SummaryBackgroundCT‐P13, a biosimilar of the reference product infliximab, has been approved for the treatment of ulcerative colitis on the basis of the results of trials conducted in patients with spondyloarthritis and rheumatoid arthritis.AimTo compare the effectiveness and safety of CT‐P13 and the reference product in infliximab‐naive patients with ulcerative colitisMethodsA comparative real‐life equivalence cohort study was conducted using the French nationwide health administrative database. Infliximab‐naive patients with ulcerative colitis over 15 years of age who started infliximab with no other indications for infliximab were included. The primary outcome was a composite endpoint (death, ulcerative colitis‐related surgery, all‐cause hospitalisation and reimbursement for other biologics). Equivalence was defined as a 95% CI of the hazard ratio (HR) of CT‐P13 vs the reference product, in a multivariable marginal Cox model situated within prespecified margins of (0.80‐1.25).ResultsA total of 3112 patients were included between 1 January 2015 and 30 June 2017: 1434 received the reference product, 1678 received CT‐P13. Overall, 710 patients in the reference product group and 743 patients in the CT‐P13 group met the composite endpoint. In multivariable analysis of the primary outcome, CT‐P13 was equivalent to the reference product (HR 1.04; 95% CI: 0.94‐1.15). The number of serious infections was lower in the CT‐P13 group (HR 0.65; 95% CI: 0.48‐0.88). There was no difference in the incidence of solid or haematologic malignancy (HR 0.81; 95% CI: 0.41‐1.60).ConclusionsThe effectiveness of CT‐P13 is equivalent and the risk of serious infections could be lower than that of the reference product for infliximab‐naive patients with ulcerative colitis.