OBSERVE

Treatment tested

• Midazolam

  GABA-A receptor; anion channel positive allosteric modulator

• Caffeine
• S-warfarin
• Vitamin K
• Omeprazole

  Potassium-transporting ATPase inhibitor

• Dextromethorphan
• Daclizumab

  Interleukin-2 receptor inhibitor

Other measures (11)

Key Inclusion Criteria: * Must have a confirmed diagnosis of RRMS according to McDonald criteria and previous cranial magnetic resonance imaging demonstrating lesion(s) consistent with MS * Must have a baseline Expanded Disability Status Scale (EDSS) between 0.0 and 5.0, inclusive * Must have had 1 or more clinical relapses within the previous 2 years * Women of child bearing potential must be willing to practice effective contraception during the study and 4 months after the last dose Key Exclusion Criteria: * Other chronic disease of the immune system, malignancies, acute urologic, pulmonary, gastrointestinal disease * Female subjects who are currently pregnant or breastfeeding Key Inclusion criteria for 3-Year Treatment Extension: To be eligible for participation in the 3-year treatment extension, participants must meet the following eligibility criteria at the time of reinitiation of DAC HYP: * Must have been compliant with the 205MS302 (NCT01462318) protocol during the initial 24-week treatment period and the 20-week washout period in the opinion of the Investigator * Must resume DAC HYP treatment ≤12 weeks after completion of the washout period (i.e., ≤12 weeks after their Week 44 visit). * Participants who are currently receiving an approved IFN ß preparation must discontinue interferon (IFN) ß treatment at the time of reinitiation of DAC HYP dosing (no washout is required). Key Inclusion criteria for the TP-DI Sub-study: To be eligible for participation in the TP-DI Sub-Study, subjects must meet the following eligibility criteria at the Screening Visit at Week 40: * Must have been compliant with the 205MS302 (NCT01462318) protocol during the initial 24-week treatment period and through Week 40 of the 20-week washout period in the opinion of the Investigator. * Must agree to resume DAC HYP treatment ≤12 weeks after completion of the washout period (i.e., ≤12 weeks after their Week 44 visit). * Must have normal liver function test results (total bilirubin ≤1.5 × upper limit of normal (ULN), alanine aminotransferase/aspartate aminotransferase ≤2 × ULN, and prothrombin time/partial thromboplastin time ≤1.2 × ULN). * Must have normal renal function as estimated creatinine clearance >60 mL/min (Cockcroft-Gault formula). NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

The primary objective of the study is to assess the immunogenicity of Daclizumab High Yield Process (DAC HYP) 150 mg administered every 4 weeks by subcutaneous (SC) injection using the pre-filled syringe (PFS) in participants with relapsing-remitting multiple sclerosis (RRMS). The secondary objectives of this study are to characterize the pharmacokinetics (PK) of DAC HYP following single and multiple doses of DAC HYP administered by the PFS in a subset of participants with RRMS and to evaluate the effect of DAC HYP on the PK of probe drugs for cytochrome P450 (CYP) isoenzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A).