Purpose

The primary objectives of the study by study part are: Part A: To determine the treatment effect of dupilumab compared with placebo in adult and adolescent patients with EoE after 24 weeks of treatment as assessed by histological and clinical measures and to inform/confirm the final sample size determination for Part B. Part B: To demonstrate the efficacy of dupilumab treatment compared with placebo in adult and adolescent patients with EoE after 24 weeks of treatment as assessed by histological and clinical measures. Part C: To assess the safety and efficacy of dupilumab treatment in adult and adolescent patients with EoE after up to 52 weeks of treatment as assessed by histological and clinical measures. The secondary objectives of the study are: * To evaluate the safety, tolerability, and immunogenicity of dupilumab treatment for up to 52 weeks in adult and adolescent patients with EoE * To explore the relationship between dupilumab concentration and responses in adult and adolescent patients with EoE, using descriptive analyses * To evaluate the effects of dupilumab on transcriptomic signatures associated with EoE and type 2 inflammation * To demonstrate the efficacy of dupilumab treatment compared to placebo after 24 weeks and 52 weeks of treatment in adult and adolescent patients with EoE who have previously received swallowed topical corticosteroids