Now I ask the question....do you not think that Biogen's researchers were aware of this possible problem from the beginning? They knew what Tysabri's mechanism of action was and surely must have known of this possible danger. I believe that Dr. Lawrence Steinman, one of Tysabari's co-inventors, made several references to the long term use of the drug and this very type of danger. Biogen had an answer for him a few years ago...told him to stop "bad mouthing" the drug!

Harry