Poster Session II - A287 REAL-WORLD OUTCOMES OF MIRIKIZUMAB THERAPY FOR ULCERATIVE COLITIS

Abstract Background Mirikizumab, an IL-23p19 inhibitor demonstrated efficacy in inducing and maintaining remission in ulcerative colitis (UC) within clinical trials. Real-world evidence remains limited. Aims To evaluate the real-world effectiveness, durability, and safety of mirikizumab in UC patients. Methods A retrospective cohort study was conducted at a tertiary referral center. Adult UC patients initiating mirikizumab with ≥12 weeks follow-up (January 2023-August 2025). Primary outcome was corticosteroid-free (CSF) clinical remission (partial Mayo ≤2, no subscore >1) at weeks 12, 28, and 52. Secondary outcomes included CSF clinical response (≥2-point and ≥30% reduction in partial Mayo), mucosal healing (endoscopic Mayo ≤1), and adverse events. Results 40 patients were included: 55% female, median age was 34 years (IQR 21-51), and baseline Mayo 6.85 (SD 2.36). Nearly all (39/40) had prior advanced therapy exposure. CSF clinical remission was achieved in 23% at week 12, 30% at week 28, and 35% at week 52. CSF clinical response was 35%, 48%, and 39% respectively. Allowing for steroids at 12 weeks, clinical remission rate was seen in 25% and response in 52% of patients. No significant changes in CRP or fecal calprotectin were observed. Mucosal healing rates were 27% (3/11) at 6 months and 25% (1/4) at 12 months. Extended induction was given to 47.5% (19/40), who had lower but non-significant odds of CSF remission at 6 and 12 months. Among 32.5% (13/40) with prior ustekinumab exposure, no differences in remission rates were observed versus those without prior exposure. No serious adverse events occurred. Conclusions This real-world study of a highly treatment-experienced cohort shows CSF clinical remission rates at 12 weeks similar to phase III trials but lower rates at 52 weeks. Mirikizumab demonstrated acceptable safety. These findings support the effectiveness of mirikizumab for UC although further research is needed to identify optimal candidates. A287 Table 1: Baseline Characteristics Funding Agencies NoneNone