May 1, 2007 (Boston) -- A drug that is already used to treat cancer and rheumatoid arthritis cut by more than half the chance that people with multiple sclerosis would have their symptoms flare up over a six-month period, researchers report.
"We believe that if we can prevent these lesions, we can modify the course of this disease," says researcher Stephen Hauser, MD, chairman of neurology at the University of California, San Francisco, and president of the American Neurological Association.
If the research pans out, "this would be a very attractive and probably blockbuster therapy," he tells WebMD.
The research was presented at the American Academy of Neurology's 59th Annual Meeting.
How Rituxan Works
The exact cause of multiple sclerosis (MS) is unknown. But the disease is thought to be triggered by a malfunction in the immune system that prompts immune cells to attack the brain and/or spinal cord. The most common form of multiple sclerosis is a relapsing-remitting form in which relapses or "attacks" of worsening neurologic function appear, and then disappear, for months or years at a time.
Like many other drugs for MS, Rituxan targets the immune system to help calm the inflammation that scars nerves, leading to disease progression. But Rituxan homes in on the immune system in a brand new way, Hauser says.
The drug works by targeting cells in the immune system called B cells, which make antibodies that contribute to the disease process. B cells also secrete chemicals that can encourage inflammation, he says.
Also, it's more convenient, requiring only two infusions every six months or so instead of the daily to weekly injections associated with current therapies, Hauser says.
Fewer Flare-ups in People on Rituxan
Both of the new studies involved people with the relapsing-remitting form of MS. In the first study, 69 people were given two one-hour infusions of Rituxan two weeks apart and 35 were given a placebo.
Over the next six months, 58% fewer people taking the drug had their symptoms flare up than those taking placebo: 14.5% of those on Rituxan experienced at least one relapse compared with 34.3% of those receiving a placebo.
Also, those on Rituxan had 91% fewer brain lesions seen on MRIs than those on placebo, Hauser says.
The second study, designed to look at the safety of the drug, showed "no unexpected problems," says researcher Amit Bar-Or, MD, of the Montreal Neurological Institute at McGill University in Montreal.
Twenty-six of 28 people were able to complete the 48-week study, in which they received two infusions of Rituxan two weeks apart and then another course six months later.
Safety a Concern
Gary Birnbaum, MD, director of the Multiple Sclerosis Treatment and Research Center in Golden Valley, Minn., says a big worry is a rare but rapidly fatal viral infection known as progressive multifocal leukoencephalopathy, or PML.
And while people on Rituxan appear to have fewer MS flare-ups, "we still don't know if it will actually stop disease progression," Birnbaum tells WebMD.
"These are important observations," Birnbaum says. "But we need longer trials to assess safety and effectiveness."
Immediate Drug Therapy Better Than Waiting
In a third study presented at the meeting, researchers reported that people who immediately start taking Betaseronat the first signs of MS are 41% less likely to have another attack over the next three years than those who delay treatment until they are diagnosed, as is currently done.
Betaseron is a brand of the interferon beta medications that are already used to treat people with relapsing-remitting MS. Other brands of interferon beta, which may reduce the frequency of relapses and delay disability, are Avonex and Rebif.
"I was one of those skeptics who told patients [who had one attack] we could wait," says researcher Mark S. Freedman, MD, director of the Multiple Sclerosis Unit at the University of Ottawa.
"But it turns out there is an 80% chance a person who has one attack will meet the criteria for MS by two years," he tells WebMD. "Immediate treatment can prevent or delay the chance of progression."
Freedman says it's possible that immediate treatment with the other interferon beta medications would provide the same benefit. "But it hasn't been shown."