Factors that influence infliximab biosimilar trough levels in the pediatric inflammatory bowel disease population

The pharmacokinetics and pharmacodynamics of biosimilar infliximab (IFX-BioS) in pediatric inflammatory bowel disease (IBD) are poorly investigated. The aim of this study was to investigate factors predicting IFX-BioS trough levels (TLs). IBD children with an indication to start IFX-BioS were included in this prospective observational study (January 2021-June 2022). TLs were measured at the 4^th and 6^th infusions and correlated with several covariates. A total of 110 TLs in 55 children were included. The multivariate linear regression model at the 4^th infusion found a positive correlation between TLs and age at diagnosis (B:1.950, 95% CI: [0.019, 3.882], <i>p</i> = 0.048) and IFX-BioS dose/kg (B:1.962, 95% CI: [0.238, 3.687], <i>p</i> = 0.029), and a negative correlation with clinical scores (B:-0.401, 95% CI: [−0.738, −0.064], <i>p</i> = 0.023). At the 6^th infusion, female gender (B:6.887, 95% CI: [0.861, 12.913], <i>p</i> = 0.029), hemoglobin (B:1.853, 95% CI: [0.501, 3.204], <i>p</i> = 0.011), and IFX-BioS dose/kg (B:1.792, 95% CI: [0.979, 2.605], <i>p</i> &lt; 0.001) were found to be positively correlated to TLs. No association between combined clinical and biochemical remission and TLs was found. This study discovered some predictors for IFX-BioS TLs in IBD children. Knowledge of predictive factors could help physicians choose the best dosing regimen.