Long-term real-world effectiveness and safety of mirikizumab in ulcerative colitis: 52-Week results from an expanded international two-center retrospective cohort study.

BACKGROUND: Mirikizumab, a selective interleukin-23p19 inhibitor, has demonstrated efficacy in randomized controlled trials for moderate-to-severe ulcerative colitis (UC). However, long-term real-world data remain limited, particularly in treatment-experienced populations. OBJECTIVES: To evaluate the 52-week real-world effectiveness and safety of mirikizumab in a treatment-experienced UC cohort. DESIGN: Two-center international retrospective observational cohort study of adults with active UC initiating mirikizumab. METHODS: This study expands a previously published 12-week real-world cohort from the same centers, adding patients and extending follow-up to 52 weeks. The primary outcome was clinical remission (SCCAI ≤2) at week 52 using non-responder imputation. Secondary outcomes included clinical response, corticosteroid-free remission, and drug persistence at weeks 12, 26, and 52, as well as safety. RESULTS: The cohort included 120 patients with prior anti-TNF, vedolizumab, and JAK inhibitor exposure in 75.8%, 75.0%, and 42.5%, respectively. Clinical response rates were 67.5%, 52.3%, and 41.3% at weeks 12, 26, and 52, with corresponding remission rates of 14.2%, 19.8%, and 28.3% (modified NRI: 35.6%). Corticosteroid-free remission at 52 weeks was 26.1%. Drug persistence at 52 weeks was 64.6% (95% CI 54.9-72.7%), without significant differences by prior biologic exposure class. Among 60 patients (50.0%) receiving extended induction, week-26 remission was lower than in standard induction recipients (10.7% vs. 29.1%; p=0.018). Adverse events occurred in 13 patients (10.8%), leading to discontinuation in 5 (4.2%). CONCLUSION: In this large treatment-experienced real-world UC cohort, mirikizumab achieved 52-week clinical remission in 28.3% and drug persistence of 64.6%, with no new safety signals identified, supporting its role across lines of therapy in UC.