Shares in Elan fell 9 per cent this morning after it emerged that the US Food and Drug Administration (FDA) has extended its regulatory review of Elan's Tysabri by up to 90 days.
Elan and its partner Biogen Idec have been informed by the FDA that the agency requires additional time to review Tysabri's risk management plan.
Under this revised timeline, the companies anticipate action from FDA on or before June 28th, 2006.
The FDA was widely expected to accept the advisory panel's recommendation, and the delay in bringing it back to the market could disappoint investors.
But analysts remain confident that Tysabri will be cleared for release despite the latest delay. Elan has confirmed that no additional issues have been raised by the FDA and the delay is due to the agency's burden of work.
Elan is adamant that it can launch the product within weeks of getting re-launch approval from the FDA.
Biogen and Elan suspended Tysabri sales in February 2005 after three patients developed an infection called progressive multifocal leukoencephalopathy, or PML. Two of them died.
The advisory panel had said Tysabri should have mandatory controls to ensure patients know the risks and to quickly detect any new cases of a possibly fatal brain infection. All 12 members voted in favour of resuming sales.