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 [ρ] = −0.26, P = 0.002 and multivariate analysis (MVA)—OR: 3.22, 95% CI: 1.32–7.87, P = 0.01, and at week 14 (>22.25 µg/ml): ρ = −0.38, P < 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: ρ = −0.26, P = 0.005 and MVA—OR: 4.03, 95% CI: 1.30–12.52, P = 0.016, and at week 14 (>17.35 µg/ml): ρ = −0.39, P = 0.0001 and MVA—OR: 6.95, 95% CI: 1.81–26.77, P = 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.