A Dose-Frequency Blinded, Multicenter, Extension Study to Determine the Long-Term Safety and Efficacy of PEGylated Interferon Beta-1a (BIIB017) in Subjects With Relapsing Multiple Sclerosis

The primary objective of this study is to evaluate the long-term safety and tolerability of peginterferon beta-1a (BIIB017) in participants originally treated in Study 105MS301 (NCT00906399) who continue peginterferon beta-1a treatment. The secondary objective of this study is to describe long-term multiple sclerosis (MS) outcomes in participants originally treated in Study 105MS301 (NCT00906399) who continue peginterferon beta-1a treatment.