The Food and Drug Administration, in a notice to reporters, said it scheduled a briefing for later Monday on the approval of Tysabri for Crohn's disease. The drug already is sold as a therapy for multiple sclerosis.
Biogen shares rose more than 1.5 percent Monday, while shares of Elan were more than 0.5 percent higher.
Elan said the FDA approved Tysabri for certain adults with moderately to severely active Crohn's disease. The companies expect Tysabri will be available to Crohn's patients by the end of February, Elan said in a statement.
Tysabri was temporarily withdrawn from the market in 2005 amid three cases of serious brain infection. The drug is sold now with warnings, distribution limits and other restrictions.
Crohn's disease is a bowel inflammation that causes potentially disabling abdominal pain, weight loss, fever and rectal bleeding.