A Study to Assess the Safety and Efficacy of Oral Etrasimod in Adult Participants With Eosinophilic Esophagitis

Inclusion Criteria: * Have an eosinophilic esophagitis (EoE) diagnosis prior to screening and histologically active disease with an esophageal peak eosinophil count (PEC) of ≥ 15 eosinophils per high powered field (eos/hpf) * Have dysphagia, defined as solid food going down slowly or getting stuck in the throat with an average frequency of ≥ 2 episodes per week over 2 weeks during the Screening period Inclusion Criteria for the Extension Treatment Period * Completion of the Week 24 study visit \[including esophagogastroduodenoscopy (EGD)\] * Compliance with study procedures during the Double-Blind Treatment Period as assessed by the Investigator * No notable safety concerns during the Double-Blind Treatment Period, as determined by the Investigator * Willing to comply with all study visits and procedures for the Extension Treatment Period Exclusion Criteria: * History of any of the non-EoE conditions or procedures that may interfere with the evaluation of or affect the histologic (eg eosinophilic gastritis), endoscopic (eg, high-grade esophageal stenosis), or symptom endpoints (eg, esophageal resection) of the study * Undergone dilation of an esophageal stricture within 12 weeks prior to Screening EGD * Use of corticosteroids for the treatment of EoE within 8 weeks prior to Screening EGD * Discontinue, initiate, or change dosing (dosage/frequency) of the following therapies for EoE within 8 weeks prior to Screening EGD. Participants on any of the following therapy need to stay on a stable regimen during study participation: 1. Elemental diet 2. EoE food trigger elimination diet 3. Proton pump inhibitor (PPI) therapy * Used any immunotherapy/desensitization including oral immunotherapy (OIT) or sublingual immunotherapy (SLIT) within 12 months prior to the Screening EGD. Note: Stable (ie, ≥ 6 months prior to the Screening EGD) subcutaneous immunotherapy (SCIT) is permitted. Participants on SCIT need to stay on a stable treatment during study participation * Used any protocol-specified immunomodulatory therapies within the protocol-specified timeframe prior to Baseline (eg, dupilumab, benralizumab, omalizumab, or infliximab within 12 weeks; a sphingosine-1-phosphate receptor modulator at any time) * Use of any investigational agent or device within 12 weeks prior to Baseline * Females who are pregnant