Background: In randomised controlled trials, mirikizumab achieved clinical remission and improved outcomes of patients with moderate to severe ulcerative colitis (UC). However, there is currently no real-world evidence for mirikizumab.

Objective: To evaluate the real-world effectiveness and safety of mirikizumab.

Methods: In a retrospective cohort study among three facilities, we included patients with UC who first received mirikizumab between June 2023 and April 2024. The primary outcome was the change in the partial Mayo score (PMS) from week 0 to 12. Secondary outcomes included changes in serum C-reactive protein (CRP) and leucine-rich α2-glycoprotein (LRG) levels from week 0 to 12; clinical remission rate (PMS < 2 with rectal bleeding subscore of 0), CRP remission rate (< 3.0 mg/L), and LRG remission rate (< 12.7 μg/mL) at week 12; and adverse events during induction therapy.

Results: We included 52 patients. Median (interquartile range) PMS decreased from week 0 to 12 (5 [3-6] to 2 [0-3], p < 0.001). CRP and LRG levels also decreased (CRP: 3.8 [0.9-7.3] to 1.8 [0.5-4.0] mg/L, p = 0.015; LRG: 20.1 [16.3-23.2] to 15.9 [12.8-23.2] μg/mL, p = 0.014). Rates of clinical remission, CRP remission, and LRG remission at week 12 were 44.2%, 67.3%, and 27.3%, respectively. There were no adverse events leading to permanent discontinuation of mirikizumab or death.

Conclusions: This real-world study demonstrated the short-term effectiveness and safety of mirikizumab in patients with UC.