Effectiveness and safety of mirikizumab in patients with moderate-to-severe ulcerative colitis: the miri real multicenter study

Background & Aims Mirikizumab, an IL-23 p19–targeting monoclonal antibody, is approved for moderate-to-severe ulcerative colitis (UC). Real-world evidence on its effectiveness and safety remains limited. We evaluated its effectiveness and safety in a real-world setting. Methods This retrospective multicenter study included adult UC patients treated with mirikizumab at 5 Italian centers (June 2024-October 2025), with ≥24 weeks of follow-up. The primary outcome was clinical remission (CR, pMS ≤ 2 with rectal bleeding 0) at week(w)12. Secondary outcomes included intestinal ultrasound (IUS) remission, endoscopic remission, bowel urgency (BU) remission, fecal calprotectin (FC) normalization, and safety profile. Results A total of 236 patients (60.2% male; median age 47) were included. 77.5% had prior exposure to advanced therapy. Mirikizumab significantly reduced pMS at w12 and w24 (both P < .001), with clinical remission in 46.6% and 55.5%, respectively. Mayo endoscopic score improved at both timepoints (P < .01 and P < .001) with 38% achieving endoscopic remission at w24. IUS remission was nonsignificant at w12 but significant at w24 (P < .0001). BU and FC improved at both timepoints (P < .001). Remission rates were similar in biologic-naive and biologic-exposed patients. Discontinuations were uncommon, adverse events were infrequent and non-serious, and liver tests showed no clinically relevant changes. Conclusions In this real-world multicenter cohort, mirikizumab was associated with meaningful improvements across clinical, endoscopic, biochemical, and ultrasound outcomes, with low discontinuation rates and a favorable safety profile through 24 weeks. These findings support the effectiveness of selective IL-23 inhibition in routine care, including in patients with prior exposure to advanced therapies.