Real-world effectiveness and predictors of need for extended induction of mirikizumab therapy in ulcerative colitis.

Background: Mirikizumab (MIR), a selective interleukin-23p19 inhibitor, has demonstrated efficacy in randomized trials for moderate-to-severe ulcerative colitis (UC). Real-world data remain limited. Here, we evaluated the effectiveness, durability, and safety of MIR in routine clinical practice. Methods: We conducted a retrospective, multicentre cohort study of adults with UC initiating MIR at two tertiary centres in Canada. Clinical, biomarker, endoscopic, and safety outcomes were assessed at weeks 12, 28, and 52. The primary outcome was corticosteroid-free (CSF) clinical remission at week 12. Secondary outcomes included CSF clinical remission at weeks 28 and 52, CSF clinical response, mucosal healing, treatment persistence, extended induction, and serious adverse events. Predictors of extended induction were evaluated using logistic regression. Results: Eighty-two patients were included; 94% were previously exposed to at least one advanced therapy. CSF clinical remission was achieved in 24% of patients at week 12, 35% at weeks 28, and 33% at week 52, with corresponding CSF clinical response rates of 45%, 53%, and 40%. Moreover, 40% of the cohort received extended induction. In the extended induction subgroup, CSF clinical remission was observed in 19% at week 28 and 22% at week 52, with CSF clinical response rates observed in 37% and 30%, respectively. Early CSF clinical response at week 12 was associated with treatment persistence. The incidence of serious adverse events was low, with no new safety signals. Conclusions: In this multicentre real-world Canadian cohort of predominantly treatment-experienced patients with UC, MIR demonstrated clinically relevant effectiveness, acceptable durability, and a favourable safety profile over 1 year.