Feb. 14 (HealthDay News) -- A drug originally designed to combat cancer that is now being used to treat autoimmune diseases such as rheumatoid arthritis and lupus might also work against a common form of multiple sclerosis.

In new research published in the Feb. 14 issue of the New England Journal of Medicine, researchers reported that one treatment with rituximab significantly reduced the number of inflammatory lesions in the brains of people with relapsing-remitting multiple sclerosis (MS), and almost halved the incidence of relapse for up to 48 weeks.

"The immediate results of this study should give great hope to all of us in the field and to our patients," said study author Dr. Stephen Hauser, chairman of the department of neurology at the University of California, San Francisco. "An easily-administered, relatively safe IV therapy might have a very important, profound effect on the relapsing-remitting phase of MS."

However, Hauser was quick to caution, "these results are preliminary and should not be translated into a belief that a new proven therapy has been identified." He said that larger, longer studies need to be done to fully assess the drug's safety and efficacy in people with MS.

"We are cautiously optimistic," Dr. John Richert, executive vice president of research and clinical programs for the National Multiple Sclerosis Society, said of the findings. "It's hard to imagine results any better than this, but right now, we don't have any long-term data on safety or efficacy."

MS is an autoimmune disease that affects the central nervous system. Instead of targeting foreign invaders, such as bacteria, the body mistakenly attacks the protective covering of nerve cells called myelin.

Most research has focused on the T-cell side of the immune system, but other studies began to suggest that maybe T-cells weren't the major players in MS after all, and that perhaps B-cells might play a role. Rituximab, sold under the brand name Rituxan, targets and depletes a type of B-cell known as CD20+.

Hauser's study included 104 people with relapsing-remitting multiple sclerosis. Someone with this type of MS will have disease flare-ups but will also have periods of remission when they don't have symptoms.

The volunteers were randomly assigned to receive either 1,000 milligrams of intravenous rituximab or a placebo. Magnetic resonance imaging (MRI) was conducted at 12, 16, 20 and 24 weeks to assess the number of inflammatory lesions -- a hallmark of MS -- present in the brain.

The number of lesions was reduced in people taking rituximab, and they also had fewer new lesions than those taking a placebo, both during the study and six months later.

The rate of relapse was also significantly reduced for those on rituximab. At the end of the 48-week study period, 20.3 percent of those on rituximab had experienced a relapse versus 40 percent of those on placebo.

What both Hauser and Richert found most exciting was the speed at which rituximab worked and the duration of the benefit, which continued long after the treatment had been administered.

"Beneficial effects were seen by four weeks," said Richert. "Among the reasons why these data are so exciting is that the effects persist after 48 weeks after one course of rituximab."

People taking rituximab did experience more side effects, though most of them were minor. "The big question is whether removal of B-cells will impact the immune system later," said Hauser.

Both Hauser and Richert said this study has also provided new information about the MS disease process, and it will likely open up additional avenues of MS research.

SOURCES: Stephen Hauser, M.D., Robert A. Fishman distinguished professor of neurology, and chairman, department of neurology, University of California, San Francisco; John Richert, M.D., executive vice president, research and clinical programs, National Multiple Sclerosis Society, New York City; Feb. 14, 2008, New England Journal of Medicine