Primary Progressive Multiple Sclerosis (PPMS) Study of Bruton's Tyrosine Kinase (BTK) Inhibitor Tolebrutinib (SAR442168) (PERSEUS)

Inclusion Criteria: * 18 to 55 years of age inclusive * Diagnosis of PPMS according to the 2017 McDonald criteria * Expanded disability status scale (EDSS) score between 2.0 to 6.5 points, at screening inclusive * Positive cerebrospinal fluid oligoclonal bands and/or elevated Immunoglobulin G (IgG) index either during screening or documented previous history. * Contraceptive use consistent with local regulations for individuals participating in clinical studies * Participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: * Is not a woman of childbearing potential (WOCBP) or is a WOCBP and agrees to use an acceptable contraceptive method * the participant must not have access to ocrelizumab (eg, ocrelizumab not available on the national market or not reimbursed for the approved indication). * the participant must have access to and be eligible to be treated with ocrelizumab but: 1) does not tolerate it due to side effects or safety reasons; and/or 2) has failed ocrelizumab treatment due to perceived lack of efficacy Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply: * Participant has conditions that would adversely affect study participation such as short life expectancy. * Evidence of infection with human immunodeficiency virus (HIV), transplantation, progressive multifocal leukoencephalopathy (PML), active hepatitis B or C, active or latent tubercu…