It is unclear whether Biogen and Elan's multiple sclerosis drug Tysabri may raise the risk of a rare, life-threatening brain infection when used alone, US Food and Drug Administration staff said today.
"It is unclear for which patients the risk-benefit profile would be acceptable," the FDA staff said in a report released ahead of an advisory panel review of the drug that starts tomorrow.
The companies should implement a mandatory programme to monitor risks if the drug is allowed to return to the market, the staff recommended.
Tysabri sales were suspended in February 2005.