An Open-Label, Two-Arm Randomized Study to Characterize Flu-Like Symptoms in Relapsing Multiple Sclerosis Patients Transitioning From Current Interferon Beta Therapies to BIIB017

The primary objective of this study is to determine the proportion of participants with relapsing multiple sclerosis who experience new and/or increased flu-like symptoms (FLS) after transitioning from nonpegylated IFN-β therapies to peginterferon beta-1a (BIIB017). Secondary objectives are: to determine the severity and frequency (measured by flu-like symptom score [FLS-S]) of FLS in these participants; to determine the duration (measured in number of hours) of FLS in these participants; to determine the effect of BIIB017 on other participant-reported outcomes, including treatment satisfaction (measured with the Treatment Satisfaction Questionnaire for Medication [TSQM]) and disability status (measured with the Patient Determined Disease Steps [PDDS]) over a 56-week period; to determine whether interferon-related FLS result in missed days of work/daily activities (e.g., absenteeism); to assess the use of additional medications (in addition to current medications used to treat FLS) to relieve BIIB017-related FLS; to determine the incidence of adverse events throughout the study period; to characterize the immunogenicity profiles of participants switching from prior IFN-β therapy to BIIB017.