Planned dose reduction of ocrelizumab in relapsing-remitting multiple sclerosis: a single-centre observational study

Ocrelizumab, a humanised anti-CD20 monoclonal, is a highly effective treatment for relapsing-remitting multiple sclerosis (RRMS). The long-term safety of B-cell depletion in RRMS, however, is uncertain and there are no data on dose reduction of ocrelizumab as a risk mitigation strategy. This study aimed to evaluate the effectiveness and safety of reducing ocrelizumab dose from 600 to 300 mg in patients with RRMS.

Data were collected through the Townsville neurology service. Following the standard randomised controlled trial regimen of 600 mg every 6 months for 2 years, sequential patients consented to dose reduction to 300 mg every 6 months. Patients were included if they were diagnosed with RRMS and received at least one reduced dose of ocrelizumab. Relapse, disability progression, new MRI lesions, CD19⁺ cell counts and immunoglobulin concentrations were analysed.

A total of 35 patients, treated with 177 full and 107 reduced doses, were included. The mean follow-up on reduced dose was 17 (1-31) months. We observed no relapses or new MRI activity in the cohort receiving the reduced dose, accompanied by persistent CD19+B cell depletion (≤0.05×10⁹/L). Mean IgG, IgA and IgM levels remained stable throughout the study. No new safety concerns arose.

In this single-centre observational study, dose reduction of ocrelizumab from 600 to 300 mg every 6 months after 2 years appeared to maintain efficacy in terms of new inflammatory disease activity. A randomised trial may be warranted to confirm this and explore the impact of dose reduction on long-term safety.