Summary 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 μg/mL (interquartile range, IQR 21.2‐33.8 μg/mL) at week 2, 23 μg/mL (IQR 15‐34.5 μg/mL) at week 6 and 10.7 μg/mL (IQR 4.6‐20.4 μg/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 μg/mL, P = 0.035). A cut‐off trough level of 18 μg/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 μg/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.

No abstract