Efficacy and Safety Study of Frexalimab (SAR441344) in Adults With Nonrelapsing Secondary Progressive Multiple Sclerosis

Inclusion Criteria: * Participant must have a previous diagnosis of RRMS in accordance with the 2017 revised McDonald criteria. * Participant must have a current diagnosis of SPMS in accordance with the clinical course criteria revised in 2013 endorsed by an Adjudication Committee. * Participant must have documented evidence of disability progression observed during the 12 months before screening. Eligibility will be analyzed by an Adjudication Committee. * Absence of clinical relapses for at least 24 months. * The participant must have an EDSS score at screening from 3.0 to 6.5 points, inclusive. * Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. * For patients eligible to be treated with siponimod: 1) does not tolerate it due to side effects or safety reasons, or 2) has failed siponimod treatment due to perceived lack of efficacy, or 3) has declined siponimod treatment. Exclusion 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 immunoglobulin levels (IgG and/or IgM) below the lower limits of normal (LLN) at Screening or a history of primary hypogammaglobulinemia. Patients with a history of secondary hypogammaglobulinemia induced by anti-C20 monoclonal antibodies (eg, ocrelizumab, ofatumumab, ublituximab, rituximab) may be considered for study inclusion provided their immunoglobulin levels are within the normal limits (WNL) at time of Screening. * 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 sensitivity to any of the study interventions, or components thereof, or has a drug or other allergy that, in the opinion of the Investigator, contraindicates participation in the study. * The participant was previously exposed to frexalimab. The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.