Comparative Effectiveness and Safety of Rituximab Versus Ocrelizumab in Relapsing–Remitting Multiple Sclerosis: A Finnish Population‐Based Matched Cohort Study

Background B‐cell–depleting anti‐CD20 therapies are among the most effective disease‐modifying treatments for relapsing–remitting multiple sclerosis (RRMS). Rituximab (RTX) is widely used off‐label, while ocrelizumab (OCR) is approved for RRMS; yet comparative real‐world evidence between the two remains limited. Methods We conducted a retrospective registry‐based cohort study using the Finnish MS Registry, including adult RRMS patients treated with RTX or OCR between 2018 and 2024 at two university hospitals. Propensity score matching (1:1) was applied to balance baseline characteristics. Primary outcomes were annualized relapse rate (ARR) during follow‐up and relapse‐free survival. Secondary outcomes included MRI activity, disability progression, adverse events, and longitudinal plasma immunoglobulin G (IgG) levels. Results Of 636 screened patients, 191 met inclusion criteria and 112 patients (56 RTX, 56 OCR) were included after matching. Median follow‐up was 3.1 years for RTX and 2.6 years for OCR. ARR was low and similar in both groups (mean 0.03), and relapse‐free survival did not differ (log‐rank p = 0.95; HR 0.95, 95% CI 0.21–4.33). MRI activity remained largely stable, with no significant differences in T2 lesion changes. Adverse events were infrequent and mild. IgG declined modestly in both groups (mean−13%), with values below the reference range in 4.5% of patients and no association with infections. No disease reactivation was observed among patients switching from OCR to RTX. Conclusions In this population‐based Finnish real‐world study, RTX and OCR demonstrated comparable effectiveness and safety in RRMS, supporting RTX as a rational alternative to OCR in routine clinical practice.