Fourth 2008 PML case linked to Tysabri

Another Tysabri patient has contracted the potentially fatal brain infection PML, the fourth case this year. Biogen Idec and its Tysabri partner, Elan, notified regulators of the new diagnosis yesterday. The patient, located in Europe, had been taking Tysabri for 26 months as a monotherapy before developing PML, or progressive multifocal leukoencaphalopathy. The patient remains under a doctor's care.

It's a blow to Biogen and Elan, certainly, but many multiple sclerosis patients have proven steadfast about using Tysabri; though aware of the PML risk, they believe the benefits outweigh it. Some 18,000 patients have been using Tysabri for more than a year now, and more than 35,500 patients are on Tysabri, total. The drug is approved for use in MS and Crohn's disease.

Biogen's stock dropped 1.7 percent this morning, but analysts weren't overly worried: JP Morgan's Geoff Meacham told the Boston Globe that he wasn't surprised by the news and that he didn't expect the stock to fall further. But the earlier announcement of PML cases did dig into the stock price; Biogen was trading at over $70 before the August announcement, and now it's at $46.52. "Investors are becoming increasingly comfortable with the PML risk," Meacham told the Globe

- see the AP coverage
- read the Globe article