This is a multicenter, open-label, randomized, parallel-group study to exploratorily evaluate the effect on gastric mucosal tissue and the safety of long-term administration of vonoprazan in maintenance treatment after healed EE, and the curative effect of vonoprazan versus lansoprazole in participants with EE.~Participants endoscopically diagnosed with EE of Los Angeles (LA) Classification Grades A to D at the start of treatment (Week 0 of the healing phase) will be randomly assigned to receive either vonoprazan 20 mg or lansoprazole 30 mg to be taken once daily for up to 8 weeks. Subjects with healed EE as confirmed endoscopically at Week 4 or 8 in the healing phase will enter the maintenance phase.~In the maintenance phase, the vonoprazan group and the lansoprazole group will be administered a starting dose of 10 mg and 15 mg, respectively, once daily up to 260 weeks.~If the principal investigator or investigator judged the effect of vonoprazan 10 mg or lansoprazole 15 mg to be insufficient as the maintenance treatment of EE, vonoprazan and lansoprazole may be increased to 20 mg and 30 mg, respectively.~The research period will consist of two subperiods: healing phase in which participants with EE will receive treatment (for 4 or 8 weeks) and maintenance phase in which participants will receive maintenance treatment (for 260 weeks), and thus, a total of up to 268 weeks. The number of visits will be a maximum of 18 visits. Planned number of research subjects, as the number of research subjects for entry to the maintenance phase, will be 130 participants in the vonoprazan group and 65 participants in the lansoprazole group.
The purpose of this study is exploratorily evaluate the effect on gastric mucosal tissue and the safety of long-term administration (260 weeks: 5 years) of vonoprazan 10 mg or 20 mg in patients receiving maintenance treatment after healed erosive esophagitis (EE), and the curative effect of vonoprazan 20 mg versus lansoprazole in patients with EE.