Study to Determine the Efficacy and Safety of Dupilumab in Adult and Adolescent Patients With Eosinophilic Esophagitis (EoE)

Key Inclusion Criteria (Parts A \& B):

* A documented diagnosis of EoE by endoscopic biopsy
* Baseline endoscopic biopsies with a demonstration on central reading of intraepithelial eosinophilic infiltration
* History (by patient report) of an average of at least 2 episodes of dysphagia (with intake of solids) per week in the 4 weeks prior to screening

Key Exclusion Criteria (Parts A \& B):

* Body weight ≤40 kg
* Prior participation in a dupilumab clinical trial, or past or current treatment with dupilumab
* Initiation or change of a food-elimination diet regimen or re-introduction of a previously eliminated food group in the 6 weeks prior to screening.
* Other causes of esophageal eosinophilia or the following conditions: hypereosinophilic syndrome and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)
* Active Helicobacter pylori infection
* History of achalasia, Crohn's disease, ulcerative colitis, celiac disease, and prior esophageal surgery
* Any esophageal stricture unable to be passed with a standard, diagnostic, 9 to10 mm upper endoscope or any critical esophageal stricture that requires dilation at screening
* History of bleeding disorders or esophageal varices
* Pregnant or breastfeeding women, or women planning to become pregnant or breastfeed during the study

Key Exclusion Criteria (Part C):

* Participants who, during Part A or Part B, developed a serious adverse event (SAE) and/or adverse event (AE) deemed related to study drug, which in the opinion of the investigator could indicate that continued treatment with study drug may present an unreasonable risk for the participant
* Participants who became pregnant during Part A or Part B
* Participants who are prematurely discontinued from study drug due to an AE (patients who are prematurely discontinued from study drug due to lack of efficacy are eligible to enter Part C)
* Patients who did not undergo endoscopy with biopsies prior to receiving rescue treatment

Note: Other inclusion/ exclusion criteria apply