Approximately 100 weeks
This is a Phase 2, randomized, double-blind, placebo-controlled 2 parallel-arm study to assess the effect on serum neurofilament light chain (sNfL), safety and tolerability of oral SAR443820 compared to placebo in male and female participants aged 18 to 60 years with relapsing-remitting multiple sclerosis (RRMS), secondary progressive multiple sclerosis (SPMS) (relapsing or non-relapsing), or primary progressive multiple sclerosis (PPMS) followed by an open-label long-term extension period.~The total study duration is approximately 100 weeks and includes the following:~4-week screening period 48-week double-blind treatment period (Part A) 48-week open-label long-term extension period (Part B)