Abstract Background Inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn’s disease (CD), requires sustained control of gastrointestinal inflammation to improve patient outcomes. Vedolizumab (VDZ), a monoclonal antibody, has been approved for the induction and maintenance of remission in moderate to severe UC and CD. However, interpatient variability in VDZ pharmacokinetics (PK) complicates therapeutic drug monitoring (TDM). This study aimed to assess whether VDZ clearance (CL) could serve as a surrogate marker for remission, outperforming trough concentrations as a predictor. Methods This retrospective cohort study analysed 106 patients (61 UC and 45 CD) receiving 300 mg VDZ therapy at variable intervals (4, 6, or 8 weeks) after standard induction. Blood samples were collected at trough times, and VDZ concentrations were measured using ELISA. A population PK model was developed using NONMEM (version 7.5) to estimate VDZ CL. Statistical analyses included Fisher’s exact, t-test, and logistic regression to evaluate clinical predictors, while ROC curve analysis identified optimal cut-offs for clinical and endoscopic outcomes. Results A two-compartment model best described the PK of VDZ. The estimated CL was 0.159 L/day, increasing by 26.4% in patients previously treated with anti-TNF agents. Higher CL values correlated with thrombocytosis (Plt > 350·10^3/µL, AUROC = 76.9, 95% CI 62.8–91.1) and were significantly associated with reduced likelihood of remission. VDZ trough levels did not predict remission outcomes as effectively as CL, suggesting that AUC-based exposure metrics may better indicate clinical response. Conclusion This study demonstrates that VDZ CL, influenced by prior anti-TNF exposure and inflammatory markers, is a more reliable predictor of clinical and endoscopic remission than trough concentration. These findings support the integration of CL-based TDM for VDZ to optimize therapeutic outcomes in IBD management. Further research on AUC-based metrics may provide enhanced TDM guidance.
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