A Study to Evaluate Vonoprazan in Children Who Have Symptomatic Gastroesophageal Reflux Disease

Inclusion Criteria:

1. The participant has a body weight within the 5th through 95th percentile by age,inclusive, as determined by the National Center for Health Statistics.

2. The participant must have a diagnosis of GERD prior to randomization and medicalhistory of signs or symptoms of GERD for at least 3 months prior to screening, basedon physical examination, current symptoms (eg, heartburn), or diagnostic tests (eg,pH or endoscopy). Notes in the medical records and/or other source documents, suchas prior endoscopies, can be used to support the diagnosis and will be recorded inthe electronic case report form (eCRF).

3. The participant has at least one moderate GERD symptom based on the GERD SymptomAssessment Investigator scale performed at screening.

4. The participant must be able to swallow study drug tablet with water.

5. Parent or legal guardian (ie, legally authorized representative [LAR]) is willingand able to complete the informed consent process and participants are able tocomply with study procedures and visit schedule.

6. Female participants who have experienced menarche must have a negative pregnancytest and will be counseled on pregnancy avoidance.

Exclusion Criteria:

1. The participant has used prescription or non-prescription proton pump inhibitors (PPIs) or histamine-2 receptor antagonist (H2RAs) within 7 days prior torandomization or requires use during the Treatment Period.

2. The participant has used sucralfate, or antacids within 1 day prior to randomizationor requires their use during the Treatment Period.

3. The participant has received other agents affecting digestive organs, includingmuscarinic antagonists (eg, hyoscyamine), prokinetics, oral anticholinergic agents,prostaglandins, bismuth from 30 days prior to Day 1 or requires their use during thecourse of the study.

4. The participant has received atazanavir sulfate or rilpivirine hydrochloride from 5days prior to Day 1 or requires their use during the course of the study.

5. The participant has received any investigational compound (including vonoprazan)within 30 days prior to the start of the Screening Period.

6. The participant is an immediate family member or is in a dependent relationship witha study site employee who is involved in the conduct of this study (eg, child,sibling) or participant may have consented under duress.

7. The participant requires hospitalization or has surgery scheduled during the courseof the study or has undergone major surgical procedures within 30 days prior to theScreening Period.

8. The participant has undergone prior gastrointestinal surgeries.

9. The participant has any abnormal laboratory test values that are consideredclinically significant in the opinion of the investigator during the ScreeningPeriod.

10. The participant has a history of hypersensitivity or allergies to vonoprazan (including the formulation excipients: D-mannitol, microcrystalline cellulose,hydroxypropylcellulose, fumaric acid, ascorbic acid, croscarmellose sodium,magnesium stearate, hypromellose, macrogol 8000, and titanium dioxide, or red oryellow ferric oxide).

11. The participant has used any prescription or over-the-counter medications (includingherbal or nutritional supplements), other than those already excluded in criteria 1to 5 above, within 14 days before the first dose of study drug or throughout thestudy. That is, unless the medication(s) is permitted by the sponsor following areview of available data which confirms concomitant administration of the medicationis unlikely to affect either the safety of the participant or the pharmacokineticsof vonoprazan.

12. The participant has consumed grapefruit or grapefruit juice, Seville orange orSeville orange-containing products (eg, marmalade), or other food products that maybe CYP3A4 inhibitors (eg, vegetables from the mustard green family [kale, broccoli,watercress, collard greens, kohlrabi, Brussels sprouts, mustard] and charbroiledmeats) within 7 days (or 5 half-lives) before the first dose of study drug orthroughout the study.

13. The participant has positive results at screening for human immunodeficiency virus,hepatitis B virus, or hepatitis C virus (HCV).

14. The participant has severe renal impairment (estimated glomerular filtration rate < 30 mL/min).

15. The participant has moderate to severe hepatic impairment (Child-Pugh Class B andChild-Pugh Class C).

16. The participant has any of the following abnormal laboratory test values at thestart of the Screening Period:

17. Creatinine levels: >0.8 mg/dL (>70 μmol/L).

18. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >2 × theupper limit of normal (ULN) or total bilirubin >2 × ULN (except participantswith Gilbert Syndrome).

19. In the opinion of the investigator, the participant is not suitable for entry intothe study.