摘要Background Data on biosimilar use in pediatric inflammatory bowel diseases(IBD)are scarce compared to the status of studies in adults,resulting in limitations in its treatment.We compared effectiveness and safety of biosimilars versus origi-nators in this population.Methods We used data from the French National Health Data System to identify children(less than 18 years old at treatment initiation)initiating treatment with a biosimilar or the originator infliximab or adalimumab for Crohn's disease(CD)or ulcera-tive colitis(UC),from first biosimilar launch(January 2015 and October 2018,respectively)to 31 December 2022.Patients'follow-up went until 30 June 2023.We compared the risks of treatment failure and overnight hospitalization in biosimilar versus originator new users using inverse harzard ratio(HR)of probability of treatment weighted Cox regressions(IPTW).Results We included 5870 patients(infliximab:n=3491;adalimumab:n=2379)in the study.Biosimilars represented,respectively,76.0％(n=2652)and 29.0％(n=691)of infliximab and adalimumab initiations.CD represented 70.9％(n=2476)and 69.0％(n=1642)of infliximab and adalimumab initiations.Biosimilar use was not associated with increased risks of treatment failure[IPTW HR(95％confidence interval,CI):infliximab 0.92(0.78-1.09)in CD,0.98(0.76-1.27)in UC;adalimumab 0.98(0.85-1.14)in CD,1.01(0.82-1.24)in UC].Occurrence of all-cause hospitalization was not different between exposure groups[IPTW HR(95％CI):infliximab 0.96(0.78-1.18);adalimumab 1.03(0.80-1.33)].No difference in occurrence of serious infections,mainly gastro-intestinal or dermatological,was found.Conclusion We provide reassuring results on the use,effectiveness and safety of biosimilars in a large unselected pediatric population suffering from IBD.