Elan shares decline 5.8% on new US FDA call for stronger warning on Tysabri

Irish drugmaker Elan saw its share price drop 5.8% to 5.05 euros, after it was revealed that the US Food and Drug Administration had found that the risk of a potentially fatal brain disorder with the firm's multiple sclerosis drug Tysabri (natalizumab) increases as patients receive more infusions and called for stronger warnings. The agency did, however, reiterate its views that the benefits for MS patients associated with the drug still outweigh the risks.

The prescribing information for Tysabri, co-marketed with US biotechnology company Biogen Idec - originator of the drug - will be updated to warn about the higher risk of use of the drug over time. The FDA said the warning is based on 31 confirmed cases of progressive multifocal leukoencephalopathy (PML) since its market re-introduction in 2006, having been withdrawn previously - in February 2005 - due to its links with the condition.

A spokeswoman for Biogen, which saw its shares dip less than 0.1% on Friday to $53.06, said that there is nothing new in the FDA announcement and that the company has already updated the label to reflect these changes, following discussions with the agency last fall.