Non-inferiority study of frexalimab subcutaneous administration compared to intravenous administration in adult participants with multiple sclerosis.

Other illness

• The participant has a history of infection or may be at risk for infection.
• Presence of psychiatric disturbance or substance abuse
• History, clinical evidence, suspicion or significant risk for thromboembolic events, as well as myocardial infarction, stroke, and/or antiphospholipid syndrome and any participants requiring antithrombotic treatment.
• Current hypogammaglobulinemia defined by Ig levels (IgG and/or IgM) below the LLN at screening or a history of primary hypogammaglobulinemia
• A history or presence of disease that can mimic MS symptoms.

Other

• The participant has been diagnosed with primary progressive MS according to the 2017 revision of the McDonald diagnostic criteria.
• Fever within 28 days of the Screening Visit
• The participant has a contraindication for MRI.

• Group A (RMS) - The participant must be 18 to 55 years of age, inclusive, at the time of signing the informed consent.
• Group B (nrSPMS) - The participant must have an EDSS score between 3.0 and 6.5 points, inclusive, at the first visit (Screening Visit).
• Participants from Group A and Group B are eligible to be included in the study only if all of the following criteria also apply: - Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.
• Group A (RMS) - The participant must have been diagnosed with RMS in accordance with the 2017 revised McDonald criteria.
• Group A (RMS) - The participant must have an Expanded Disability Status Scale (EDSS) score of ≤5.5 at the first visit (Screening Visit).
• Group A (RMS) - The participant must have at least 1 of the following prior to screening: ≥1 documented relapse within the previous year OR ≥2 documented relapses within the previous 2 years, OR ≥1 documented Gd enhancing lesion on an MRI scan within the previous year.
• Group B (nrSPMS) - Participant must have a previous diagnosis of RRMS in accordance with the 2017 revised McDonald criteria.
• Group B (nrSPMS) - The participant must be 18 to 60 years of age, inclusive, at the time of signing the informed consent.
• Group B (nrSPMS) - The participant must have a current diagnosis of SPMS in accordance with the clinical course criteria revised in 2013.
• Group B (nrSPMS) - The participant must have documented evidence of disability progression observed during the 12 months before screening.
• Group B (nrSPMS) - The participant must have an absence of clinical relapses for at least 24 months.