To determine the discontinuation rates of rituximab (RTX) and ocrelizumab (OCR), and reasons for discontinuation in relapsing multiple sclerosis (RMS) patients. 

OCR and RTX are highly efficacious anti-CD20 monoclonal antibodies (CD20Mabs) used in the treatment relapsing multiple sclerosis (RMS). While these therapies are increasingly prescribed in RMS, there is a paucity of data examining discontinuation rates and reasons for discontinuation. 

A retrospective chart review was performed at two multiple sclerosis clinics in British Columbia, Canada. RMS patients were included if they were treated with at least one infusion of OCR or RTX between February 2017 and March 2023. Patients were excluded if they were on concurrent immunotherapy (other than pulse steroids for acute relapses) or if they received autologous hematopoietic stem cell transplantation. 

881 RMS patients were included in the study (478 on OCR and 403 on RTX). 141/881 (16.0%) patients stopped CD20Mabs over 2337 patient-years. Reasons for discontinuation included: side effects (33.3%), insurance coverage (17.0%), new clinical or radiological disease activity (11.3%), and progressive disease (5.7%). The most common side effects leading to discontinuation were infusions reactions (17/47, 36.1%), infections (9/47, 19.1%), and allergy (9/47, 19.1%). At 12, 24, and 36 months, discontinuation rates for OCR were 3.5%, 8.2%, and 12.5%, whereas discontinuation rates for RTX were 6.4%, 14.8%, and 22.2%, respectively (p = 0.0089). Treatment with RTX was the only variable associated with treatment discontinuation on Cox regression analysis (Hazard ratio 1.72, 95% confidence interval 1.20 – 2.45).

In our retrospective cohort study, side effects and insurance coverage were the most common reasons for discontinuation of CD20Mabs. Our findings suggest that RMS patients treated with RTX may be more likely to stop therapy and discontinue treatment earlier compared to OCR-treated patients.