Elan shares fell sharply on the Dublin stock market today despite the decision by US regulators to clear the company's Tysabri drug for a return to the market.
Elan shares fell 12.4 per cent at the opening in Dublin this morning to €12.93, having fallen by a similar amount on the New York Stock Exchange last night.
Analysts said calling for patients to first try other MS drugs could curb demand for Tysabri, which had been on track to be a potential billion-dollar-a-year seller before the withdrawal.
Analysts once thought Tysabri could reach sales of $2 billion a year or more. Most projections have now been reduced, though some analysts still expect sales eventually to exceed $1 billion.
US health officials cleared the way yesterday for multiple sclerosis drug Tysabri to return to the market with restrictions, following its withdrawal last year when it was linked to a rare but potentially fatal brain disease.
Three patients taking the drug, made by Biogen Idec and distributed by Elan, had developed progressive multifocal leukoencephalopathy (PML).
Two of them died. Food and Drug Administration (FDA) officials, who faced calls from patients to revive sales, said they still know very little about how to predict, prevent or treat the brain disease.
"We are certain that patients are willing to take this risk because of the potential benefits of the drug," Dr Steven Galson, director of the FDA's Center for Drug Evaluation and Research, told reporters.
Tysabri should be used alone and not with other drugs that suppress the immune system, the agency said, but patients should try another MS therapy first.
All doctors who prescribe Tysabri and patients who take it will have to enroll in a monitoring programme.
The drug, which was priced at more than $20,000 a year before it was withdrawn, will now be available only through authorised infusion centres. Those centres must go through a checklist with each patient before each monthly infusion, in an effort to ensure that patients are eligible for the drug and to detect early signs of the rare side effect.
As another safeguard, patients must receive an MRI scan before treatment to help differentiate MS symptoms from those linked to the brain disease, the FDA said.