BOSTON (Reuters) - Two infusions of the cancer drug Rituxan given 2 weeks apart slowed the progression of multiple sclerosis for nearly 1 year, researchers reported on Wednesday.
And Rituxan appears to be twice as effective as first-line treatments for MS, which reduce the number of relapses by about one third, the researchers said.
“It’s quite remarkable that the effect was sustained for 48 weeks with just a single course of therapy,” said Dr. Stephen Hauser of the University of California at San Francisco, who worked on the study published in The New England Journal of Medicine.
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.
Although no head-to-head comparison has been done, Hauser said Rituxan appears to work better than existing therapies.
His team tested patients with the relapsing-remitting form of the disease, in which symptoms wax and wane over many years, making it difficult to gauge whether a treatment is really working. They make up about half the patients with MS.
To assess the progress of the Rituxan treatments, they used magnetic resonance imaging, or MRI, scans to see damage to the nervous system.
“What was so surprising here is that the effect on MS inflammatory measures was so fast,” Hauser said. The number of lesions they could see dropped immediately after the two treatments.
Within 12 weeks, there were almost no old or new lesions, while the number of lesions on volunteers who received placebo shots tended to stay the same or increase in number.
But the drug was not as good at preventing relapses.
After 48 weeks, 20 percent of the 69 Rituxan recipients had suffered a relapse. That was still much better than the 35 patients who got placebo infusions and had a relapse rate of 40 percent.
Rituxan, known generically as rituximab, is made by the biotechnology companies Genentech Inc. and Biogen Idec Inc., which sponsored the study.
It is approved for non-Hodgkin’s lymphoma and rheumatoid arthritis and sold by Roche AG as MabThera outside the United States, Japan and Canada.
Hauser expressed concern that, based on the new results, doctors may begin using the drug on their MS patients even though it has not been approved for that use.
“This trial was not designed to assess long-term safety or to detect uncommon adverse events,” the researchers wrote.
“It would be a tragedy if the drug were to get dinged because of a side effect in a patient that shouldn’t have received the drug,” he said.
The research has also given doctors a better idea of what causes MS, according to Hauser. Rituxan is a monoclonal antibody, a genetically engineered immune system protein, that attacks immune cells called B cells.
“This study has taught us that B cells are absolutely essential to the genesis of inflammatory attacks in multiple sclerosis,” Hauser said.