Predictors of Relapse Following Transition to Ofatumumab in Relapsing-Remitting Multiple Sclerosis

Introduction Ofatumumab (OFA) is an emerging therapy for relapsing-remitting multiple sclerosis (RRMS), but the impact of prior disease-modifying therapy (pDMT) on outcomes after switching is unclear. Objectives To evaluate predictors of first-year relapse after switching from selected pDMTs to OFA in adults with RRMS enrolled in the MSBase Registry. Results Among 866 patients (median EDSS 2.5), 10.5% experienced a relapse in the first year on OFA. Switching from fingolimod was associated with higher relapse risk compared to switching from injectable therapies (HR 1.89, 95% CI 1.03–3.44, p=0.038). Higher EDSS at OFA initiation (HR 1.25, 95% CI 1.09–1.43, p=0.001) and relapse in the year prior to pDMT cessation (HR 1.75, 95% CI 1.01–3.03, p=0.045) also predicted relapse. Washout period duration was not associated with relapse in the overall cohort, but longer washout among fingolimod switchers increased relapse risk (HR 1.34, 95% CI 1.01–1.79, p=0.044). Conclusion Relapse after switching to OFA is influenced by baseline disability, recent relapse, and prior fingolimod use. Shorter washout may reduce relapse risk in fingolimod switchers. These findings support tailored monitoring and further research to optimise treatment transitions in RRMS.