The primary objective of this study is to characterise the pharmacokinetics (PK) of BIIB017 (Peginterferon Beta-1a) administered as a single 125 μg subcutaneous (SC) dose in Japanese and Caucasian adult healthy participants. The secondary Objective is to assess the safety and tolerability of a single 125 μg subcutaneous (SC) dose of BIIB017 in Japanese and Caucasian adult healthy participants.