The unanimous vote by advisers to the Food and Drug Administration came amid regulators' own concerns about the drug Tysabri, and whether there is any way to minimize risk from the apparently rare side effect.
But the advisers were debating some controls on who could use the drug, agreeing to a manufacturer proposal for a mandatory patient registry. They were scheduled to decide later in the day who would be allowed to enroll in the registry, and how tightly drug use would be limited.
Tysabri has been linked to a potentially fatal brain infection called progressive multifocal leukoencephalopathy, or PML. The drug's manufacturers voluntarily pulled it from the market last year, following the deaths of two patients. The drug had been sold for just four months.
Now Biogen Idec Inc. and Elan Corp. PLC want to bring back Tysabri under a still-evolving risk-management plan that would control and limit use of the once-a-month intravenous drug to patients with relapsing MS.
The FDA isn't required to follow its advisers' recommendations, but usually does. If it goes along this time, Tysabri would become only the second prescription drug ever returned to the market after being pulled because of dangerous side effects, following the revival of Lotronex, used to treat irritable bowel syndrome.
Dozens of tearful multiple sclerosis patients pleaded with FDA's advisory committee Tuesday to allow them to choose for themselves whether to take Tysabri.
"I am at the end of my road, in terms of what I can take. I want it to be my choice," said Barbara Crooks, 48, shortly before testifying. She and her husband, David, traveled from the Pittsburgh area to speak.
Biogen Idec and Elan withdrew Tysabri from the market in February 2005 after two patients in clinical trials involving 7,000 people died of PML. Should sales resume, even more patients, perhaps one in every 1,000, eventually will get the often-fatal virus believed to cause PML, said Dr. Russell Katz, director of the FDA's Division of Neurology Products.
FDA staff have recommended patients be monitored during treatment and for at least five years thereafter to minimize the risk of infection associated with Tysabri, also known as natalizumab.
Three studies recently published by the New England Journal of Medicine found that Tysabri alone or with standard interferon treatment cut the rate of relapse in MS patients by as much as two-thirds after two years and reduced the number of people whose MS got worse, compared to those on a dummy treatment or interferon alone.
"The two-thirds reduction in relapse rate cannot be ignored. It is a striking result," said Dr. Richard Rudick, a neurologist at the Cleveland Clinic who appeared before the panel on behalf of Biogen.
Trading of shares in both Biogen Idec and Elan have been halted for the duration of the two days of FDA meetings.