Background: Vedolizumab drug monitoring strategies in IBD patients have not been investigated systematically so far. Our aim was to evaluate the correlation between vedolizumab trough levels (VTL) and the treatment response in patients with IBD.
Methods: 51 adult patients with therapy-refractory chronic active ulcerative colitis (UC) (n=23), Crohn's disease (CD) (n=27) or indeterminate colitis (IC) (n=1) on or starting a therapy with vedolizumab were enrolled in this prospective single center study. Disease activity indices (Harvey-Bradshaw-Index, partial Mayo score), total blood count, albumine, ferritin, C-reactive protein (CRP), and anthropometric parameters were assessed. Over a time period of 6 months 155 vedolizumab serum trough levels were assessed directly before the next scheduled application using liquid chromatography mass spectrometry (LC-MS/MS).
Results: Vedolizumab treatment was found to be clinically effective in most of the enrolled patients as documented by a significant drop of the mean Harvey Bradshaw Index from 10 to 5.5 points (p<0.0005) in CD patients (n=27) and a significant decrease of the partial Mayo score from 4.4 to 2.1 points (p<0.0005) in UC patients (n=23). CRP level tended to decrease and hemoglobin levels to increase under vedolizumab therapy. We did not find a significant effect of the concomitant medication (prednisolone, azathioprine, and methotrexate) on VTL. We detected significantly higher VTL in patients with application of vedolizumab every 4 weeks than those receiving vedolizumab every 8 weeks (30.2 versus 17.2 μg/ml, p=0.005). 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=0.00153). UC patients with hemoglobin levels higher 12 g/dl at the time of VTL measurement had significantly higher VTL compared to patients with lower hemoglobin levels (35.4 versus 15.6 μg/ml, p<0.0005). Statistical analyses (receiver operating characteristics) indicate a significant association between VTL and treatment efficacy measured by CRP level in CD and hemoglobin level in UC.
Conclusions: Our data suggest a significant correlation between VTL and clinical response in IBD patients treated with vedolizumab, where patients with high VTL have a higher chance to reach the treatment goal than those with low VTL.