Safety and Efficacy Extension Study of Daclizumab High Yield Process (DAC HYP) (BIIB019) in Participants Who Have Completed Study 205MS202 (NCT00870740) to Treat Relapsing Remitting Multiple Sclerosis

Primary Objective is to assess the safety of extended treatment with Daclizumab High Yield Process (DAC HYP, BIIB019) monotherapy in participants with relapsing remitting multiple sclerosis (RRMS). Secondary Objective is to assess the long-term immunogenicity of DAC HYP and to assess the durability of response to DAC HYP in preventing multiple sclerosis (MS) relapse, slowing disability progression, and reducing new MS lesion formation in this study population.

This study will provide participants who complete Study 205MS202 (NCT00870740) with the option to receive continued open-label Daclizumab High Yield Process (DAC HYP) monotherapy and to evaluate the long-term safety, efficacy, and immunogenicity of DAC HYP monotherapy in participants with relapsing remitting multiple sclerosis (RRMS). Approximately 60 to 100 participants will be enrolled into an optional open-label, 16-week autoinjector substudy at a selected subset of sites which will run concurrently during the main study, and will evaluate the systemic exposure and local tolerability of subcutaneous administration of DAC HYP by autoinjector. The 2013-2014 trivalent influenza vaccine will be offered to all eligible participants as an optional substudy to assess the effect of DAC-HYP treatment on the immune response to vaccination,

Eligibility Criteria:
Main Study Eligibility:

Key Inclusion Criteria:

* Ability to understand the purpose and risks of the study and provide signed and dated informed consent and authorization to use protected health information (PHI) in accordance with national and local subject privacy regulations.
* Subjects who have completed 52 weeks in Study 205MS202 (NCT00870740) and were compliant with the 205MS202 protocol in the opinion of the Investigator.
* 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:

* Subjects with any significant change in their medical status from the previous study that would prelude administration of Daclizumab High Yield Process (DAC HYP) as determined by the Investigator including laboratory tests or a current clinically significant condition that, in the opinion of the Investigator, would have excluded the subject's participation in the 205MS201 (NCT00390221) or 205MS202 (NCT00870740) studies. The Investigator must re-review the subject's medical fitness for participation and must consider any diseases that would preclude treatment.
* Any subject who has permanently discontinued study treatment in Study 205MS202 (NCT00870740) due to an adverse event.
* Current enrollment in any investigational drug study other than Study 205MS202 (NCT00870740).
* Ongoing treatment with any approved or experimental disease-modifying treatment for multiple sclerosis.
* For subjects currently taking valproic acid, carbamazepine, lamotrigine, or phenytoin:

  * Subjects treated with any of these agents for fewer than 6 months prior to study entry are excluded from study participation unless they discontinue the agent(s) prior to study entry.
  * Subjects treated with 2 or more of these agents for more than 6 months prior to study entry are excluded from study participation unless they reduce to ≤1 agent prior to study entry.
  * Subjects who have had dose escalations of one of these agents within the 6 months prior to study entry are excluded from study participation unless they revert to a previous dose that had been used for at least 6 months prior to study entry or unless they discontinue the agent prior to study entry
* Subjects who are currently receiving treatment with isoniazid, propylthiouracil, or nimesulide at the time of study entry and are not able to discontinue the agent or change to an alternative medication allowed by the protocol.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.