The novel cancer and rheumatoid arthritis drug Rituxan has proven to be effective when administered to patients who are diagnosed with multiple sclerosis (MS).

The study, supported by Biogen Idec. and Genentech, the drug’s manufacturers, followed 104 patients for 48 weeks.  The researchers discovered that 20 percent of those who received Rituxan relapsed compared with 40 percent of those who received placebo.

“The findings shift the perspective on the cause of MS and open a new frontier for investigation,” Stephen Hauser, UCSF’s neurology chairman and the study’s lead author told the San Francisco Chronicle.

Rituxan, known generically as rituximab, targets immune system cells called B-cells. Studies by the UCSF researchers and others suggest that B cells and related pathways play a key role in destroying myelin.

If the findings are confirmed in larger, phase III studies, the Rituxan research opens a new frontier for the study of the cause and treatment of MS, Hauser said.

"No matter what happens with Rituxan down the road, this represents a paradigm shift that has profound implications for our understanding of MS," Hauser said.

Multiple sclerosis, which affects as many as 350,000 people in the United States and 2 million worldwide, is apparently caused when the immune system attacks and breaks down the insulation surrounding cells that make up the brain and spinal cord. 

MS symptoms may include blurred vision, loss of balance, poor coordination, extreme fatigue, paralysis and blindness. There is no cure.

Rituxan was approved in 1997 for patients with non- Hodgkin's lymphoma, and for rheumatoid arthritis in 2006.

Rituxan had $2.29 billion in U.S. sales in 2007. Genentech, based in South San Francisco, California, rose 95 cents, or 1.3 percent, to $71.80 at 5:21 p.m.

The study is published in the February 14 issue of The New England Journal of Medicine.