This clinical trial is focused on studying Relapsing Multiple Sclerosis, a condition where the immune system mistakenly attacks the protective covering of nerves, causing communication problems between the brain and the rest of the body. The study will evaluate a new treatment called LY3541860, which is being compared to a placebo. The aim is to see if LY3541860 can slow down the formation of new brain lesions, which are areas of damage in the brain, in people with this type of multiple sclerosis.

Participants in the study will receive either the new treatment or a placebo. The treatment involves an injection, and the study will monitor the participants over a period to observe any changes in the number of new brain lesions. These lesions are detected using MRI scans, a type of imaging that helps doctors see inside the body without surgery. The study will help determine if LY3541860 is effective in reducing the occurrence of these lesions.

In addition to LY3541860, the study will also use Gadoteric Acid, a contrast agent used in MRI scans to improve the clarity of the images. This agent is injected into the body to help highlight certain areas during the scan. The study will provide valuable information on the safety and effectiveness of LY3541860 in treating relapsing multiple sclerosis.