An Antibody Against IL-5 Reduces Numbers of Esophageal Intraepithelial Eosinophils in Children With Eosinophilic Esophagitis

Background & Aims The role of interleukin (IL)-5 in the pathogenesis of eosinophilic esophagitis (EoE) has been established in animal models; anti–IL-5 therapy has been reported to be effective in adults. We investigated whether IL-5 has a role in accumulation of esophageal eosinophils in children with EoE and whether therapy with mepolizumab, an antibody against IL-5, reduces the number of esophageal intraepithelial eosinophils in children with EoE. Methods We performed an international, multicenter, double-blind, randomized, prospective study of 59 children with EoE, defined as baseline peak count of esophageal intraepithelial eosinophils of ≥20 in at least 1 high-power field (hpf). Patients received an infusion every 4 weeks (a total of 3 infusions) of 0.55, 2.5, or 10 mg/kg mepolizumab. No placebo group was used. Results Baseline peak and mean esophageal intraepithelial eosinophil counts were (mean ± SE) 122.5 ± 8.78 and 39.1 ± 3.63 per hpf, respectively. Four weeks after the third infusion, peak eosinophil counts were