A Study in Adult Participants With EoE to Evaluate Vonoprazan 20 mg Compared to Placebo After 12 Weeks and to Evaluate Vonoprazan 20 mg Up to 24 Weeks

Inclusion Criteria:

• The participant is ≥18 years of age at the time of informed consent signing.

• In the opinion of the investigator or subinvestigators, the participant is capableof understanding and complying with protocol requirements, including completion andcompliance with the electronic diary. The diary must be completed on at least 11 ofthe last 14 days in the 2 weeks prior to Visit 2 (Day -1).

• The participant signs and dates a written informed consent form (ICF) and anyrequired privacy authorization prior to the initiation of any study procedures.

• The participant has a peak eosinophil count of at least 15 eos/hpf [X 400] from atleast 2 of the 3 esophageal levels on screening endoscopy as measured in at least 6biopsies, at least 2 each from the proximal, mid, and distal segments of theesophagus based on central reading.

• The participant has 4 or more days with dysphagia episodes documented via electronicdiary in the 2 weeks prior to Visit 2 (Day -1).

• The participant must remain on a stable diet for at least 6 weeks prior to theScreening Period and is expected to remain on a stable diet during the course of thestudy; stable diet is defined as not initiating new elimination diets orreintroducing previously eliminated foods.

• A female participant of childbearing potential who is or may be sexually active witha non-sterilized male partner agrees to routinely use adequate contraception fromthe signing of informed consent until 4 weeks after the last dose of study drug.

Exclusion Criteria:

• The participant is on a pure liquid diet.

• The participant has documented erosive esophagitis at the screening endoscopy.

• The participant has other known causes of esophageal eosinophilia or either of thefollowing conditions: hypereosinophilic syndrome, or eosinophilic granulomatosiswith polyangiitis (Churg-Strauss Syndrome).

• The participant has a documented diagnosis of eosinophilic gastritis, duodenitis,jejunitis, ileitis, proctitis, or colitis.

• The participant has endoscopic Barrett's esophagus (>1 cm of columnar-linedesophagus) or dysplastic changes in the esophagus.

• The participant has a history of achalasia, Crohn's disease, ulcerative colitis, orceliac disease.

• The participant has a known active Helicobacter pylori infection.

• The participant has any other clinically significant structural conditions affectingthe esophagus, including: esophageal varices, viral or fungal infection, and historyof radiation therapy, radiofrequency ablation, endoscopic mucosal resection,cryotherapy to the esophagus, caustic or physiochemical trauma (includingsclerotherapy or esophageal variceal band ligation), or esophageal surgery.

• The participant has a history of surgery or non-EoE endoscopic intervention, such asgastric bypass, fundoplication, gastric sleeve, or a history of gastric or duodenalsurgery (except endoscopic removal of benign polyps).

• The participant has gastric ulcer(s) or duodenal ulcer(s) within 4 weeks before thefirst dose of study drug.

• The participant has had clinically significant upper or lower gastrointestinalbleeding within 4 weeks prior to the Screening Period.

• The participant has esophageal stricture(s) unable to be passed with an 8 to 10 mmendoscope, clinically requires dilation, or has a history of dilation within the 3months prior to the Screening Period.

• Use of prescription or non-prescription PPIs or PCABs within 2 months prior to theScreening Period.

• Use of swallowed topical corticosteroid or budesonide oral suspension for EoE within 2 months prior to the Screening Period.

• Use of systemic corticosteroid for any condition within 3 months prior to theScreening Period.

• Use of inhaled or nasal glucocorticoids within 3 months prior to the ScreeningPeriod, except stable dose for at least 3 months prior to the Screening Period forany condition (should not be changed during the study).

• Use of dupilumab within 3 months prior to the Screening Period.

• The participant has received any investigational compound within 30 days or anyinvestigational biologic within 3 months prior to the start of the Screening Period (including those in post-marketing studies) or vonoprazan in a clinical trial at anytime. A participant who has been screen failed from another clinical study and whohas not been dosed may be considered for enrollment in this study.

• The participant has used immunomodulatory therapy within 3 months prior to theScreening Period or anticipates using immunomodulatory therapy during the study (except for any ongoing regimen of allergy therapy).

• The participant is a study site employee, an immediate family member, is in adependent relationship with a study site employee who is involved in the conduct ofthis study (eg, spouse, parent, child, sibling), or who may have consented underduress.

• The participant has a history of hypersensitivity or allergies to vonoprazan (including the formulation excipients: D-mannitol, microcrystalline cellulose,hydroxypropyl cellulose, ascorbic acid, fumaric acid, croscarmellose sodium,magnesium stearate, hypromellose, macrogol 8000, titanium oxide, or red ferricoxide). Skin testing may be performed according to local standard practice toconfirm hypersensitivity.

• The participant has a history of alcohol abuse, illegal drug use, drug addiction orregularly consumes alcohol within the 12 months prior to the Screening Period (basedon self-report). Participants must have a negative urine drug screen fornon-prescribed medications at screening. Participants taking prescription drugs willbe allowed. Occasional, recreational use of cannabis is allowed. However,participants with a cannabis use disorder (eg, frequent use, functional-socialimpairment, withdrawal symptoms) per the opinion of the investigator should beexcluded.

• The participant is taking any excluded medications or treatments listed in theprotocol.

• If female, the participant is pregnant, lactating, or intending to become pregnantbefore, during, or within 4 weeks after participating in this study, or intending todonate ova during such time period.

• The participant has a history or clinical manifestations of significant centralnervous system, cardiovascular, pulmonary, metabolic, other gastrointestinal,urological, endocrine, or hematological disease that, in the opinion of theinvestigator, would confound the study results or compromise participant safety.

• The participant has a history of malignancy (including MALToma) or has been treatedfor malignancy within 5 years prior to the start of the Screening Period (Visit 1).The participant may be included in the study if he/she has recovered from cutaneousbasal cell carcinoma or cervical carcinoma in situ.

• The participant has acquired immunodeficiency syndrome or human immunodeficiencyvirus infection, or tests positive for the hepatitis B surface antigen, hepatitis Cvirus (HCV) antibody, or HCV-ribonucleic acid (RNA). However, participants who testpositive for HCV antibody but negative for HCV-RNA are permitted to participate.

• The participant has Zollinger-Ellison syndrome or other gastric acid hypersecretoryconditions.

• The participant requires hospitalization or has surgery scheduled during the courseof the study or has undergone major surgical procedures within 30 days prior to theScreening Period.

• The participant has moderate to severe hepatic impairment (Child-Pugh Class B andChild-Pugh Class C).

• The participant has severe renal impairment (estimated glomerular filtration rate <30 mL/min).

• The participant has any of the following abnormal laboratory test values at thestart of the Screening Period:

1. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >2 × theupper limit of normal (ULN) or total bilirubin >2 × ULN (except participantswith Gilbert Syndrome).

2. Creatinine levels: >2 mg/dL (>177 μmol/L)

• The participant is refractory to prior PPI therapy as judged by the investigator.