New data on progressive multifocal leukoencephalopathy with Tysabri

Biogen Idec and Elan Corp. announced new data on the incidence of progressive multifocal leukoencephalopathy (PML) associated with the use of multiple sclerosis treatment natalizumab (Tysabri). According to the companies, no new cases of PML have been reported since the re-launch in the United States and launch internationally in July 2006. As of the end of March 2008, about 26,000 patients were receiving the therapy worldwide. The data were presented this week at the 60th Annual Meeting of the American Academy of Neurology (AAN) in Chicago. The companies also presented findings from the