SUSTAIN

Treatment tested

• Daclizumab

  Interleukin-2 receptor inhibitor

Other measures (8)

Key Inclusion Criteria * Must have documented diagnosis of RRMS (McDonald 2010 Criteria) at screening [Polman 2011]. * Must have been treated with natalizumab for at least the 12 months prior to screening and have not missed 2 or more consecutive scheduled doses. * Must be naïve to daclizumab and other forms of daclizumab such as Zenapax® prior to enrollment. * Must have a confirmed Expanded Disability Status Scale (EDSS) score of 0 to 5.5, inclusive, at screening. * Female participants of childbearing potential must practice effective contraception from Day -1 and be willing and able to continue contraception for duration of the study. Key Exclusion Criteria * Current participation in another investigational study. * Diagnosis of primary progressive, secondary progressive, or progressive relapsing MS (as defined by Lublin and Reingold) [Lublin 2014]. * Females breastfeeding, pregnant, or planning to become pregnant; or women who have a positive pregnancy test result during screening. * History of drug or alcohol abuse (as defined by the Investigator) within 1 year prior to screening. * History of severe hypersensitivity (e.g., anaphylaxis or anaphylactoid reactions) to the active ingredient or any of the excipients. * History of severe opportunistic infections (including progressive multifocal leukoencephalopathy (PML)) or any clinically significant, cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic (other than MS), dermatologic, psychiatric, and renal, or other major disease, as determined by the Investigator. * Discontinued natalizumab due to suspicion of PML. * Known active malignancies (participants with cutaneous basal cell carcinoma that has been completely excised prior to study entry remain eligible). * The participant is using another MS therapy concomitantly. * Known history of human immunodeficiency virus (HIV). * Positive test result for Hepatitis C virus (test for hepatitis C virus antibody [HCV Ab]) or hepatitis B virus (test for hepatitis B surface antigen [HBsAg] and/or hepatitis B core antibody [HBcAb]). * The participant has been treated with immunosuppressive or immunomodulating treatments including mitoxantrone, azathioprine, methotrexate, cyclophosphamide, or mycophenolate mofetil. NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

The primary objective of the study is to evaluate the effects of treatment with daclizumab on the proportion of participants relapse-free at 6 months in Relapsing-Remitting Multiple Sclerosis (RRMS) participants, who switched from treatment with natalizumab to daclizumab due to safety concerns. The secondary objectives of this study in this study population are to evaluate the effects of daclizumab on the following: 1) Multiple Sclerosis (MS) relapse activity including the annualized relapse rate (ARR) and the proportion of participants experiencing relapses requiring hospitalization and/or steroid treatment; 2) MS-related outcomes measured using magnetic resonance imaging (MRI); 3) Safety and tolerability in participants previously treated with natalizumab.