FDA allows Tysabri sales

FDA says Biogen Idec and Elan Corp. can resume marketing Tysabri, a monoclonal antibody used to treat patients with relapsing forms of multiple sclerosis. Tysabri was approved by the agency in November 2004 but was pulled off the market in February 2005, after three patients in the drug's clinical trials developed progressive multifocal leukoencephalopathy, a rare viral infection of the brain. Two of the cases were fatal. FDA allowed a trial of Tysabri to resume in February 2006, following a reexamination of the patients who had participated in the previous clinical trials that confirmed there were no additional cases of PML. In March, FDA advisers recommended that the agency allow Tysabri sales to resume, with restrictions.