Humoral immune response to COVID-19 mRNA vaccines in patients with relapsing multiple sclerosis treated with ofatumumab

Background: There are limited data available regarding the impact of ofatumumab, an anti-CD20 B-cell−depleting monoclonal antibody for relapsing multiple sclerosis (RMS), on vaccination response. The study objective was to assess humoral immune response (HIR) to non-live coronavirus disease 2019 (COVID-19) messenger RNA (mRNA) vaccination in patients with RMS treated with ofatumumab. Methods: This was an open-label, single-arm, multicenter, prospective pilot study of patients with RMS aged 18−55 years who received 2 or 3 doses of a COVID-19 mRNA vaccine after ≥1 month of subcutaneous ofatumumab (20 mg/month) treatment. The primary endpoint was the proportion of patients achieving HIR, as defined by local laboratory severe acute respiratory syndrome coronavirus-2 qualitative immunoglobulin G assays. Assay No. 1 was ≥14 days after the second or third vaccine dose. Assay No. 2 was 90 days thereafter. Results: Of the 26 patients enrolled (median [range] age: 42 [27−54] years; median [range] ofatumumab treatment duration: 237 [50−364] days), HIR was achieved by 53.9% (14/26; 95% CI: 33.4 − 73.4%) at Assay No. 1 and 50.0% (13/26; 95% CI: 29.9 − 70.1%) at Assay No. 2. Patients who received 3 vaccine doses had higher HIR rates (Assay No. 1: 70.0% [7/10]; Assay No. 2: 77.8% [7/9]) than those who received 2 doses (Assay No. 1: 46.7% [7/15]; Assay No. 2: 42.9% [6/14]). Of patients aged <40 years without previous anti-CD20 therapy, HIR was achieved by 90.0% (9/10) at Assay No. 1 and 75.0% (6/8) at Assay No. 2. No serious adverse events were reported. Conclusion: Patients with RMS treated with ofatumumab can mount HIRs following COVID-19 vaccination. A plain language summary, infographic and a short video summarizing the key results are provided in supplementary material. Clinical trial registration: ClinicalTrials.gov: NCT04847596 (https://clinicaltrials.gov/ct2/show/NCT04847596)