Abstract Background Mirikizumab (MRK) is a monoclonal antibody targeting the IL-23 p19 subunit that has demonstrated efficacy in pivotal trials for moderate-to-severe ulcerative colitis (UC). Real-world data in patients with multi-refractory disease are still limited. We aimed to assess the short- and mid-term effectiveness, safety, and treatment persistence of MRK in routine clinical practice. Methods We conducted a retrospective observational study of consecutive adult UC patients who initiated MRK between June 2024 and June 2025 and completed induction. The primary endpoint was symptomatic remission at week 12. Secondary endpoints included clinical remission at week 24, biochemical remission (faecal calprotectin 250 µg/g) at weeks 12 and 24, adverse events, and treatment persistence. Symptomatic remission and clinical response were defined according to PRO2 (stool frequency and rectal bleeding subscores). Results Thirty-three patients were included (24% women), with a median age of 58 years and a median disease duration of 15.6 years. Most patients had prior exposure to advanced therapies: 85% had received anti-TNF agents, 64% vedolizumab and 58% ustekinumab; 60.6% had been treated with three and 24.2% with four previous advanced lines. Disease extent was E2 in 48% and E3 in 52%, including three patients with an ileoanal pouch. Baseline disease activity was moderate, with a median partial Mayo score of 4±2. MRK was prescribed as monotherapy in 77%; 33% received co-induction (24% corticosteroids, 11% apheresis), and 39.4% underwent extended induction. At week 12, 56.5% achieved symptomatic remission and 86.9% a clinical response. At week 24 (n = 10), 70% were in clinical remission and 90% had a clinical response. Median faecal calprotectin fell from 2964 µg/g at baseline to 983 µg/g at week 12 and 586 µg/g at week 24 (p 0.001), with biochemical remission rates of 28.6% and 31.2%, respectively. Two patients developed pruritus: one mild, self-limiting case with successful re-challenge after negative allergy testing, and one confirmed delayed allergy. Overall, 81.8% of patients remained on treatment at last follow-up, while six patients (18.2%) discontinued MRK (four due to treatment failure, one by patient choice and one because of an adverse event). Median follow-up under MRK was 24 weeks (mean 29.9; range 4–71). Conclusion In this real-world cohort of long-standing, highly pre-treated UC, mirikizumab achieved high rates of PRO2-defined clinical response and remission, with a favourable short-term safety profile and high treatment persistence. Conflict of interest: Dr. Elosua Gonzalez, Alfonso: I have served as a speaker, consultant, or advisory board member, and has received educational support from AbbVie, Johnson & Johnson, Adacyte, Takeda, Faes Farma, Ferring, and Tillotts Pharma.** Zabalza, Lucía: LZ has received financial support to attend courses and congresses from AbbVie, Adacyte, Johnson & Johnson, Takeda, Ferring, Faes Farma, and Cassen. Vicuña, Miren: No conflict of interest Rubio, Saioa: No conflict of interest Nantes Castillejo, Oscar: ON has served as speaker, consultant or research or education funding from MSD, Abbvie, Pfizer, Takeda, Janssen, Ferring, Shire Pharmaceuticals, Dr. Falk Pharma, Tillotts Pharma, Faes-Farma, Adacyte therapeutics and Sanofi-Aventis. Rodriguez, Cristina: CR has received scientific advice, support for research and/or educational activities, research grants, and has participated in consultancy services from Abbvie, Adacyte, MSD, Janssen, Pfizer, Tillots, Ferring, Falk, Takeda, Lilly, and Galapagos
Gonzalez et al. (Thu,) studied this question.