A Study of Gefapixant (MK-7264) in Adult Participants With Chronic Cough (MK-7264-030)

This study will have a main 24-week treatment period and a 28-week extension period of
treatment.

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 at least 1 year with a diagnosis of refractory chronic cough
or unexplained chronic cough

- 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 greater than 20 pack-years

- Has a history of 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 an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m^2 at Screening OR
an eGFR ≥30 mL/min/1.73 m^2 and <50 mL/min/1.73 m^2 at Screening with unstable renal
function

- Has a history of malignancy <=5 years

- Is a user of recreational or illicit drugs or has had a recent history of drug or
alcohol abuse or dependence

- Has a history of anaphylaxis or cutaneous adverse drug reaction (with or without
systemic symptoms) to sulfonamide antibiotics or other sulfonamide-containing drugs

- 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