Biogen Idec has applied to the U.S. Food & Drug Administration and the European Medicines Agency to extend the indication for Tysabri (natalizumab) to include first-line use in MS. The first-line indication would be for patients with relapsing MS who had tested negative for JC virus antibodies. At present, the indication for use of natalizumab is as a second-line treatment option for patients who fail prior therapy or have rapidly evolving MS.