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Treatment tested

• Daclizumab

  Interleukin-2 receptor inhibitor

Other measures (43)

Key Inclusion Criteria: * Must be a subject currently participating in Study 205MS301 (NCT01064401), or subject currently participating in Study 205MS203 (NCT01051349) or Study 205MS302 (NCT01462318) who has completed End of Study Visit (Week 96 or later). * Women of childbearing potential must practice effective contraception during the study and be willing and able to continue contraception for 4 months after their last dose of study treatment. Key Exclusion Criteria: * Any subject who permanently discontinued study treatment in Study 205MS301 (NCT01064401), Study 205MS203 (NCT01051349) or Study 205MS302 (NCT01462318) prior to the end of the study treatment period, or had an Early Termination visit in Study 205MS301, Study 205MS203 (NCT01051349) or Study 205MS302 (NCT01462318). * Any significant change in the subject's medical history that would preclude administration of BIIB019, including laboratory tests or a current clinically significant condition that, in the opinion of the Investigator, would have excluded the subject's participation in Study 205MS301 (NCT01064401), Study 205MS203 (NCT01051349) or Study 205MS302 (NCT01462318). The Investigator must re review the subject's medical fitness for participation and consider any factors that would preclude treatment in this Study 205MS303. NOTE: Other protocol-defined inclusion/exclusion criteria may apply.

The primary objective of the study is to assess the safety and tolerability of long-term treatment with BIIB019 (Daclizumab High Yield Process; DAC HYP) monotherapy in participants with relapsing remitting multiple sclerosis (RRMS) who completed Study 205MS301 (NCT01064401), Study 205MS203 (NCT01051349) or Study 205MS302 (NCT01462318). Secondary objectives of this study in this study population are as follows: To describe MS-related outcomes, including MS relapse, disability progression, MS lesion formation, and participant-reported impact of MS, following long-term treatment with DAC HYP To assess the long-term immunogenicity of DAC HYP administered by prefilled syringe (PFS) To assess the safety, tolerability, and efficacy of switching to DAC HYP in participants previously on long-term treatment with interferon β-1a (Avonex) in Study 205MS301(NCT01064401).