MS Drug's Suspension Called Setback for Patients
Yet other medicines remain on market to treat the disease, experts say
TUESDAY, March 1, 2005 (HealthDay News) -- The suspension Monday of a recently approved biologic therapy for multiple sclerosis delivered a blow -- though not a fatal one -- to doctors' ability to treat the disease, experts said.
"Tysabri was a promising new avenue of therapy. It is different in what it did," said Dr. Marshall Keilson, director of neurology at Maimonides Medical Center in New York City. Maimonides was one of the centers participating in clinical trials of the drug.
"It had a different presumed mechanism of action, so we felt that we could use this in combination with other drugs and help prevent the disease in more ways than one," he added.
"People had been very hopeful" about the drug, added Nicholas LaRocca, director of health-care delivery and policy research at the National Multiple Sclerosis Society in New York City. "It's discouraging that a drug that looked so promising is now in limbo."
On Monday, Biogen Idec Inc. and Elan Corp. suspended clinical trials and sales of Tysabri (natalizumab) after one patient died of a central nervous system disorder and another fell ill with the disorder, progressive multifocal leukoencephalopathy (PML).
The same day, the U.S. Food and Drug Administration issued a public health advisory informing patients and their doctors of the suspension. The FDA, in conjunction with the drug makers, is also working to assess the exact nature of any link between Tysabri and PML.
PML is a rare and often fatal neurologic disease with no known effective treatment.
Multiple sclerosis is a chronic, potentially debilitating disease that strikes the central nervous system, including the brain and spinal cord. Doctors suspect MS is probably an autoimmune disease, in which the immune system mistakenly attacks part of the body.
Despite the suspension of Tysabri, which was called Antegren in clinical trials, LaRocca said it was important to remember that "treatment for MS has not come to a screeching halt."
There are other drugs on the market that, while not cures, can help slow or stabilize the disease, he said.
Tysabri received accelerated approval from the FDA in November 2004 after trials showed that it reduced relapses of multiple sclerosis by 66 percent after one year of treatment. When combined with Avonex, another MS drug, Tysabri reduced exacerbations by 54 percent compared to Avonex alone.
"This [the suspension] really puts into perspective short-term trials," Keilson commented. "When it was approved, everyone said, 'Gee, isn't it amazing that it was approved so quickly?' The data was so impressive they [the FDA] felt the need to approve it quickly. Now we know why the FDA needs to be more circumspect."
And now, too, he added, "everybody's off the drug and we are in the process of calling all patients to let them know that there could be something else going on."
"Unfortunately, that something going on [PML] is something that we have no treatment for. These people already have MS," he said.
According to Biogen, some 5,000 people have taken Tysabri since it was approved late last year. That's in addition to 3,000 who were involved in trials.
Both the company and the FDA expressed optimism that the drug would be brought back as a treatment for MS. Biogen said it hoped to put the drug back on shelves later this year. And Dr. Steven Galson, acting director of the FDA's Center for Drug Evaluation and Research, said in a statement that his agency "continues to believe Tysabri offers great hope to MS patients," the Associated Press reported.
In addition to its application for MS, Elan and Biogen have hopes the drug will also be able to help people with Crohn's disease and with rheumatoid arthritis.
Tysabri is a monoclonal antibody, one of a new generation of drugs called biologic therapies. These drugs are engineered to target very specific mechanisms in the body, to stave off unwanted side effects. Tysabri seemed to work against MS by preventing the passage of certain immune factors across the blood-brain barrier, LaRocca explained.
Tsyabri's troubles don't necessarily damn the larger group of biologic treatments, experts said.
"The products are not exactly the same. They do a lot of different things," Keilson said. "We do need longer trials."
"We've seen in the last few years a tremendous surge in the utilization of biologics, and I don't think that's going to go away," Keilson added. "We just need to understand what happened" with Tysabri.
The drug suspension is the latest in a series of problems with already-approved drugs roiling the FDA. On Tuesday, the agency asked Congress for authority to require certain warning changes on drug labels, rather than having to negotiate such changes with drug manufacturers.
The federal government's public health advisory can be found at the FDA.