A Unblinded Study of TAK-438 (20 mg) for Prevention of Recurrence of Gastric or Duodenal Ulcer During Long-Term Non-Steroid Anti-Inflammatory Drug (NSAID) Therapy

Inclusion Criteria:

1. Participants who, in the opinion of the principal investigator or subinvestigator, arecapable of understanding the details of the study and complying with them.

2. Prior to study commencement, participants who are capable of signing and dating theinformation/consent form.

3. Participants with a chronic disease (rheumatoid arthritis, osteoarthritis, etc.) whichrequires continuous NSAID oral therapy for pain control during treatment period.

4. Participants who meet either 1 or 2 below according to gastric or duodenal endoscopy:

• Ulcer scar (defined, in this study, as regenerative mucosa, convergence ofmucosal fold, gastric wall transformation, etc) has been confirmed duringendoscopy on the study drug initiation day (Visit 2).

• Ulcer (mucosal defects of 3 mm or larger with white moss) or ulcer scar has beenendoscopically confirmed before the study drug initiation day (Visit 2).

5. Outpatient participants (inpatients for examinations are acceptable)

6. Women with child-bearing potential must agree to routinely take appropriatecontraceptive measures throughout treatment period, from giving consent to the studyuntil 4 weeks after the final dose

Exclusion Criteria:

1. Participants who received treatment with another study drug (including approved drugsunder post-marketing surveillance) within 84 days prior to commencement of screening

2. Participants who have previously received TAK-438 in a clinical study or as atreatment

3. Participants who are employees of institutions participating in this study and familymembers of such employees, participants in a dependent relationship with employees ofinstitutions involved in conduct of the study (e.g., spouse, parent, child, sibling),and participants who are under duress in giving their consent

4. Participants who have donated 400 mL or more of blood within 90 days prior to thecommencement of screening

5. Participants with a plan to change the type, dosage or administration of NSAID

6. Participants with ulcer (mucosal defects of 3 mm or larger with white moss) or activehemorrhage confirmed during gastric or duodenal endoscopy on the study drug initiationday (Visit 2)

7. Participants with small intestinal hemorrhage, large intestinal hemorrhage, orgastrointestinal hemorrhage of unknown cause

8. Participants with a history of surgery or scheduled surgery influencing gastric acidsecretion (resection of upper gastrointestinal tract or vagotomy etc)

9. Participants with a history or complication of Zollinger-Ellison syndrome, or othergastric acid hypersecretion disorders

10. Participants with a history or complication of aspirin asthma

11. Participants who have a history of hypersensitivity or allergy to TAK-438 (includingits excipients) or NSAIDs

12. Participants with current use of illicit drug or a history of drug abuse. and/oralcohol dependence within one year prior to the commencement of screening

13. Participants who require treatment with prohibited concomitant drugs or therapies (see 7.3)

14. Female participants who are pregnant or lactating; those who plan to become pregnantor donate ova during treatment period, from giving consent until 4 weeks after finaldose

15. Participants with serious central nervous system disorders, cardiovascular disease,pulmonary disease, hepatic disease, renal disease, metabolic disease, gastrointestinaldisorders, urinary disorders, endocrine disease, or blood dyscrasia

16. Participants who plan to undergo surgery requiring hospitalization or requires surgeryduring the study period.

17. Participants with a history of a malignancy (or treatment thereof) within 5 yearsprior to the commencement of screening; however, participants with completely curedbasal cell carcinoma of skin or carcinoma in situ of the cervix may be included in thestudy.

18. Participants with acquired immune deficiency syndrome (AIDS; including HIV carriers)or hepatitis (including viral hepatitis carriers [HBs antigen or HCV antibodypositive]); however, participants who are hepatitis C virus (HCV) antigen negative orHCV-RNA negative may be included in the study.

19. Participants who meet either of the following laboratory test values at the beginningof screening (Visit 1)

• Serum creatinine value: higher than 2 mg/dL

• Alanine transaminase (ALT) or aspartate aminotransferase (AST): higher than 2.5 ×the upper limit of normal

• Total bilirubin: higher than 2.0 × the upper limit of normal