The future of Elan's MS drug Tysabri will be decided over the next two days by the US drug regulator after it conducts a review of the drug.
An advisory committee of the Federal Drug Administration (FDA) will assess whether the drug should be allowed to return to the market given the risk of side effects.
Most analysts expect the FDA to clear the way for Tysabri's return - but with conditions. Documents released by the FDA yesterday showed that the FDA is impressed by Tysabri's efficacy for the treatment of MS but remains cautious about its side effects.
Elan and Biogen withdrew Tysabri from the US market in February 2005 after two patients developed a rare brain disorder. A third patient was later discovered to have the disorder, known as progressive multifocal leukoencephalopathy, or PML. Two of the three patients died.
Biogen and Elan have proposed a risk management programme that would allow the companies to keep studying patients on Tysabri for at least five years.
Shares in Elan jumped as much as 10 per cent today before being suspended ahead of the meeting.
The FDA meeting is timetabled to begin at 1pm Irish time today but will not make any recommendations until tomorrow, with a final decision expected by March 29th.