I am still amazed, that there was NO reaction at all, when the NEJM published two cases of PML which occurred with DMF (aka BG12), a week ago. Nothing, zilch, njet. Invcyte, for one dropped by over 10% when a tenuous association of Jakafi and a PML case was made. and BIIB has had its run up to say the least because of Tecfidera. Not even a blip upon the NEJM article....?
Only an issue if it occurs in a patient who tested negative for the JC virus prior to taking Tysabri. Otherwise it is a known risk with a pretty well established rate of occurrence and the impact on sales growth has already been factored into the stock.
A different formulation of the active ingredient in BG12 is used on psoriasis (and other illnesses). 2 (out of 10s of thousands) of the people on this, different medication, came down with PML. These people had other serious health issues and there is no idication that the medication caused PML in them, but SAEs must be reported by law in case there is a problem.