Shares of Ireland's Elan tumbled in overnight trading after the Boston Globe reported that a fourth patient taking its new MS drug Tysabri may have contracted a rare and often fatal brain disease known as PML. The report said that the fourth unconfirmed case involved a woman taking Tysabri with another MS drug -- Avonex. Two of the three confirmed cases of PML involve patients taking a combined regimen of Tysabri and Avonex, leading to some speculation that the drugs may return to the market with instructions to avoid Avonex while taking Tysabri. Elan, which partnered with Biogen Idec on the drug, has continued to manufacture the drug in the hope of a speedy reintroduction.
- read this story from RTE on Tysabri