This study is designed to confirm the non-inferiority of Tegoprazan 25 mg, compared to Lansoprazole 15 mg, to prevent gastroduodenal ulcers and verify the safety of tegoprazan following oral administration of tegoprazan 25 mg QD or lansoprazole 15 mg QD in patients on long-term treatment with NSAIDs.

This is a double-blind, randomized, active-controlled, phase 3 study. Subjects will be randomly assigned to one of the two treatment groups (tegoprazan 25 mg, lansoprazole 15 mg).

Inclusion Criteria:

• ≥60 years of age, or ≥20 years of age with a history of gastroduodenal ulcers (gastric and/or duodenal ulcers) at screening
• Requires continued treatment with NSAIDs for ≥24 weeks

Exclusion Criteria:

• Has an active stage (A1, A2) or healing stage (H1, H2) of gastroduodenal ulcers per the Sakita-Miwa classification identified by upper GI endoscopy at screening
• Has uncontrolled severe hypertension
• Has severe heart failure, congestive heart failure (NYHA Ⅱ to Ⅳ), ischemic heart disease (unstable angina, myocardial infarction), or peripheral artery disease, or has undergone coronary artery bypass graft (CABG) who is considered ineligible for treatment with NSAIDs
• Has a positive H. pylori test at screening