Drug survival and immunogenicity after switching from remicade to biosimilar CT-P13 in inflammatory bowel disease patients: Two-year follow-up of a prospective observational cohort study

Background The infliximab biosimilar has entered daily inflammatory bowel disease (IBD) practice. However, real-life outcomes beyond 1 year after switching are scarce. We aimed to investigate the long-term drug survival, immunogenicity, and pharmacokinetics 2 years after switching to CT-P13 in IBD patients. Methods We performed a single-center prospective observational cohort study in all Remicade-treated IBD patients who previously switched to CT-P13. We systematically documented reasons for discontinuation, trough levels, and antidrug antibodies to infliximab (ADAs) at baseline, week 16, week 52, and week 104. Clinical and biochemical disease activity (HBI, SCCAI, CRP) and adverse events were registered. Results Eighty-three patients were enrolled, 57 had Crohn's disease, 24 had ulcerative colitis, and 2 were IBD-unclassified. At week 104, 55 of 83 (66%) patients remained on CT-P13, and 3 were lost to follow-up. Reasons for discontinuation were loss of response (n = 10), adverse events (n = 8), and disease remission (n = 7). ADAs were present in 5/83 patients at baseline (before switching), in 2 patients before week 52, and no subsequent ADAs were detected until week 104. Median trough levels and clinical and biochemical disease activity at baseline, week 16, week 52 and week 104 did not significantly change. Conclusion In a prospective cohort with >2-year follow-up, 66% of IBD patients continued CT-P13 after switching from Remicade. Two new cases with ADAs were observed in year 1, but subsequently no immunogenicity was detected. These results are reassuring and suggest that switching to CT-P13 does not impact long-term clinical outcomes.