Effectiveness and safety of mirikizumab in ulcerative colitis: real-world data from the Latium Net

OBJECTIVE: To evaluate the effectiveness and safety of mirikizumab in patients with ulcerative colitis in clinical practice. METHODS: We conducted a retrospective, multicenter cohort study across five Italian inflammatory bowel disease centers. Patients initiating mirikizumab between November 2024 and May 2025 were included. The primary endpoint was steroid-free clinical remission (SFCR) at 12 weeks, defined as the absence of rectal bleeding and near-normal stool frequency without corticosteroids. Secondary outcomes included clinical response (≥30% improvement in stool frequency and rectal bleeding), biochemical response (normalisation of fecal calprotectin (FCP) and C-reactive protein (CRP)), and safety (any adverse events). Follow-up at 24 weeks was assessed when available. Subgroup analyses were performed according to prior exposure to biologics (including ustekinumab) and induction regimen. RESULTS: A total of 95 patients were included (mean age 49.9±16.9 years; 50.5% male); 12.6% were biologic naïve and 17 (17.9%) received extended induction. At week 12, 43.2% of patients (41/95) achieved SFCR, 61.1% (58/95) clinical response, and 32/95 (33.7%) biochemical remission. SFCR rates were similar between biologic-naïve and biologic-experienced patients (42.6% vs 43.8%, p=0.906). SFCR rates were 36.2% and 88.2% in patients receiving extended and standard induction, respectively (p=0.002). At week 24, prior ustekinumab exposure was associated with numerically lower SFCR, although this difference was not statistically significant (38.5% vs 73.7%; OR=0.22, 95% CI 0.05 to 1.01, p=0.052). Changes in biomarkers were not statistically significant at week 12 (CRP Δ-0.08 mg/dL, p=0.464; FCP Δ-249 µg/g, p=0.127). Three patients discontinued treatment due to lack of efficacy. No adverse events were observed. CONCLUSION: Mirikizumab demonstrated meaningful clinical effectiveness and a favourable safety profile in a real-world setting, including in biologic-experienced patients.