Therapeutic Monitoring of Adalimumab at Non-Trough Levels to Gauge Its Efficacy in Patients with Inflammatory Bowel Disease in Clinical Practice

Abstract Background: Adalimumab (ADA) trough level and anti-ADA antibody (AAA) positivity could influence mucosal healing and loss of response in patients with inflammatory bowel disease (IBD). This study aimed to clarify the correlation between ADA monitoring, including non-trough level and real-world IBD clinical outcomes.Methods: This retrospective, observational, single-center study included 19 patients with ulcerative colitis (UC) and 33 patients with Crohn’s disease (CD) treated with ADA from January 2007 to August 2018. Serum ADA and AAA levels were measured 4‒14 days after ADA administration.Results: The AAA positivity rate was 23.1% (12/52). The ADA continuity was higher in the AAA-negative group than in the AAA-positive group (P = 0.223). Receiver operating characteristic (ROC) analysis revealed that a serum AAA cut-off value of 9.2 µg/mL was associated with ADA continuity (area under the curve [AUC]: 0.767, 95% confidence interval [CI]: 0.636–0.899). The ADA level was significantly higher in the endoscopic remission group than in the non-remission group (12.4 vs. 6.4 µg/mL, P = 0.02). Based on the ROC curve analysis results of serum ADA level and endoscopic remission, the cut-off value of serum ADA level was set to 11.1 µg/mL (AUC: 0.716, 95% CI: 0.533–0.900).Conclusions: Regardless of infliximab administration history, under combined use of ADA with immunomodulators and AAA positivity, ADA continuity was significantly higher when the serum AAA level 4–14 days after ADA administration was ≥9.2 µg/mL. Furthermore, endoscopic remission can be expected with a serum ADA level of ≥11.1 µg/mL.