The purpose of each study is to independently measure the annualized relapse rate (ARR) with administration of frexalimab compared to a daily oral dose of teriflunomide in male and female participants with relapsing forms of multiple sclerosis (aged 18 to 55 years at the time of enrollment). People diagnosed with relapsing forms of multiple sclerosis are eligible for enrollment as long as they meet all the inclusion criteria and none of the exclusion criteria. Study details include: * This event-driven study will have variable duration depending on the recruitment rate, the event rate, the study discontinuation rate and the 12-month minimum treatment duration. Different participants will have different study durations. The last participant randomized will have at least 12 months of study duration, and assuming a 28-month recruitment period, the first participant randomized will have 40 months or longer of study duration. * The study intervention duration will vary similarly as the study duration. * The assessment of scheduled visits will include 1 common end of study \[EOS\] visit and 3 follow-up visits) with a visit frequency of every 4 weeks for the first 6 months and then every 3 months.
Inclusion Criteria: * The participant must have been diagnosed with RMS according to the 2017 revision of the McDonald diagnostic criteria. * The participant has an EDSS score ≤5.5 at the first visit (Screening Visit) * The participant must have at least 1 of the following prior to screening: * ≥1 documented relapse within the previous year OR * ≥2 documented relapses within the previous 2 years, OR * ≥1 documented Gd enhancing lesion on an MRI scan within the previous year. * Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. Exclusion Criteria: * The participant has been diagnosed with PPMS according to the 2017 revision of the McDonald diagnostic criteria * The participant has a history of infection or may be at risk for infection: * The presence of psychiatric disturbance or substance abuse. * History, clinical evidence, suspicion or significant risk for thromboembolic events, as well as myocardial infarction, stroke, and/or antiphosholipid syndrome and any participants requiring antithrombotic treatment. * Current hypogammaglobulinemia defined by Ig levels below the LLN at Screening or a history of primary hypogammaglobulinemia. * A history or presence of disease that can mimic MS symptoms, such as, but not limited to neuromyelitis optica spectrum disorder, systemic lupus erythematosus, Sjogren's syndrome, acute disseminated encephalomyelitis, and myasthenia gravis. * The participant has had a relapse in the 30 days prior to randomization. * The participant has contraindication for MRI, ie, presence of pacemaker, metallic implants in high risk areas (ie, artificial heart valves, aneurysm/vessel clips), presence of metallic material (eg, shrapnel) in high risk areas, known history of allergy to any contrast medium, or history of claustrophobia that would prevent completion of all protocol scheduled MRI scans. The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.