Ocrelizumab raises infection and hospitalization risk in older MS patients

A new study published in The Lancet Regional Health – Americas raises safety flags for older adults with multiple sclerosis (MS) receiving ocrelizumab, a widely used B-cell-depleting antibody therapy. Researchers at Massachusetts General Hospital analyzed records from 1,600 MS patients aged 55 and older — half treated with ocrelizumab, half never exposed to B-cell-depleting therapies — and found significantly elevated infection risks in the treated group.

After adjusting for confounders, ocrelizumab-exposed patients showed notably higher rates of both infection-related hospitalizations and overall infections. Urinary tract infections (UTIs) emerged as the dominant driver, particularly among women, who had a 97% higher UTI risk compared to men in the cohort.

By the Numbers:

• 67% higher infection-related hospitalization rate in the ocrelizumab group (IRR, 1.67)
• 42% higher overall infection rate (IRR, 1.42)
• 94% higher UTI risk with ocrelizumab exposure (IRR, 1.94)
• 91% of the sex-based infection disparity was attributed to UTIs

Why it matters: As ocrelizumab use grows among older MS patients — a population already at higher baseline infection risk — these findings highlight the need for proactive infection monitoring, especially for UTIs in women. Clinicians should weigh these risks carefully when prescribing, particularly in patients with higher disability scores or comorbidity burdens.