Phase 3 Study of TAK-438 10 mg in the Treatment of Non-Erosive Gastroesophageal Reflux Disease (NERD)

Inclusion Criteria

• In the opinion of the investigator, the participant is capable of understanding and complying with protocol requirements.
• The participant signs and dates a written informed consent form prior to the initiation of any study procedures.
• The participant with NERD.
• The participant is endoscopically confirmed to have the modified Los Angeles (LA) Classification Grade N or M at the start of the run-in period (Visit 1).

To allow efficacy evaluation in the participants with Grade N as well as in those with Grade M, the target number of participants in each grade is at least 30% of the total number of participants. Enrollment of patients with either Grade N or M will end when the number of enrolled participants with each grade exceeds 332, or 70% of the total planned number of participants.

• The participant experiences recurrent heartburn, on at least 2 days a week over the last 3 weeks prior to the start of the run-in period (Visit 1).
• The participant is either a male or female outpatient with a minimum age of 20 years at the time of informed consent signing. However, participants who are hospitalized only for examination purposes are also allowed to participate.
• A female participant of childbearing potential agrees to use routinely adequate contraception from signing of informed consent throughout the duration of the study, and for 4 weeks after the last dose of study drug.
• The participant's compliance to the study drug has been good (75% or better) in the run-in period.
• The participant has experienced heartburn on at least 2 days in the last 1 week prior to randomization.
• The participant has appropriately provided in the patient's diary all the required information during the run-in period.

Exclusion Criteria

• The participant has received any investigational compound within 84 days prior to the first dose of study drug.
• The participant has received TAK-438 in a previous clinical study or as a therapeutic agent, except one with experience of receiving TAK-438 as an adjunct therapy for H. pylori eradication, who can be enrolled in this study.
• The participant is an immediate family member, study site employee, or is in a dependent relationship with a study site employee who is involved in conduct of this study (eg, spouse, parent, child, sibling) or may consent under duress.
• The participant has donated at least 400 mL of blood within the 90 days prior to the start of the run-in period (Visit 1).
• Endoscopic examination for entering this study fails to diagnose NERD within 84 days before the start of the run-in period (Visit 1).
• The participant has any complications affecting the esophagus, including Barrett's esophagus (3 cm or more, long segment Barrett's esophagus [LSBE]), eosinophilic esophagitis, esophageal varices, scleroderma, viral or fungal infection, and esophageal stenosis; a history of radiation therapy or cryotherapy for the esophagus; or caustic or physiochemical trauma (eg, esophageal sclerotherapy). However, participants with Barrett's mucosa (less than 3 cm, short segment Barrett's esophagus [SSBE]) or Schatzki's ring (a mucosal tissue ring lining the inferior esophageal sphincter) are permitted to participate.
• The participant has a history of surgery or treatment affecting gastroesophageal reflux, including fundoplication and mechanical dilatation for esophageal stenosis (except Schatzki's ring), or a history of gastric or duodenal surgery (except endoscopic removal of benign polyps).
• The participant has acute upper gastrointestinal bleeding or gastric or duodenal ulcer, characterized by a defective mucosa with white coating, within 30 days prior to the start of the run-in period (Visit 1). However, participants with gastric or duodenal erosion are permitted to participate.
• The participant has acute gastritis or acute exacerbation of chronic gastritis.
• The participant has, or has a history of, Zollinger-Ellison syndrome or gastric acid