Bloomberg -- Biogen Idec Inc. (BIIB) has identified high-risk patients taking its multiple sclerosis drug Tysabri who have a 1 in 100 chance of developing a potentially deadly brain infection from the medicine. By analyzing the length of Tysabri use, previous treatments and results of a blood test for antibodies to the virus that causes the infection, doctors may spot patients with less than a 1 in 10,000 risk of progressive multifocal leukoencephalopathy, or PML, the analysis found. The drug’s U.S. label says the PML risk is 1.5 in 1,000 after two years of treatment.
