S831 Long-Term Treatment With Dupilumab Maintains Histologic Improvements in Children With Eosinophilic Esophagitis (EoE): 100-Week Follow-Up Results From the EoE KIDS Study Open-Label Extension

Introduction: Eosinophilic esophagitis (EoE) is a chronic, progressive, type 2 inflammatory disease characterized by eosinophilic infiltration and other histopathologic abnormalities of the esophageal mucosa. Dupilumab is approved for EoE in the U.S. and E.U. in patients aged ≥1 year and weighing ≥15 kg. The phase 3 Study to Investigate the Efficacy and Safety of Dupilumab in Pediatric Patients With Active Eosinophilic Esophagitis (EoE KIDS) trial (NCT04394351) evaluated efficacy and safety of dupilumab vs placebo in pediatric patients with active EoE. Here, we examined histopathologic features of EoE after dupilumab treatment in the open-label extension period of EoE KIDS. Methods: In EoE KIDS, patients aged ≥1 year to <12 years were randomized to dupilumab or placebo for a 16-week double-blind period (Part A), switched to or continued active treatment for a 36-week extension (Part B), and then proceeded to an open-label extension (Part C) where all patients received the same weight-tiered dupilumab regimen. Esophageal biopsies were assessed for peak esophageal intraepithelial eosinophil count (PEC) and EoE Histologic Scoring System (EoEHSS) scores. The EoEHSS evaluates the severity (grade) and extent (stage) of 8 EoE features associated with inflammatory or architectural abnormalities; higher scores are associated with greater severity/extent of disease features. Results: Overall, 61 patients were enrolled in Part C; 33 patients who previously received the higher-exposure dose of dupilumab (similar to the FDA-approved dose in EoE) were included in the analysis. Proportions of patients achieving histologic remission (PEC ≤6 eosinophils/high-power field [eos/hpf]) with dupilumab were maintained up to week 100. At week 100 compared with week 52, numerically greater proportions of the Part C population achieved PEC of ≤1 (45.5% vs 39.4%) and <15 eos/hpf (90.9% vs 81.8%). Mean (95% confidence interval) changes from Part A baseline at week 100 were maintained vs week 52 in EoEHSS overall grade (-0.85 [CI -1.04 to -0.65] vs -0.87 [CI -1.01 to -0.73]) and stage scores (-0.87 [CI -1.04 to -0.70] vs -0.83 [CI -0.96 to -0.71]). Reductions in EoEHSS inflammatory and architectural grade/stage subscores were also maintained from week 52 to week 100. Conclusion: After 100 weeks of long-term treatment, dupilumab maintained or improved the proportions of pediatric patients with PEC ≤1, ≤6, and <15 eos/hpf relative to week 52. Long-term dupilumab also maintained improvements in the severity and extent of histopathologic features assessed by the EoEHSS.