A Study of LY3541860 in Adult Participants With Relapsing Multiple Sclerosis

Inclusion Criteria: * Participants must meet criteria for relapsing forms of multiple sclerosis, including relapsing-remitting multiple sclerosis based on the 2017 revision of the McDonald diagnostic criteria (Thompson et al. 2018) with a relapsing course (RMS) activity according 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 to screening. * 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 of McDonald 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 days prior 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 abnormali…