Tysabri natalizumab: Post-marketing study data

As of Sept. 8, FDA reported that there have been 13 confirmed cases of progressive multifocal leukoencephalopathy (PML) in patients receiving Tysabri monotherapy for MS since the drug was relaunched in the U.S. and its first international approval in 2006. FDA also said the risk for developing PML appears to increase with the number of Tysabri infusions received. The overall rate of developing PML with Tysabri therapy in patients who have received at least 1 infusion is <1/1,000 patients and 0.4-1.3/1,000 patients in those who have received at least 24 infusions. Additionally, the agency said that it is not requiring changes regarding PML to Tysabri's label or to the drug's risk management plan at this time. At the end of June, Biogen Idec reported on its website that 61,200 patients had been treated with Tysabri (see BioCentury, Aug. 3). ...