Evidence to Support Monitoring of Vedolizumab Trough Concentrations in Patients With Inflammatory Bowel Diseases

Background & Aims Trough concentrations of vedolizumab were found to correlate with clinical response in phase 3 studies of patients with ulcerative colitis (UC) or Crohn's disease (CD). Nevertheless, there are no solid data to support monitoring of vedolizumab trough concentrations in treated patients. We investigated the correlation between vedolizumab exposure and response in a real-world population and aimed to identify patient factors that affect exposure and response. Methods We performed a retrospective cohort study of 179 consecutive patients (66 with UC and 113 with CD) who began vedolizumab therapy from September 1, 2015, through October 1, 2016, at University Hospitals Leuven, Belgium. Serum concentrations of vedolizumab were measured before all infusions up to week 30. Effectiveness endpoints included endoscopic healing (UC, Mayo endoscopic sub-score ≤1; CD, absence of ulcers), clinical response (physicians' global assessment), and biologic response or remission (based on level of C-reactive protein) and were assessed at week 14 (for patients with UC) and week 22 (for patients with CD). A stepwise forward addition-backward elimination modeling approach was performed to identify factors independently associated with vedolizumab exposure and response. Results Vedolizumab trough concentrations >30.0 μg/mL at week 2, >24.0 μg/mL at week 6, and >14.0 μg/mL during maintenance therapy associated with a higher probability of attaining the effectiveness endpoints for patients with UC or CD ( P P Conclusions In a retrospective study of 179 patients with CD or UC, we observed a correlation between vedolizumab exposure and response. These findings support monitoring of vedolizumab trough concentrations to predict patients' outcome.