FDA Questions Tysabri for Crohn's Disease

Tysabri was approved in the U.S. in November 2004, then pulled from the market in February 2005 after Biogen and Elan received two reports of a rare, often fatal brain infection called progressive multifocal leukoencephalopathy, or PML.

Later, they learned of one PML case in a clinical trial testing Tysabri for Crohn's disease. No additional cases have been detected. Earlier this month, EU regulators cited the risk of PML and their concerns about effectiveness as the reasons for rejecting Tysabri for Crohn's disease.

The FDA approved the return of Tysabri in June 2006 as an MS treatment, and the drug has been available for about 12 months, albeit with many restrictions. Elan reported Thursday that the Tysabri partners sold $72.1 million during the second quarter, with the U.S. providing about two-thirds of the total.