.

"This is the first drug to target B-cells and may represent a potential new treatment strategy for relapsing-remitting MS," said study author Stephen Hauser, MD, of the University of California, San Francisco, and a member of the American Academy of Neurology. "While these are early stage clinical trials, these results are exciting, because the current drugs available for MS are only partially effective in reducing disease activity and preventing exacerbations. New and more effective treatments for MS are sorely needed, especially for people who do not adequately respond to currently available medications. These data are also important because they demonstrate that B-cells, which are the precursors of antibody-producing cells, play an essential role in mediating relapses of MS."

In the first study, a randomized, placebo-controlled trial, 69 people were given two infusions of rituximab two weeks apart and 35 were given a placebo. The participants were followed for six months. Those given rituximab had approximately 90 percent fewer brain lesions than those given placebo. During the six-month period, 58 percent fewer of those taking the drug had relapses than those taking placebo; 14.5 percent of the rituximab patients experienced at least one relapse during the six-month period, compared to 34.3 percent of the patients receiving a placebo.

"Treatment with rituximab was generally safe and well-tolerated in the study," Hauser said. With the exception of infusion-associated adverse events, the rates of adverse events and serious adverse events were comparable between those taking rituximab and those taking placebo. Although there were more first infusion-associated adverse events with rituximab, the majority of adverse events resolved with appropriate medical treatment. The overall rates of infection were also comparable with rituximab and placebo.

In the second study, an uncontrolled open label trial, 26 people received two infusions of rituximab two weeks apart (one course of treatment) and then another treatment course six months later. Patients were followed for a total of at least one year. Though a placebo group was not included in this safety study, brain lesions were reduced by more than 90 percent and the relapse rate was reduced from an average of at least one per patient per year to only a few for the entire group over the year of treatment. Side effects were limited to mild to moderate reactions to the drug infusion, according to study author Amit Bar-Or, MD, of the Montreal Neurological Institute at McGill University in Montreal, Canada, and a member of the American Academy of Neurology.

Both studies were supported by Genentech, Inc., and Biogen Idec., the companies marketing the drug in the United States. The drug is currently approved for use with certain types of lymphoma and for a moderate to severe form of rheumatoid arthritis; it is not approved for use in multiple sclerosis.

Rituximab has been associated with fatal infusion reactions, tumor lysis syndrome, progressive multifocal leukoencephalopathy, renal toxicity, and other adverse effects.