Multicentre retrospective real-world evidence study evaluating the effectiveness and safety of mirikizumab in patients with moderately to severely active ulcerative colitis.

Introduction: Mirikizumab (MIRI), a selective IL-23 p19 inhibitor, has demonstrated efficacy in randomised trials in moderate to severe ulcerative colitis (UC), but real-world data remain limited, particularly in highly treatment-exposed populations. Aim: To assess the real-world effectiveness and safety of MIRI in adults with moderately to severely active UC. Material and methods: This retrospective multicentre study included 257 adults with UC initiating MIRI before 31 January 2026 across 21 Polish centres. Induction consisted of intravenous MIRI 300 mg at weeks 0, 4, and 8, with optional extension to week 24 in cases of insufficient response. Disease activity was assessed at baseline and at weeks 12 and 24 using clinical, endoscopic, and laboratory parameters. Safety was evaluated by recording adverse events (AE) and serious adverse events (SAE). Results: Most patients had prior exposure to advanced therapy, and 54.1% underwent extended induction. Significant improvement was observed at weeks 12 and 24 across all parameters. Among evaluable patients, clinical remission was 31.7% at week 12 and 41.8% at week 24, while clinical response was 76.2% and 79.3%, respectively. Endoscopic remission was 9.5% and 18.5%, whereas endoscopic response was 67.1% and 64.8%, respectively. Corticosteroid-free clinical remission was 23.1% and 26.4%. AE occurred in 9.1% and 14.1% of patients, and SAE in 2.6% and 6.6%. Conclusions: In this large real-world study with predominantly advanced therapy-exposed UC, MIRI was associated with significant clinical, endoscopic, and biochemical improvement through weeks 12 and 24, with a favourable safety profile.