The primary outcome of the study is to evaluate the cumulative area under the concentration time curve (AUC) over 2 weeks, as measured by AUC from time 0 to 336 hours post dose (AUC0-336h), for serum concentrations of BIIB017 and Rebif.

The secondary outcomes are to evaluate the maximum observed serum concentrations (Cmax) of BIIB017 and Rebif and to evaluate the safety and tolerability of BIIB017 and Rebif over 2 weeks in healthy volunteers.

Key Inclusion Criteria:

- Must have a body mass index of 19 to 30 kg/m2, inclusive, and minimum body weight of 45.0 kg at Screening and Day -1

Key Exclusion Criteria:

• History or positive test result at Screening for human immunodeficiency virus, hepatitis C virus antibody or current hepatitis B infection (defined as positive for hepatitis B surface antigen [HBsAg] and/or hepatitis B core antibody [HBcAb])
• History of premalignant and malignant disease including solid tumors and hematologic malignancies
• Known allergy to any interferon or any component of BIIB017
• Prior treatment with any investigational drug within the 30 days prior to Day 1, or within 5 half-lives of the drug, whichever is longer

NOTE: Other protocol defined Inclusion/ Exclusion criteria may apply.