Multiple Sclerosis Drug Tysabri Removed From Market

BOISE, Idaho, March 1, 2005 — The multiple sclerosis (MS) drug nataluzimab (Tysabri) was withdrawn from the U.S. market yesterday while the FDA and the drug's manufacturer, Biogen Idec, investigate two serious reactions reported with its use.

Tysabri was recently approved to reduce relapses in people with MS. Biogen Idec voluntarily removed Tysabri from the market after one person taking the drug died of progressive multifocal leukoencephalopathy (PML), a rare but serious neurologic disease. Another possible case of PML in a person taking Tysabri has been reported. The relationship between Tysabri and PML is not clear. However, because PML is often fatal, the drug has been voluntarily taken off the market and the use of Tysabri in clinical trials has been stopped until researchers know more about whether there is a relationship between Tysabri and PML.