The risk of a potentially fatal brain disorder with Elan's multiple sclerosis drug Tysabri increases as patients receive more infusions, US health officials warned today.
The prescribing instructions for Tysabri, co-marketed by Biogen and Elan, will be updated to warn about the higher risk over time, the Food and Drug Administration said.
The FDA said the warning is based on 31 confirmed cases of progressive multifocal leukoencephalopathy (PML), a brain infection that can be fatal.
Spokespeople for Biogen and Elan were not immediately available for comment.
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Shares of Elan fell 31 cents to €5.05 today on the Dublin market.