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 intra-epithelial 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 <5 per hpf in 5 of 57 children (8.8%); we did not observe differences among groups given different doses of mepolizumab. Reduced peak and mean eosinophil counts, to <20 per hpf, were observed in 18 of 57 (31.6%) and 51 of 57 (89.5%) children, respectively. Peak and mean esophageal intraepithelial eosinophil counts decreased significantly to 40.2 +/- 5.17 and 9.3 +/- 1.25 per hpf, respectively (P < .0001). An analysis to evaluate predictors of response associated a higher mean baseline esophageal intraepithelial eosinophil count with a greater reduction in mean count (P < .0001). CONCLUSIONS: IL-5 is involved in the pathogenesis of EoE in children. Mepolizumab, an antibody against IL-5, reduces esophageal eosinophilic inflammation in these patients.