Lower adalimumab trough levels are associated with higher bowel wall thickness in Crohn's disease

Background In Crohn's disease, higher adalimumab trough levels and negative anti-adalimumab-antibodies associate with better clinical and endoscopic outcomes. Intestinal ultrasound has become a relevant non-invasive method to monitor treatment. However, data on the association between adalimumab levels and bowel wall thickness measured with ultrasound is limited. Objective The purpose of this study was to examine the possible association between the sonographic transmural-thickness and adalimumab trough levels. Methods This prospective observational cohort study was conducted at Sheba Medical Center in 2014-2018. Crohn's disease patients on adalimumab maintenance therapy with intestinal ultrasound performed within <30 days of trough level measurement were included. Associations between terminal ileum and colonic thickness, adalimumab levels and therapy retention were assessed. Results Fifty events of ultrasound with concomitant adalimumab trough level measurements in 44 Crohn's disease patients were included. Patients with trough level <3 mu g/ml had significantly higher bowel wall thickness, both for terminal ileum (p = 0.04) and colon (p = 0.02). Thirty-two patients continued adalimumab therapy over one year. The adalimumab retention rate was higher among those with terminal ileum thickness <4 mm (p = 0.03). Conclusion Lower adalimumab trough levels were associated with higher bowel wall thickness indicating poorer therapy outcome. Transmural thickness measurement with ultrasound may be a useful target for guiding biologic therapy in Crohn's disease.