Two Years of Ocrelizumab Treatment in Black and Hispanic People with Multiple Sclerosis in <scp>CHIMES</scp> : A Single‐Arm Clinical Trial

OBJECTIVE: To evaluate the effectiveness and safety of ocrelizumab in self-identified black and Hispanic people with relapsing multiple sclerosis. METHODS: The Characterization of Ocrelizumab in Minorities with Multiple Sclerosis (CHIMES) trial, a prospective, open-label, single-arm, phase 4 study, intentionally recruited underrepresented populations in the US, Puerto Rico, and Kenya. Black and Hispanic people with relapsing multiple sclerosis aged 18-65 years with Expanded Disability Status Scale score 0-5.5 received ocrelizumab for 2 years. The primary endpoint was the proportion of participants with no evidence of disease activity in 3 components at week 48: protocol-defined relapse, 24-week confirmed disability progression, and disease activity on magnetic resonance imaging. RESULTS: , and Expanded Disability Status Scale score of 2.4 (SD 1.4). Genetic ancestry aligned with self-identified race or ethnicity. At week 48, 50.5% of CHIMES participants had no evidence of disease activity, including 94.5% free from 24-week confirmed disability progression, 95.1% free from relapse, 95.6% free from T1-contrast-enhancing lesions, and 52.7% free from new/enlarging T2 lesions. Serious adverse events were experienced by 8.2%, and 2.2% discontinued treatment. Infusion-related reactions were more frequent in Hispanic versus black participants (42.0% vs 29.2%), whereas gastrointestinal adverse events were more frequent in black versus Hispanic participants (23.0% vs 1.4%). INTERPRETATION: Ocrelizumab treatment controlled disease activity in black and Hispanic people with relapsing multiple sclerosis. Results were consistent with pivotal ocrelizumab trials, supporting ocrelizumab's effectiveness and tolerability in these populations. ANN NEUROL 2026.