Inclusion Criteria:  A diagnosis of RMS in accordance with the revised 2017 McDonald Criteria. Expanded Disability Status Scale (EDSS) score of 0 - 5.5 at screening. For female participants of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and refrain from donating eggs. For male participants: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and refrain from donating sperm.  Exclusion Criteria:  Disease duration of > 10 years from the onset of symptoms and an EDSS score at screening < 2.0. Female participants who are pregnant or breastfeeding, or intending to become pregnant. Male participants who intend to father a child during the study. A diagnosis of Primary Progressive Multiple Sclerosis (PPMS) or non-active Secondary Progressive Multiple Sclerosis (SPMS). Any known or suspected active infection at screening, including but not limited to a positive screening tests for Hepatitis B and C, an active or latent or inadequately treated infection with tuberculosis (TB), a confirmed or suspected progressive multifocal leukoencephalopathy (PML). History of cancer including hematologic malignancy and solid tumors within 10 years of screening. Known presence of other neurological disorders, clinically significant cardiovascular, psychiatric, pulmonary, renal, hepatic, endocrine, metabolic or gastrointestinal disease. Any concomitant disease that may require chronic treatment with systemic corticosteroids or immunosuppressants during the course of the study. History of alcohol or other drug abuse within 12 months prior to screening. History of or currently active primary or secondary (non-drug-related) immunodeficiency, including known history of HIV infection. Inability to complete an MRI scan. Adrenocorticotropic hormone or systemic corticosteroid therapy within 4 weeks prior to screening. Receipt of a live-attenuated vaccine within 6 weeks prior to randomization. Any previous treatment with immunomodulatory or immunosuppressive medication without an appropriate washout period.