A Study to Evaluate Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of Multiple Doses of Natalizumab (BG00002) Administered Subcutaneously to Japanese Participants With Relapsing-Remitting Multiple Sclerosis

Key Inclusion Criteria: * Must have had a diagnosis of RRMS, as defined by the revised 2017 McDonald's criteria. All other possible neurologic diagnoses must have been reasonably excluded by means of laboratory and/or imaging studies, in the opinion of the investigator. * Must have had an EDSS score between 0.0 and 5.5, inclusive. * Must have had screening MRI or documentation of an MRI within the participant's medical record within 12 months of the screening visit that revealed 3 or more T2 hyperintense lesions consistent with MS. * Was born in Japan, and biological parents and grandparents were of Japanese origin. Key Exclusion Criteria: * Evidence of current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection within 14 days prior to Screening, between screening and baseline visit, or at baseline visit, including but not limited to a fever (temperature \> 37.5 degrees Celsius \[°C\]), new and persistent cough, breathlessness, or loss of taste and/or smell. * Have close contact within 14 days prior to Day 1 with a SARS-CoV-2 positive individual. * Diagnosis of primary progressive MS or secondary progressive MS. * An MS exacerbation (relapse) within 30 days prior to enrolment or, in the opinion of the investigator, the participant not having stabilized from a previous relapse prior to enrolment (Day 1). * The participant is unable to have a brain MRI scan (e.g., a participant with a metal clip to repair a cerebral aneurysm). * Previous exposure to natali…