FDA permits marketing of first test for risk of rare brain infection in some people treated with Tysabri
Today, the U.S. Food and Drug Administration allowed marketing of the first test to help determine the risk for a rare brain infection called progressive multifocal leukoencephalopathy (PML) in people using the drug Tysabri (natalizumab) to treat multiple sclerosis (MS) or Crohn s disease (CD).