To Örebro University

Introduction: ofatumumab is a human CD20 monoclonal antibody targeting B-cells and a small population of CD20+ T-cells. The treatment is administered once a month (after initial dosing) with subcutaneous injections for patients with Remitting Multiple Sclerosis (RMS). ofatumumab is included in the Swedish post-market surveillance study “Immunomodulation and Multiple Sclerosis Epidemiology substudy 12” (IMSE 12).

Objectives/Aims: To assess safety and effectiveness of ofatumumab with focus on 12 months treatment outcomes.

Methods: Data on Extended Disability Status Scale (EDSS), Multiple Sclerosis Severity Scale (MSSS), Symbol Digit Modalities Test (SDMT), Multiple Sclerosis Impact Scale (MSIS-29), and relapses and Adverse Events (AEs) were collected from the nationwide Swedish Neuro Registry (NeuroReg). Effectiveness measures and relapse rates were assessed using Wilcoxon Signed Rank Test.

Results: A total of 111 ofatumumab exposed Persons with MS (PwMS) have been included in IMSE 12 since the launch in March 2021. In this cohort 93.7% remained with ofatumumab while 7 patients (6.3%) discontinued treatment at any time after initiation. The most common reasons for discontinuation were Adverse Event (unspecified, n=2) and Other Reasons (unspecified, n=2). All the AEs reported to the Swedish Medical Products Agency will be shown.In this cohort most PwMS (25.5 %) had switched from rituximab, 24.5% from natalizumab, 11.8% from dimethyl fumarate and 7.8% had been treatment naïve prior treatment with ofatumumab.51 patients have so far been treated with ofatumumab for ⩾12 months. The ⩾12month cohort demonstrated a non-significant trend for improvement in mean EDSS, MSSS, and a stable SDMT score compared with baseline. The mean annual relapse rate (ARR) decreased significantly (p<0.05) during first year of treatment (0.02) compared to the ARR (0.14) one-year prior treatment initiation.

Conclusion: PwMS exposed for ⩾12 months to ofatumumab display clinical stability and a tendency for improvement in EDSS, MSSS and SDMT compared with baseline. Longer observation times will be needed to assess the effectiveness and safety of ofatumumab beyond 12month exposure.