A Retrospective Evaluation of Ocrelizumab and Rituximab Discontinuation in a Real-World Patient Cohort

ABSTRACT Background: Ocrelizumab (OCR) and rituximab (RTX) are anti-CD20 monoclonal antibodies (CD20Mabs) used in the treatment of relapsing multiple sclerosis (RMS). While both are effective at reducing relapses and new MRI lesions in clinical trials, real-world data on discontinuation rates and reasons for stopping therapy are limited. Methods: This observational retrospective chart review included patients from two MS clinics in British Columbia, Canada. RMS patients treated with at least one infusion of OCR or RTX between January 2017 and March 2023 were included. Primary outcomes were reasons for discontinuation and discontinuation rates, with a secondary outcome of time to discontinuation. Results: In total, 881 RMS patients were included, with 478 on OCR and 403 on RTX. A total of 16.9% of patients on OCR and 14.9% on RTX discontinued therapy over 1643 and 694 patient-years, respectively ( p = 0.46). Reasons for discontinuation included: side effects (33.3%), insurance coverage (17.0%) and clinical or radiological disease activity (11.3%). Discontinuation rates at 12, 24 and 36 months were 3.5%, 8.2% and 12.5% for OCR, and 6.4%, 14.8% and 22.2% for RTX, respectively ( p = 0.0089). Median time to discontinuation was 21 months on OCR and 11.5 months on RTX ( p < 0.0001). On Cox regression analysis, treatment with RTX was the only variable associated with discontinuation (hazard ratio 1.72, 95% CI 1.20–2.45). Conclusion: Discontinuation rates of CD20Mabs were low, and the most common reason for stopping was side effects. Although not designed for comparison, our study suggests RMS patients may persist longer on OCR than RTX.