This clinical trial is focused on studying the effectiveness and safety of a new treatment for multiple sclerosis, specifically for its relapsing forms. Multiple sclerosis is a condition where the immune system mistakenly attacks the protective covering of nerves, leading to communication problems between the brain and the rest of the body. The study will compare a new medication called frexalimab (also known by its code name SAR441344) with an existing treatment called teriflunomide, which is available as AUBAGIO 14 mg film-coated tablets. Frexalimab is administered as a solution for injection, while teriflunomide is taken orally in tablet form.

The purpose of the study is to assess how well frexalimab works compared to teriflunomide in reducing the frequency of relapses in people with relapsing forms of multiple sclerosis. Participants in the study will receive either frexalimab, teriflunomide, or a placebo, which is a substance with no active medication. The study will last for a period of up to 160 weeks, during which participants will be monitored for any changes in their condition, including the number of relapses they experience and any side effects they may encounter.

Throughout the study, various assessments will be conducted, such as MRI scans to detect changes in the brain, and tests to evaluate cognitive function and overall impact on daily life. The study will also monitor for any adverse events or reactions to the medications. The goal is to gather comprehensive data on the safety and effectiveness of frexalimab as a potential new treatment option for individuals with relapsing forms of multiple sclerosis.