Biogen Idec Inc. and Elan Corp. plc, the co-owners of multiple sclerosis drug Tysabri, have sent a recommendation to the U.S. Food and Drug Administration and the European Medicines Agency to update the labeling of the drug in order to clarify the risk of a rare but potentially fatal brain infection.

The two companies have proposed that labeling of Tysabri include anti-JC Virus antibody status as a factor related to the risk of progressive multifocal leukoencephalopathy (PML), the name of the brain infection.

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