Xconomy.com -- Few doctors knew much about a rare brain infection called PML back in 2005, when two patients on a hot new multiple sclerosis drug from Biogen Idec and Elan died from the side effect. The infection, at the time, was generally considered a death sentence. But now with three years of data from more than 60,000 patients worldwide who have taken natalizumab (Tysabri) under strict monitoring by physicians, a new picture is emerging that shows PML is still very much a serious threat, but that it isn’t nearly as deadly as first feared.
