An advisory panel is set to make recommendations to the FDA this week about whether to allow multiple sclerosis drug Tysabri (natalizumab) back on the market.The advisory committee, which starts meeting Tuesday and will issue recommendations Wednesday, will discuss the drug’s risk-benefit profile and whether Tysabri should be available for at least some patients.Tysabri marketers Biogen Idec and Elan pulled it in February 2005 after two patients developed progressive multifocal leukoencephalopathy, or PML, a rare and often fatal brain infection. A third patient was later discovered to have PML. Two of the three patients died.In two of the cases, patients were also taking another Biogen drug, Avonex, at the same time, which led to speculation that Tysabri use alone might be less risky.“It is unclear for which patients the risk-benefit profile would be acceptable,” FDA staff said in a report released ahead of the advisory panel review, according to Reuters.The panel will also discuss a risk-management program that the companies have proposed should regulators sanction a return.