Efficacy and Safety of Vonoprazan Compared to Lansoprazole in Participants With Erosive Esophagitis

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 capable of understanding and complying with protocol requirements.
• The participant signs and dates a written, informed consent form and any required privacy authorization prior to the initiation of any study procedures. The participant is informed of the full nature and purpose of the study, including possible risks and side-effects. The participant has the ability to cooperate with the investigator. Ample time and opportunity should be given to read and understand verbal and/or written instructions.
• The participant is found to have endoscopically confirmed EE of LA Classification Grades A to D during the Screening Period (Visit 1) as assessed by a central adjudicator. The target number of participants with LA classification Grade C or D will be approximately 30% of the total number of participants (300 total). Enrollment of EE participants with Grade A or B will end when the number of participants with Grade A or B EE is approximately 700 or 70% of the total planned number of participants. Given the invasive nature of an endoscopy, any endoscopic confirmation performed in a routine clinical setting before signing the informed consent will be acceptable to use for the purpose of fulfilling the screening requirement if all of the following apply: (1) appropriate endoscopy pictures were taken; (2) appropriate gastric biopsy samples were taken; (3) the endoscopy pictures can be sent to the central adjudicator via the adjudication systems; and (4) all screening procedures (including the completion of adjudication) AND randomization can be completed within a 7-day period after the date of the endoscopy.
• A female participant of childbearing potential who is or may be sexually active with a nonsterilized male partner agrees to routinely use adequate contraception from the signing of informed consent until 4 weeks after the last dose of study drug.

Exclusion Criteria

• The participant's endoscopic examination for entering this study fails to confirm EE within 7 days (no later than 10 days on rare occasion with sponsor approval) prior to randomization.
• The participant is determined to be positive for Helicobacter pylori (HP) or has had an HP infection within 45 days of randomization.
• The participant has endoscopic Barrett's esophagus (>1 cm of columnar-lined esophagus) and/or definite dysplastic changes in the esophagus.
• The participant has any other condition affecting the esophagus, including eosinophilic esophagitis; esophageal varices; viral or fungal infection; esophageal stricture; a history of radiation therapy, radiofrequency ablation, endoscopic mucosal resection, or cryotherapy to the esophagus; or any history of caustic or physiochemical trauma (including sclerotherapy or esophageal variceal band ligation). However, participants diagnosed with Schatzki's ring (mucosal tissue ring around lower esophageal sphincter) are eligible to participate.
• The participant has scleroderma (systemic sclerosis).
• The participant has a history of surgery or endoscopic treatment affecting gastroesophageal reflux, including fundoplication and dilation for esophageal stricture (except Schatzki's ring) or a history of gastric or duodenal surgery (except endoscopic removal of benign polyps).
• The participant has an active gastric or duodenal ulcer at the start of the Screening Period. Additionally, participants with gastric or duodenal erosions are permitted to participate.
• The participant has received any investigational compound (including those in post marketing studies) within 30 days prior to the start of the Screening Period. A participant who has been screen failed from another clinical study and who has not been dosed may be considered for enrollment in this study.
• The participant is a study site employee, an immediate family mem