Dataset from A Randomized, Blinded, Placebo-Controlled, Serial-Cohort, Multiple Ascending Dose Study of the Safety, Tolerability, and Pharmacokinetics of BIIB033 in Subjects With Multiple Sclerosis

The main purpose of the study is to evaluate the safety, tolerability, and pharmacokinetic
profile of two intravenous infusions of BIIB033 administered two weeks apart in subjects with
MS.

Approximately 42 MS subjects are planned to be enrolled in the study in 7 separate groups
(i.e., 6 subjects per group). Each subsequent group will be administered a higher dose of
BIIB033. Before a higher dose group is allowed to start, a Drug Safety Review Committee will
review all safety data from previous groups enrolled, as well as data from another study
where BIIB033 is being administered to healthy volunteers (215HV101).