The study population for each of Cohorts 1 to 7 consisted of 9 subjects; with 6 subjects randomized to receive a single dose of TAK-438, and 3 subjects to receive placebo. Subjects in Cohorts 1 to 7 received a single dose of study drug after a 10-hour fast. The starting dose was 1 mg followed by administrations of 5, 10, 20, 15, 40, and 30 mg.