P553 The safety and efficacy of adalimumab 80mg weekly as maintenance therapy in pediatric Crohn’s Disease

Abstract Background Intensification of adalimumab (ADL) dosing to weekly 40 mg injections, in response to low drug levels, has been shown to provide beneficial outcomes in pediatric patients with Crohn’s disease (CD). Our study aimed to evaluate the safety and efficacy of weekly 80 mg ADL administration in children with CD. Methods In this retrospective cohort study conducted across five Israeli centers, we reviewed the medical records of pediatric CD patients who received a high dose of ADL 80 mg weekly injections between 2016 and 2023. Collected data included demographic characteristics, disease features, laboratory studies, and treatment outcomes. Results Thirty-two children with CD were included: mean age 15.8 (±1.7) years at intensification, 21 male (66%), 18 (56%) with L3 phenotype. The median time to ADL 80 mg intensification from ADL induction was 48.4 weeks (IQR 23.1-122.5). The mean weighted Pediatric Crohn's Disease Activity Index (wPCDAI) was 28.5 (±16.9) at the time of intensification and the median calprotectin and C-reactive protein levels were 937 μg/g (IQR 540-1410) and 1.3 mg/dL (IQR 0.6-5.2), respectively. Clinically active disease was the main reason for ADL intensification (30, 94%). Baseline ADL levels were available in 30 patients (94%) with a median of 3.8 μg/mL (IQR 2.4-7.2). Among these, 23 children (77%) failed to achieve a target of ≥ 7.5 μg/mL. The median follow-up duration from the intensification dose was 91.2 weeks (IQR 53.6-149.1). Corticosteroids were required in 5/32 (15.6%) children, with a median time of 32.3 weeks (IQR 10.7-51.3) from intensification. There was no statistically significant difference in steroid utilization rates between children who achieved a target baseline drug level of ≥ 7.5 μg/mL and those who did not (p=0.934). Thirteen individuals (41%) discontinued ADL treatment, within a median of 24.7 weeks (IQR 11.7-57.1) from intensification. CD-related exacerbation, hospitalization, and surgery rates were 9 (28%), 4 (13%), and 2 (6%), respectively. No statistically significant differences were found in exacerbation (p=0.406), hospitalization (p=0.322), or surgery rates (p=0.427) between children who achieved a baseline ADL trough concentration level of ≥ 7.5 μg/mL and those who did not. Overall, ADL intensification was safe, but 3 (9%) patients developed new-onset psoriasis. Conclusion Our findings support the safety and efficacy of administering ADL at a weekly dosage of 80 mg as maintenance therapy in pe