SYNERGY

Treatment tested

• Opicinumab

  Leucine-rich repeat and immunoglobulin-like domain-containing nogo receptor-interacting protein 1 inhibitor

• Interferon beta-1a

  Interferon alpha/beta receptor agonist

Placebo or sham

• Placebo

Other measures (4)

Key Inclusion Criteria: * Diagnosis of relapsing remitting MS (RRMS) or onset of secondary progressive MS (SPMS) * RRMS and SPMS subjects must have evidence of ongoing disease activity within 12 months of enrollment. * All male and female subjects of childbearing potential must practice effective contraception during the study and be willing and able to continue contraception for at least 6 months after their last dose of study treatment Key Exclusion Criteria: * A MS relapse that has occurred within the 90 days prior to Day 1/Baseline and/or the subject has not stabilized from a previous relapse prior to Screening * Previous history of clinically significant disease. * Plans to undergo elective major procedures/surgeries at any time during the study. * Treatment with any investigational MS drugs within 3 weeks or 5 times the half life (whichever is longer) prior to Day 1/Baseline * RRMS subjects with any history of inadequate response to any approved interferon β preparation * History of human immunodeficiency virus (HIV), hepatitis C virus antibody, or hepatitis B virus * History or evidence of drug or alcohol abuse within 2 years prior to randomization Note: Other protocol defined inclusion/exclusion criteria may apply.

The primary objective of the study is to evaluate the efficacy of BIIB033 in participants with active relapsing multiple sclerosis (MS) when used concurrently with Avonex. Secondary objectives of this study in this study population are to assess the safety, tolerability, and population pharmacokinetics of BIIB033 when used concurrently with Avonex.