A Study of LY3541860 in Adult Participants With Relapsing Multiple Sclerosis

Inclusion Criteria:

• Participants must meet criteria for relapsing forms of multiple sclerosis, includingrelapsing-remitting multiple sclerosis based on the 2017 revision of the McDonalddiagnostic criteria (Thompson et al. 2018) with a relapsing course (RMS) activityaccording to Klineova and Lublin 2018.

• Participants must have 1 of these:

• at least 1 documented relapse within the previous year

• at least 2 documented relapses within the previous 2 years, or

• at least 1 active GdE brain lesion on an MRI scan in the past 180 days prior toscreening.

• Have an Expanded Disability Status Scale (EDSS) score of less than or equal to (≤) 5.5 at screening and randomization.

Exclusion Criteria:

• Have had a diagnosis of:

• primary progressive multiple sclerosis (MS) according to the 2017 revision ofMcDonald diagnostic criteria (Thompson et al. 2018), or

• nonactive secondary progressive MS ( Klineova and Lublin 2018).

• Meet criteria for neuromyelitis optica spectrum disorder (Wingerchuk and Lucchinetti 2022).

• Have a history of clinically significant central nervous system (CNS) disease.

• Have had a confirmed relapse with systemic corticosteroid administration <30 daysprior to randomization.

• Have more than 20 active GdE brain lesions on screening MRI scan.

• Have received any of these medications or treatments.

• Have a current or recent acute, active infection.

• Have current serious or unstable illnesses.

• Have any other clinically important abnormality at screening or baseline.