A Phase 3b, 12-month, Open-label, Multicenter Study to Evaluate the Efficacy and Safety of BIIB019, Daclizumab, in Subjects With Relapsing-Remitting Multiple Sclerosis (RRMS) Switching From Natalizumab (SUSTAIN)

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.