Early vedolizumab trough levels predict mucosal healing in inflammatory bowel disease: a multicentre prospective observational study

Background: The correlation between vedolizumab trough levels during induction therapy and mucosal healing remains unknown. Aim: To compare early vedolizumab trough levels in patients with and without mucosal healing within the first year after treatment initiation. Methods: We prospectively collected vedolizumab trough levels in all inflammatory bowel disease patients at weeks 2, 6 and 14 of vedolizumab treatment in three French referral centres between 1 June 2014 and 31 March 2017. Results of every patient that underwent mucosal assessment by magnetic resonance imaging and/or endoscopy in the first year after treatment initiation were analysed. Results: Median vedolizumab trough levels in the overall population (n=82) were 27 mu g/mL (interquartile range, IQR 21.2-33.8 mu g/mL) at week 2, 23 mu g/mL (IQR 15-34.5 mu g/mL) at week 6 and 10.7 mu g/mL (IQR 4.6-20.4 mu g/mL) at week 14. Only median vedolizumab trough levels at week 6 differed between patients with and without mucosal healing within the first year after treatment initiation (26.8 vs 15.1 mu g/mL, P=0.035). A cut-off trough level of 18 mu g/mL at week 6 predicted mucosal healing within the first year after the start of vedolizumab with an area under the receiver operating curve of 0.735 (95% confidence interval 0.531-0.939). A vedolizumab trough level above 18 mu g/mL at week 6 was the only independent variable associated with mucosal healing within the first year of treatment (odds ratio 15.7, 95% confidence interval 2.4-173.0, P=0.01). Conclusion: Early therapeutic drug monitoring might improve timely detection of vedolizumab-treated patients in need for an intensified dosing regimen.