Safety of Avonex Treatment in Multiple Sclerosis Patients With Neutralizing Antibodies to Interferon Beta Therapy

This is a multi-centre, prospective, open label, non-comparative phase IV trial. Eligible patients will receive treatment with IFN-beta-1a AVONEX® 30 mcg i.m. once weekly for 12 months.The patients will be examined clinically and NAb titres will be performed at screening and after 12 months. Adverse event source verification will be performed during the documentation period.