Non-inferiority Study of Frexalimab Subcutaneous Administration Compared to Intravenous Administration in Adult Participants With Multiple Sclerosis

This is a randomized, open-label, parallel, Phase 3 study with 2-arms for treatment. The purpose of this study is to evaluate SC administration of frexalimab every 4 weeks (q4w) compared to IV administration of frexalimab q4w in male and female participants with RMS and nrSPMS (aged 18 to 60 years at the time of enrollment). People diagnosed with MS are eligible for enrollment as long as they meet all the inclusion criteria and none of the exclusion criteria. Study details include: The study intervention duration will be 48 weeks (12 months) for Parts A and B combined. Optional Part C will last until the initiation of a long term safety study for Frexalimab.The follow up duration after the end of study intervention (in case of discontinuation) will be 6 months. The number of scheduled visits (Parts A and B) will be 17 for participants receiving frexalimab SC or IV, with an on-site visit frequency of every month between Week 4 and Week 24 in Part A, then every 1 to 3 months in Part B, then every 6 months in Part C. Participants discontinuing treatment before the End of Study will have an additional 3 follow-up visits.