P674 Potential utility of therapeutic drug monitoring of adalimumab in predicting short-term mucosal healing and histologic remission in paediatric Crohn's disease patients

Abstract

Background: There is limited data regarding mucosal healing (MH) and therapeutic drug levels in paediatric Crohn's disease (CD) patients under adalimumab (ADL) treatment. We aimed to investigate the association between ADL trough levels (TLs) and MH, and between ADL TLs and histologic remission (HR) at 4 months from ADL treatment in the paediatric population of CD. Method(s): This study was a preliminary analysis of an ongoing prospective cohort in paediatric CD patients receiving ADL at the Department of Pediatrics, Samsung Medical Center. Moderate-to-severe luminal CD patients who were naive to biologics and receiving ADL before 19 years-old were included. Ileocolonoscopy and biopsies as well as clinical activity assessment, laboratory exams, including tests for ADL TLs and antibody to adalimumab (ATA) were performed at 4 months from adalimumab initiation. MH was defined as a Simple Endoscopic Score for Crohn's disease (SES-CD) of 0. His-tologic remission (HR) was defined as the complete absence of mi-croscopic inflammation on biopsy specimens obtained from sites of previous and current ulcerations. Adalimumab TLs were compared according to MH status at 4 months. Result(s): [Table Presented] Seventeen subjects were included in this study. At 4 months from ADL initiation, 14 (82.4%) were under clinical remission, 8 (47.1%) had achieved MH, and 4 patients (23.5%) had achieved HR. Dose intensification by interval shortening to every week was done in 1 patient (5.9%). ADL TLs were significantly higher in patients who achieved MH compared to those who did not (13.0+/-6.5 xg/mL vs. 6.2+/-2.6 xg/mL, p=0.023), and also significantly higher in patients who achieved HR compared to those who did not (17.9+/-5.3 xg/mL vs. 6.8+/-2.5 xg/mL, p=0.02). ATA was detected in 1 patient (5.9%). According to receiver operator characteristic (ROC) curve analysis, the optimal cut-point for predicting MH was 8.76 xg/mL. [Table Presented] Conclusion(s): Serum ADL TLs at 4 months were significantly higher in paediatric CD patients under MH or HR, compared to those who failed to achieve each outcome. Future relevant large-scale studies may guide in predicting short-term MH and HR in the era of treat-to-target.