FDA Doesn’t Appear Overly Alarmed by Recent Cases of Brain Disease Associated With Tysabri; Working with Biogen Idec and Elan to Update Labeling

Xconomy Boston — 

Biogen Idec and Elan got clobbered by investors a few weeks ago when they reported that two new patients developed PML, the often-fatal brain infection, after taking Tysabri. But in an announcement about the cases on its website, the FDA doesn’t seem overly alarmed about the risk associated with drug for multiple sclerosis and Crohn’s disease from the Cambridge, MA-based biotech company (NASDAQ: BIIB) and its Irish partner (NYSE: ELN).

The FDA noted on its Web site this week what we’ve reported previously: that two patients in Europe who took Tysabri as a single agent for more than a year have been confirmed to have PML. The agency points out that 39,000 patients around the world are taking Tysabri, and 12,000 have been on it for more than a year. No new cases have been seen in the U.S., where about 7,500 patients have been taking the drug for more than a year, under a close patient monitoring program.

“While the two patients who developed PML were on monotherapy (taking the drug by itself, without other medicines), the FDA still believes that Tysabri monotherapy may confer a lower risk of PML than when Tysabri is used together with other immunomodulatory medicines,” the FDA said.

Since MS is an autoimmune disease in which the immune system attacks the coating around nerves, several drugs like Biogen’s Avonex work by blunting the immune system, which can make patients vulnerable to infections. Two previous cases of PML identified in February 2005 were among patients who took a combination of Tysabri and Avonex. That was scary enough at the time to get the companies to pull the drug off the market. The drug, now Biogen’s fastest-growing product, was reinstated by the FDA in July 2006 as patients clamored for it, saying the benefit of reducing MS flares was worth the risk.

The FDA noted that it is working with the companies to update Tysabri’s prescribing information, and pass the word on to doctors and patients. The agency has previously estimated the risk of getting PML at about 1 in 1,000 patients, and the drug hasn’t gotten close to exceeding that rate. If it does, then the FDA’s language will probably get a lot more stern.