The purpose of this study is to understand differences in responses to those beginning treatment with ublituximab (Briumvi) as prescribed for Multiple Sclerosis by their treating provider. The study consists of three visits where some questions are asked about experience with Multiple Sclerosis and blood samples are drawn for genetic research and immune cell counts. While taking part in this study, some of the possible risks include those related to having blood drawn, risk of loss of confidentiality and risks related to genetic research.

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.