Effectiveness and safety of mirikizumab in multirefractory ulcerative colitis: analysis from a real-world cohort

Mirikizumab is a selective anti-IL-23 monoclonal antibody approved for moderate-to-severe ulcerative colitis (UC). Evidence regarding its efficacy mostly derives from registration trials, as real-world data in multi-refractory populations remain limited.

We conducted an observational study including UC patients treated with mirikizumab. Clinical activity was assessed using the partial Mayo (pMayo) score at baseline, Week12 (W12), and Week24 (W24). Urgency, biomarkers, endoscopic activity and safety were evaluated. Steroid-free clinical remission (SFCR) was defined as pMayo≤1 without corticosteroids; clinical response as ≥3-point or ≥30% reduction. Changes over time were analyzed using paired non-parametric tests; logistic regression identified predictors of remission.

One-hundred-twenty-three highly treatment-expierenced patients were included (median 3 prior advanced therapies, IQR 2-4). Most patients (89.0%) continued extended IV induction after W12. SFCR was achieved in 25.2% (31/123) at W12 and 31.3% (30/96) at W24, while clinical response occurred in 70.7% and 67.7%, respectively. Bowel urgency improved at W12 and W24 (p<0.001). Adverse events occurred in 20.3% of patients; the colectomy rate was 4.9%. Higher baseline pMayo and prior JAKi exposure were associated with lower remission.

Mirikizumab showed encouraging effectiveness and safety in multirefractory UC. Prior JAKi exposure emerged as a potential negative predictor of remission; this hypothesis-generating signal warrants validation.