FRIDAY, June 14, 2002 (HealthDayNews) -- Although researchers are busily working to find therapies for multiple sclerosis (MS), a devastating disease affecting the central nervous system, so far only one drug has been approved specifically to treat the progressive form of the disease.
And even though the drug won U.S. Food and Drug Administration approval more than a year and a half ago, many feel it is underused.
Mitoxantrone, which goes by the brand name Novantrone, was originally developed to treat cancer, but was found to have a beneficial effect on severely ill MS patients as well.
"Mitoxantrone is something we needed," says Dr. Saud Sadiq, chairman of the department of neurology and director of the MS Research and Treatment Center at St. Luke's Roosevelt Hospital Center in New York City. "It's an important addition to stopping the disease in severely affected patients."
Other drugs, including the chemotherapeutic agent cytoxan, are used to treat this form of MS, which worsens over time, but they are not specifically approved for the disease.
The problem is that mitoxantrone is "potentially a very toxic drug," says Stephen Reingold, vice president of research programs at the National Multiple Sclerosis Society. "There are no particular guidelines as to how it should be used, especially in the context of other medications, and the medical community is trying to sort that out."
Physicians' main concern is that, after a certain threshold, the drug can cause potentially life-threatening heart problems. It's difficult to reach this threshold because the drug is given intravenously, with supervision, but it has happened.
"The problem of cardiac toxicity has been recognized for a long period of time and it's not a minor issue, but I think it's been stated repeatedly that there is no evidence of cardiotoxicity with mitoxantrone in the recommended doses," says Dr. William Sheremata, professor of neurology and director of the MS Center at the University of Miami School of Medicine.
Sadiq presented a paper examining some of the lesser side effects of mitoxantrone at the Consortium of MS Centers meeting in Chicago this month. He reported few adverse effects, but he did not go up to doses necessary to induce cardiac toxicity. "We want physicians to be more comfortable about using the drug," Sadiq says.
Though no one is sure exactly why mitoxantrone is effective, the drug appears to work by suppressing the immune system. The vast majority of MS patients have abnormal immune systems, Sadiq says. Damage to the nerve fibers, which is the hallmark of the disease, is believed to be caused by an autoimmune response or the result of the immune system reacting against itself.
Much current research is looking at ways to modulate the immune system. Some investigators believe the immune system of MS patients has been compromised by an as-yet unrecognized chronic viral or bacterial infection, and they are looking at long-term antibiotic treatment. "That's always been a nagging thing at the back of physicians' minds," Sadiq says.
There's also apparent potential in trying to repair nerve fibers, either with growth factors or with stem cells. Human trials involving stem cells probably won't start for another five years or so, Sadiq predicts.
Researchers are also looking at the possibility of stopping immune cells from crossing the blood-brain barrier, something that happens in most people with MS. Early trials with a drug called Antegren showed an 85 percent reduction in relapses, says Sheremata, who is involved with the trials.
"We're very excited about this. One injection prevented any cells from getting across for four months," he says. "There is a bright light down at the end of the tunnel."
What To Do
For more information on mitoxantrone, visit the National Library of Medicine. For more information on multiple sclerosis, visit the National Multiple Sclerosis Society.
