Higher Trough Vedolizumab Concentrations during Maintenance Therapy are Associated with Corticosteroid-Free Remission in Inflammatory Bowel Disease

Background and Aims: Vedolizumab is an anti-α4β7 biologic approved for ulcerative colitis [UC] and Crohn's disease [CD]. We aimed to examine the association of maintenance vedolizumab concentrations with remission. Methods: We performed a cross-sectional multi-centre study of inflammatory bowel disease [IBD] patients on maintenance vedolizumab. A homogeneous mobility shift assay [HMSA] was used to determine trough serum concentrations of vedolizumab and anti-drug antibodies [ATVs]. The primary outcome was corticosteroid-free clinical and biochemical remission defined as a composite of clinical remission, normalized C-reactive protein [CRP] and no corticosteroid use in 4 weeks. Secondary outcomes included corticosteroid-free endoscopic and deep remission. Vedolizumab concentrations were compared between patients in remission and with active disease. Logistic regression, adjusting for confounders, assessed the association between concentrations and remission. Results: In total, 258 IBD patients were included [55% CD and 45% UC]. Patients in clinical and biochemical remission had significantly higher vedolizumab concentrations [12.7 μg/mL vs 10.1 μg/mL, p = 0.002]. Concentrations were also higher among patients in endoscopic and deep remission [14.2 μg/mL vs 8.5 μg/mL, p = 0.003 and 14.8 μg/mL vs 10.1 μg/mL, p = 0.01, respectively]. After controlling for potential confounders, IBD patients with vedolizumab concentrations >11.5 μg/mL were nearly 2.4 times more likely to be in corticosteroid-free clinical and biochemical remission. Only 1.6% of patients had ATVs. Conclusions: In a large real-world cohort of vedolizumab maintenance concentrations, IBD patients with remission defined by objective measures [CRP and endoscopy] had significantly higher trough vedolizumab concentrations and immunogenicity was uncommon.