Vedolizumab dalspiegels na subcutane toediening bij patiënten met inflammatoire darmziekten

Background: A new subcutaneous (SC) formulation of vedolizumab (VDZ) has become available for the treatment of inflammatory bowel diseases (IBD) since April 2020. An exposure-response relationship has been described for intravenous (IV) VDZ. However, little is known about VDZ serum levels during SC treatment. Objective and design: In this observational cohort study, we aimed to assess trough levels during SC VDZ therapy in IBD patients. Secondary, we analysed predictors for VDZ trough levels and examined the relationship between VDZ trough levels and disease activity. Methods: IBD patients initiating SC VDZ treatment were included in our nationwide, real-world Initiative on Crohn and Colitis (ICC) registry. The primary outcome was the VDZ trough level. Secondary, we assessed predictors for VDZ levels using linear regression analysis and performed Receiver Operating Characteristic (ROC) analysis to determine concentration thresholds for prediction of corticosteroid free clinical remission at week 12. Results: We included 56 patients, 24 with Crohn's disease (CD) and 32 with ulcerative colitis (UC). 44 patients were switched from VDZ IV to SC and 12 VDZ naïve patients started with VDZ SC after induction with VDZ IV. Mean VDZ trough levels were 34.4 mg/L (standard deviation 12.9) after 13 weeks (interquartile range 11-20) of SC therapy. Mean VDZ levels increased statistically significantly from 20.5 mg/L to 35.2 mg/L (P < 0.001) for patients switching from IV to SC. Biochemical remission at baseline, higher VDZ levels during IV therapy and VDZ measurement by liquid chromato-graphy-tandem mass spectrometry (LC-MS/MS) were associated with higher VDZ levels during SC therapy. Active smoking and prior use of > 1 biologic or tofaci-tinib were associated with lower VDZ levels during SC therapy. A VDZ level of ≥ 34.5 mg/L at week 13 was 60.0% sensitive, 75.0% specific with a 85.7% positive predictive value and 42.9% negative predictive value for corticosteroid free clinical remission at week 13. Conclusion: Mean VDZ trough levels during SC therapy were 34.4 mg/L. VDZ levels were statistically significant higher during SC therapy than during IV therapy.