LTS18002

Treatment tested

• Frexalimab

Compared with

• Teriflunomide

  Dihydroorotate dehydrogenase inhibitor

Placebo or sham

• Matched placebo for comparator teriflunomide
• Matched placebo for test product frexalimab

Other measures (9)

Inclusion: - Participants with RMS or nrSPMS who completed, on IMP, the Phase 2 ACT16877 study, or one of the four Phase 3 frexalimab studies in MS indication (EFC17919A and EFC17919B, EFC17504, EFC18098), or planned Phase 2 biomarker ASY22814. - All Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. - The participant must be capable of giving signed informed consent Exclusion: - If IMP discontinuation criteria are met as per guidance - Individuals accommodated in an institution because of regulatory or legal order; prisoners or participants who are legally institutionalized. - The participant is at risk for or has a persistent chronic, active (including fever ≥38°C and clinically unstable), recurring systemic infection or opportunistic infections (eg, PML See Appendix in protocol) as judged by the Investigator. - Notably low IgG levels, defined as a level that is 20% below the LLN, and/or notably low IgM level, defined as a level 10% below the LLN. - Participants who developed clinically relevant cardiovascular, hepatic, endocrine, neuropsychiatric or other major systemic disease making implementation of the protocol or interpretation of the study results difficult or that would put the participant at risk by participating in the extension study, as judged by the Investigator. - Clinical evidence, suspicion or significant risk for thromboembolic events, as well as myocardial infarction, stroke, and/or antiphospholipid syndrome and any participants requiring antithrombotic treatment. - The participant is no longer deriving a therapeutic/clinical benefit in the opinion of the Investigator - Suicidal risk as per C-SSRS: if a participant scores “yes” on items 4 or 5 of the Suicidal Ideation Section, or “yes” on any item of the Suicidal Behavior Section. - Continued need for/chronic use of a prohibited concomitant medication - Any country-related specific regulation that would prevent the participant from entering

To determine the long-term safety and tolerability of frexalimab IV and SC administrations