Prescribing instructions for Elan and Biogen's drug Tysabri should note cases of a serious brain infection in patients using it as their sole treatment for multiple sclerosis, US health regulators said tonight.
The Food and Drug Administration said it was working to amend the Tysabri label after two cases of the potentially fatal brain infection, progressive multifocal leukoencephalopathy (PML), were reported in Europe. The companies disclosed the cases in July.
"While the two patients who developed PML were on monotherapy, the FDA still believes that Tysabri monotherapy may confer a lower risk of PML than when Tysabri is used together with other immunomodulatory medications," the FDA said in a statement on its website.
Biogen spokeswoman Shannon Altimari said changes would be made to an existing "black box" warning on Tysabri and elsewhere on the drug's label.
The company plans to provide an update on the condition of the two patients at the European Federation of Neurological Societies in Madrid on Tuesday, Altimari said.
Elan officials could not be immediately reached for comment.