This study investigates the use of frexalimab in adults living with multiple sclerosis, a condition where the body’s immune system attacks the protective covering of nerves. The purpose of the study is to compare two different ways of giving this medication to see if one is as effective as the other. One method involves intravenous administration, which means the medicine is delivered directly into a vein, while the other method is subcutaneous, meaning the medicine is injected into the fatty tissue just under the skin.

Participants will be monitored to observe how the drug moves through the body, a process known as pharmacokinetics, and to ensure the treatment is safe. The study will track how much of the medicine remains in the blood over time and check for any side effects. Researchers will also look at changes in the brain using MRI to identify Gd-enhancing T1 lesions, which are small areas of inflammation or damage that can be seen on specific scans. Additionally, the study will monitor any changes in physical ability to understand how the disease progresses over time.