Ultrasound transmural healing correlates with higher adalimumab drug concentration in Crohn's disease only in the short-term.

Background: anti-TNF drugs have revolutionized the treatment of Crohn's disease (CD) and have set new therapeutic targets. A direct correlation between anti-TNF trough levels and endoscopic healing in inflammatory bowel disease (IBD) patients has been established, but the association between drug levels and transmural healing assessed by ultrasound is not yet clearly defined.

Aims: to evaluate the correlation between the serum concentration of adalimumab (ADA) and sonographic transmural healing in CD patients at different times during follow-up.

Methods: in this retrospective, cross-sectional study, all patients with CD who were undergoing treatment with ADA in our center were included. Intestinal ultrasound (IUS) was performed before the initiation of the drug and for response monitoring. ADA serum-trough levels were compared between patients with and without transmural healing at different periods of time.

Results: ninety-two patients were included, and all patients showed signs of inflammatory activity in the baseline IUS. During IUS monitoring of the response to ADA, 34 (34.8 %) patients presented transmural healing. Among patients in the first year of treatment, those with sonographic healing showed higher median levels than patients without transmural healing (12.0 µg/ml vs 9.3 µg/ml, respectively; p = 0.007). There was no correlation between ADA levels and sonographic healing in patients undergoing treatment for over a year.

Conclusions: higher ADA trough levels correlated with transmural healing with ultrasound during the first year of treatment. This correlation was not found after one year of treatment.