Biogen Reports 10th PML Case With Tysabri

Biogen Idec(BIIB Quote) reported Friday that a tenth multiple sclerosis patient being treated with Tysabri was diagnosed with a serious brain infection.

The latest case of progressive multifocal leukoencephalopathy (PML) occurred outside the U.S. in a patient on Tysabri therapy for 30 months. Four Tysabri patients on therapy for more than 30 months have now contracted PML, including the last three reported cases.

This is raising concerns that the risk of a multiple sclerosis patient contracting PML increases with longer duration of Tysabri therapy. The overall incident rate of PML is still very small and Biogen Idec has presented scientific data disputing the notion that PML risk increases with longer Tysabri use. ...