FDA: Risk builds up with Tysabri infusions

FDA sent out a new Tysabri warning Friday, one emphasizing that the risk of a rare brain infection increases as treatment continues. Biogen Idec, which markets the multiple sclerosis drug, said the FDA's warning--and revision of Tysabri's labeling--was not new. "Either it was included as part of our last label update or it was information that we are making available on a monthly basis," a spokeswoman told Reuters.

In any case, the FDA's statement points out that the overall risk of a Tysabri patient acquiring progressive multifocal leukoencephalopathy is still within the ratio that's been on the drug's label for a while. What's different is the addition of numbers for PML risk by the number of Tysabri infusions received by a patient, broken down for patients in the U.S. and outside the country.

In both locales, the risk more than doubles from the first infusion to the 24th, 0.7 per 1,000 to 1.9 per thousand outside the U.S., and 0.3 to 0.8 in the U.S. These stats include all 31 new cases through January 10, FDA says. Nevertheless, FDA maintains that Tysabri's benefits outweigh its risks. About 66,000 people have been treated with Tysabri since it came back onto the market in 2006.

- read the FDA statement
- get the FDA's update for healthcare professionals
- see the Reuters news
- check out the Boston Business Journal piece