WASHINGTON — U.S. health officials cleared the way Monday for multiple sclerosis drug Tysabri to return to the market with restrictions, after 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 Inc. and distributed by Elan Corp., had developed progressive multifocal leukoencephalopathy. Two of them died.
Food and Drug Administration officials, who had faced calls from patients to revive sales, said they still knew 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," said Dr. Steven Galson, director of the FDA's Center for Drug Evaluation and Research.
Tysabri should be used alone and not with other drugs that suppress the immune system, the agency said, and patients should try another therapy first.
The rare decision by regulators to allow a withdrawn drug back on the market failed to boost the companies' shares, which sank on the news.
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.
"The new label suggests that demand for Tysabri could be less than our recently adjusted forecast," Sanford C. Bernstein & Co. analyst Geoff Porges said in a research note.
Renewed sales are seen as key to helping Elan recover from a brush with bankruptcy in 2002.
RBC Capital Markets analyst Jason Kantor estimated that U.S. sales would reach $36 million in 2006, $439 million in 2007 and $806 million in 2008.
Elan shares closed down $2.46, or 13%, at $16.52. Biogen shares fell $2.32, or 4.9%, to $45.39.
Both companies said Tysabri would give MS patients another option to treat their debilitating disease.
"There continues to be a significant unmet medical need where Tysabri will be an important treatment option," Elan Chief Executive Kelly Martin said.