The main purpose of the study is to find out if patients treated with remibrutinib may experience fewer Multiple Sclerosis relapses (also called clinical attacks, exacerbations or flare ups) than patients treated with teriflunomide (also known as Aubagio). Teriflunomide is an approved medication for the treatment of relapsing MS. This clinical study will have two parts. The first part is the masked part in which neither you nor your doctor know if you receive remibrutinib or teriflunomide and will last up for a maximum of up to 30 months (~2.5 years). This is followed by an Extension Part which will have treatment and safety follow up periods; during the treatment period remibrutinib treatment is provided to all participants who had completed core part of study for a maximum of up to 5 years.

A number of veterans suffer from multiple sclerosis (MS), a devastating and debilitating disease for which there is not cure or significant treatment. The only therapy available is immunomodulatory, but does not treat the neurodegeneration. The studies proposed in this application will develop therapeutic strategies and identify a drug that ameliorates inflammation as well as neurodegeneration in the disease. Thus, the effect of this drug will not only help veterans with MS, but will also benefit individuals with the disease in general.