CAMBRIDGE, Mass.--(BUSINESS WIRE)--Biogen Idec (NASDAQ: BIIB) today announced enrollment of the first patient in a Phase III, randomized, double-blind, placebo-controlled trial designed to evaluate the efficacy and safety of PEGylated interferon beta-1a (BIIB017) in patients with relapsing multiple sclerosis (RMS). The trial, called ADVANCE, will determine the efficacy of PEGylated interferon beta-1a in reducing relapse rates in patients with RMS.