To investigate the effect of multiple dosing, a further 3 cohorts (Cohorts 9-11), each comprising 12 participants were to be introduced to the protocol following completion of the single rising dose study. A final cohort, Cohort 12, consisting of 24 Western participants and 24 Japanese participants was to be used to assess the effect of TAK-438 and esomeprazole on the safety, tolerability, pharmacokinetics and pH of the stomach between these 2 ethnic groups.