Tysabri and Brain Infections

Tysabri, a highly touted multiple sclerosis drug marketed by Biogen Idec Inc. and Elan Plc, is drawing renewed scrutiny from European drug regulators who’ve witnessed an increase in cases where Tysabri users are contracting a rare but serious brain infection known as progressive multifocal leukoencephalopathy, or PML. The regulators are concerned about potential higher instances of brain infection corresponding to longer use of Tysabri in multiple sclerosis patients.
According to the Wall St. Journal, European regulators are in discussions with the FDA in the United States about the problem. Last month, the FDA updated the warning on Tysabri noting that PML risk appears to be commensurate with longer term use of the drug. Tysabri had been temporarily suspended in 2005 after 3 cases of PML were reported. The drug re-entered the market after 18 months. Thus far, 13 cases of PML have been reported by the company in patients who’ve used Tysabri to treat MS. At this point, Tysabri appears more problematic in patients who take the drug in prolonged fashion.