A Study to Learn How a Medicine That Reduces Stomach Acid Affects the Level of Sisunatovir in the Blood of Healthy Adults.

• Male and female participants aged 18 years or older (or the minimum age of consent in accordance with local regulations) at screening who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, blood pressure, pulse rate and standard 12-lead electrocardiogram (ECG).
• Body mass index (BMI) of 16-32 kg/m2; and a total body weight >45 kg

Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine,pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
• Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality or other conditions that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
• Previous administration with an investigational product (drug or vaccine) within 30 days (or as determined by the local requirement) or 5 half-lives preceding the first dose of study intervention used in this study (whichever is longer). Participation in studies of other investigational products (drug or vaccine) at any time during their participation in this study.
• A positive urine drug test at screening or admission.
• A positive serum pregnancy test at screening and/or positive urine/serum pregnancy test in woman/women of childbearing potential (WOCBP) at Day -1
• Current use of any prohibited concomitant medication(s) for sisunatovir and/or medication(s) that are contraindicated in the rabeprazole prescribing information.
• Use of tobacco/nicotine containing products
• Screening supine blood pressure (BP) ≥140 mm Hg (systolic) or ≥90 mm Hg (diastolic) for participants \<60 years; and ≥150/90 mm Hg for participants ≥60 years old, following at least 5 minutes of supine rest.
• Renal impairment as defined by an estimated glomerular filtration rate (eGFR) (units of mL/min/1.73m²) \<60 mL/min(/1.73m²) based on 2021 chronic kidney disease epidemiology (CKD-EPI).
• Standard 12-lead ECG that demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of study results
• Alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin (Bili) ≥ 1.05 × upper limit of normal (ULN). Participants with an elevated total bilirubin consistent with Gilbert's Disease should have a direct bilirubin measured and would be eligible for this study provided the direct bilirubin level is ≤ ULN.