Background: Black, African American (AA) and Hispanic/Latino (HA) patients with multiple sclerosis (MS) have greater disease severity and faster progression than patients of Northern European ancestry. However, these populations are vastly underrepresented in clinical trials, owing to poor access to care as well as cultural, economic and other institutional enrollment barriers. Ocrelizumab (OCR), an anti-CD20 therapy that depletes B cells, reduced the rates of disease activity and progression in patients with relapsing MS (RMS) and primary progressive MS in pivotal studies; however, participation of the above populations was <10%. Objectives: To investigate the efficacy and safety of OCR in AA and HA patients with RMS (2017 McDonald criteria) who meet the US prescribing information criteria in an open-label, single-arm, Phase IV clinical study. Methods: An industry-sponsored collaborative approach rooted in addressing the needs of AA and HA MS patients and bridging the knowledge gaps about the efficacy and safety of ocrelizumab in these populations. Results: Key differences between CHIMES (NCT04377555) and other MS trials are as follows: CHIMES was developed in collaboration with MS patients, patient advocacy groups and investigators with a focus on AA and HA patients with MS. Inclusion criteria allow for 150 participants with specific, well-controlled, pre-existing comorbidities; excluding these comorbidities has disproportionately limited AA and HA patient qualification in other trials. OCR was chosen because AA patients with MS may have greater B-cellmediated pathology. Written materials and the study website are available in English and Spanish and reviewed by a patient panel to ensure they are easy to understand. To enable early results, the primary endpoint is disease activity, defined by the proportion of RMS patients achieving NEDA3 (clinical relapses, confirmed disability progression or MRI activity) at the end of Year 1. All patients may participate in a second-year extension. Conclusions: Findings from CHIMES are expected to improve the current understanding of MS in AA and HA patients, with the ultimate goals of accumulating prospective, high quality data and contributing to improving the standard of care for these traditionally underserved populations.