FDA Will Determine Whether Risks Outweigh Any Potential Benefit
Serious side effects associated with Tysabri may outweigh any potential benefit, according to a study published in early November 2005, such that the once-promising drug for multiple sclerosis (MS) and Crohn's disease will not likely return to the U.S. market.
In the November 3, 2005 issue of the New England Journal of Medicine ("NEJM") appears an article about a new concerning Tysabri (natalizumab). This Tysabri study was comprised of two trials, and was supported by the drug companies responsible for Tysabri -- Elan Corp. and Biogen Idec Inc. -- as well as the National Institutes of Health. The November 2005 NEJM article found that there was some positive response for MS patients and Crohn's patients using Tysabri. The NEJM Tysabri study article, however, pointed out once again that one Crohn's patient died from progressive multifocal leukoencephalopathy (PML), a rare but potentially fatal brain infection.
This is not the first time PML has been related to Tysabri, which has a short but controversial track record. Tysabri was approved by the FDA in November 2004 for the treatment of multiple sclerosis (MS) and Crohn's disease. Soon thereafter, in February 200 Tysabri was voluntarily removed from the market by Elan Corp. and Biogen Idec Inc. after reports surfaced that three patients taking Tysabri had developed PML. Two of three (or four, according to some reports) Tysabri patients who developed PML, an opportunistic infection, died as a result.
Dr. John F. Thompson, a professor of pediatrics and director of the Division of Pediatric Gastroenterology and Nutrition at the University of Miami's Miller School of Medicine, gave his opinion about this latest Tysabri study to HealthDay reporter Amanda Gardner:
Response rates weren't overwhelming but they were certainly exciting, particularly for people who had failed other therapies. It probably would have become another important medication to consider for people with problematic Crohn's disease but the opportunistic infection is going to be problematic. I certainly would be uncomfortable using it in my patients.
Dr. Thompson concluded it did not seem likely that Tysabri would go back on the U.S. market, given the results of the latest Tysabri study. Ms. Gardner points out that Dr. Thompson was not involved with the latest Tysabri study.
According to Ms. Gardner's HealthDay article, published on November 2, 2005, Tysabri maker Elan was more optimistic. Davia Temin, an Elan spokeswoman, said:
Both [Elan and Biogen Idec] are extremely positive about its prospects for coming back onto the market. Obviously, we want to come up with an appropriate risk analysis and patient safety comes first, but there is a huge unmet patient need.... There has been a very stringent and comprehensive risk analysis safety evaluation that's been done and that has been extremely favorable. For PML, there were no new cases found in any population. It's the exact same three people.
According to Elan's Temin, the FDA is currently reviewing safety data on Tysabri and the agency should be done with its Tysabri review in about six months.
(Posted by: Tom Lamb)