A prospective cohort study to assess the relevance of vedolizumab drug level monitoring in IBD patients.

Background: Vedolizumab (VDZ) drug monitoring strategies in inflammatory bowel disease (IBD) patients have not been systematically investigated so far. We evaluated the correlation between VDZ trough levels (VTL) and the treatment response in IBD. Methods: Fifty-one patients with active IBD on or starting a therapy with VDZ were enrolled in this prospective and observational single centre study. Disease activity indices, blood tests, and anthropometric parameters were assessed over a time period of 6 months. One hundred and fifty-five VDZ serum trough levels were measured directly before the next scheduled application using liquid chromatography mass spectrometry (LC-MS/MS). Results: VDZ treatment was found to be clinically effective (Harvey Bradshaw Index (HBI) dropping from 10 to 5.5 points (p < .0005) in Crohn’s disease (CD) patients; partial Mayo score (pMS) from 4.4 to 2.1 points (p < .0005) in ulcerative colitis patients (UC). CRP levels tended to decrease and haemoglobin levels to increase under VDZ therapy. CD patients with a serum CRP level lower than 5 mg/l exhibited significantly higher VTL than those with elevated CRP levels (34.9 versus 21.7 µg/ml, p = .00153). UC patients with haemoglobin levels higher 12 g/dl at the time of VTL measurement had significantly higher VTL compared to patients with lower haemoglobin levels (35.4 versus 15.6 µg/ml, p < .0005). Conclusions: Our data suggest a significant correlation between VTL and response to therapy in IBD patients (higher VTL associated with better response). [ABSTRACT FROM AUTHOR]