The FDA will convene a panel of outside experts March 7 to decide whether to allow multiple sclerosis drug Tysabri (natalizumab) back on the market.The agency said the panel will discuss Tysabri’s “possible return to market and risk management plans,” according to a report in Dow Jones Newswires.The drug’s marketers, Biogen Idec and Elan, removed Tysabri in February from the US market after two patients developed a rare brain disorder, called progressive multifocal leukoencephalopathy (PML), and one died. In subsequent studies of the drug for Crohn’s disease, a third was found to have PML.Executives from the companies expect a final ruling from the FDA by the end of March. If it is allowed to return to market, Tysabri’s label likely would have to include a warning that its use has been linked to PML.This week Biogen Idec and Elan said a recently completed safety evaluation of more than 3,000 Tysabri patients yielded no new confirmed cases of PML.