Maarten Cozijnsen

23 Chapter 1 General introduction Biosimilars Biosimilars of IFX have become available on the European market since the expiration of the patent of the IFX originator. The similarity of IFX biosimilar CT-P13 with IFX originator was extensively tested. First in pre-clinical tests that compared their physicochemical characteristics, and by comparing their biological activities in several models related to their mechanisms of action. Afterwards, their similarity was confirmed clinically in two of the indications of IFX: ankylosing spondylitis and rheumatoid arthritis. 76,77 Based on these results, CT-P13 received market approval for all IFX’s indications, including pediatric CD. Only recently, the results of a randomized, double-blind, non-inferiority trial were published comparing the efficacy and safety of continuing on IFX originator with switching to CT-P13 in patients with various diseases including CD on stable treatment with IFX originator. 78 A total of 482 patients (155 CD patients [32%]) with stable conditions under IFX treatment, were randomized to continue on IFX originator or switch to CT-P13. After 1 year follow-up, they reported similar rates of disease worsening (IFX originator vs CT-P13: 26% vs 30%) and similar rates of adverse events (AE: 70% vs 68%, SAE: 10% vs 9%). Notably, the study was not powered to show non-inferiority in CD specifically, but in the overall population. Additionally, multiple observational trials assessed the effects of switching from IFX originator to CT-P13, and these were recently combined in a systematic review. 79 The authors combined the data from 11 observational trials and 1007 IBD patients, and compared these results—i.e. efficacy, safety and immunogenicity rates of CT-P13—with the results of IFX originator as reported in preciously published trials. Again, they reported no significant differences. Currently, only one observational trial assessed the effect of switching to CT-P13 in pediatric CD. 80 A total of 32 pediatric CD patients—and 7 UC—were switched from IFX originator to CT-P13. The authors report that switching seemed to be safe and did not impact efficacy. Thus, the early results confirm the expected similarity of IFX originator and CT-P13 in CD. Yet studies on both long-term outcome and switching from the originator to the biosimilar in pediatric CD are still required.