Study of Gefapixant (MK-7264) in Adult Japanese Participants With Unexplained or Refractory Chronic Cough (MK-7264-033)

Phase II Study, Randomized, Double-Blind, Placebo-Controlled 4-Week Clinical Study, to Evaluate the Efficacy and Safety of MK-7264 in Adult Japanese Participants With Unexplained or Refractory Chronic Cough

This estimation study (no hypotheses) will evaluate the safety, tolerability, and efficacy of gefapixant (MK-7264) in Japanese adult participants with unexplained or refractory chronic cough.

Inclusion Criteria:

• Chest radiograph or computed tomography scan of the thorax (within 5 years of Screening/Visit 1 and after the onset of chronic cough) not demonstrating any abnormality considered to be significantly contributing to the chronic cough or any other clinically significant lung disease in the opinion of the principal investigator or the sub-investigator.
• Has had chronic cough for ≥ 1 year and a diagnosis of refractory chronic cough or unexplained chronic cough.
• For female participants, is a female who is not pregnant, not breastfeeding, not of childbearing potential, or agrees to follow contraceptive guidance
• Provides written informed consent and is willing and able to comply with the study protocol (including use of the digital cough recording device and completion of study questionnaires)

Exclusion Criteria:

• Is a current smoker or has given up smoking within 12 months of Screening, or is a former smoker with a pack-year history >20 pack-years
• Has a history of upper or lower respiratory tract infection or recent clinically significant change in pulmonary status
• Has a history of chronic bronchitis
• Is currently taking an angiotensin converting enzyme inhibitor (ACEI), or has used an ACEI within 3 months of Screening
• Has a history of malignancy ≤5 years
• Has a screening systolic blood pressure >160 millimeters of mercury (mmHg) or a diastolic blood pressure >90 mm Hg
• Has a history of cutaneous adverse drug reaction to sulfonamides with or without systemic symptoms or history of anaphylaxis to sulfonamides
• Is a user of recreational or illicit drugs or has had a recent history of drug or alcohol abuse or dependence
• Has a known allergy/sensitivity or contraindication to gefapixant
• Has donated or lost ≥1 unit of blood within 8 weeks prior to the first dose of gefapixant
• Has previously received gefapixant or is currently participating in or has participated in an interventional clinical study