Connecting the Dots Between Pharmacokinetics, Inflammatory Biomarkers, and Mucosal Healing in Patients on Infliximab with Inflammatory Bowel Disease

Background/Objectives: Mucosal healing (MH) is a key therapeutic target in inflammatory bowel disease (IBD) associated with sustained remission, reduced hospitalisation, and improved outcomes. Its assessment relies on endoscopic evaluation, which is invasive, costly, and not always feasible. Therapeutic drug monitoring (TDM) of infliximab (IFX) and evaluation of available biomarkers may provide non-invasive tools for predicting treatment response. This study investigated the association between IFX pharmacokinetics, routinely available blood biomarkers and MH to identify potential surrogates for predicting treatment outcomes. Methods: A monocentric, retrospective, real-world study was conducted, and pharmacokinetic analysis was performed in NONMEM version 7.5, applying a model with priors to estimate individual pharmacokinetic parameters. Endoscopic findings were collected, and patients were categorised according to achievement of MH. Univariate and multivariable logistic regression analyses were performed to evaluate the predictive value of tested variables, and receiver operating characteristic (ROC) curve analysis was performed to assess discriminative performance. Results: All evaluated variables demonstrated statistically significant associations with MH (p < 0.05). IFX clearance showed a strong inverse relationship with the probability of achieving MH. Leukocyte count exhibited particularly good discriminative ability, with an area under the ROC curve of 74.04% and an odds ratio of 0.78, highlighting its potential clinical utility. Multivariable logistic regression identified a model including IFX clearance and platelet count (PLT) as the most promising predictors of MH. Significant differences between patient subgroups indicated the association of higher PLT and modestly increased IFX clearance with a lower probability of MH. Conclusions: IFX clearance represents a promising surrogate marker for MH. TDM-derived parameters coupled with routinely available biomarkers may improve treatment response assessment. Combining pharmacokinetic and biomarker-based approaches could reduce reliance on repeated endoscopies while facilitating more effective IBD monitoring in clinical practice.