The relationship among vedolizumab drug concentrations, biomarkers of inflammation, and clinical outcomes in a Canadian real-world study.

Background And Aims: Therapeutic drug monitoring is used to optimize anti-tumour necrosis factor biologic effectiveness in inflammatory bowel disease, but its role with other biological classes is unclear. This study explores relationships between post-induction vedolizumab trough concentrations and biochemical outcomes in a real-world study of individuals with inflammatory bowel disease.

Methods: This retrospective analysis of data from a national patient support program between 2018 and 2020, included 436 individuals with Crohn's disease or ulcerative colitis receiving vedolizumab. Optimal vedolizumab concentration thresholds (at weeks 6 and 14) were determined based on their ability to predict biochemical normalization (week 30 faecal calprotectin [<250 µg/g], C-reactive protein [<5 mg/l]). Thresholds best associated with each outcome were evaluated in multivariate analyses.

Results: Among patients with Crohn's disease, week 6 serum vedolizumab concentrations (>41.65 µg/ml) predicted normalization defined by C-reactive protein: Spearman correlation coefficient [] = -0.26, = 0.002 and multivariate analysis (MVA)-OR: 3.22, 95% CI: 1.32-7.87, = 0.01, and at week 14 (>22.25 µg/ml): = -0.38, < 0.0001, and MVA-OR: 3.21, 95% CI: 1.26-8.17 but not faecal calprotectin. Similarly, among patients with ulcerative colitis, week 6 vedolizumab concentrations (>39.65 g/ml) predicted normalization defined by C-reactive protein: = -0.26, = 0.005 and MVA-OR: 4.03, 95% CI: 1.30-12.52, = 0.016, and at week 14 (>17.35 µg/ml): = -0.39, = 0.0001 and MVA-OR: 6.95, 95% CI: 1.81-26.77, = 0.005, but not faecal calprotectin.

Conclusions: Induction and post-induction serum vedolizumab were not consistently associated with biochemical normalization. As such, proactive therapeutic drug monitoring for vedolizumab should not be routinely incorporated in a treat to target strategy for inflammatory bowel disease.

Clinical Trial Registration Number: NCT04567628.