The purpose of this study is to evaluate the efficacy and safety of gefapixant in participants with recent onset chronic cough (duration >8 weeks after onset of cough symptoms) for <12 months and a diagnosis of refractory or unexplained chronic cough. The primary hypothesis is that gefapixant is superior to placebo in improving cough-related quality of life measured as change from baseline in the Leicester Cough Questionnaire (LCQ) total score at Week 12.



Eligible Ages
Over 18 Years
Eligible Genders
Accepts Healthy Volunteers

Inclusion Criteria

  • Chest radiograph or computerized topography (CT) scan of the thorax performed after the onset of cough symptoms but before the diagnosis of chronic cough require consultation with the Sponsor to determine if acceptable for inclusion in study - Has chronic cough (defined as duration of >8 weeks after onset of cough symptoms) for <12 months prior to the screening visit (<14 months after onset of cough symptoms) - Has a diagnosis of refractory chronic cough or unexplained chronic cough - Female participants are not pregnant, not breastfeeding, not of childbearing potential, or agree to follow contraceptive guidance

Exclusion Criteria

  • Is a current smoker - Has given up smoking within 12 months of screening - Is a former smoker with a smoking history greater than 20 pack-years (1 pack of 20 cigarettes per day for 20 years) - Has a history of respiratory tract infection or recent change in pulmonary status within 4 weeks of screening - Has a history of chronic bronchitis, defined as cough that produces >1 tablespoon of phlegm, that occurs every day for at least 3 months in a row - Has a history of malignancy ≤5 years prior to signing informed consent except for adequately treated basal cell or squamous cell skin cancer or cervical cancer - Is a user of recreational or illicit drugs or a recent history (within the last year) of drug or alcohol abuse - Has a history of anaphylaxis or cutaneous adverse drug reaction to sulfonamide-containing drugs - Has a known allergy to gefapixant or its excipients - Has donated or lost ≥1 unit (~300 mL) of blood within 8 weeks prior to first dose of gefapixant - Has previously received gefapixant - Is currently participating or has participated in an interventional clinical study within 30 days of participating in this current study

Study Design

Phase 3
Study Type
Intervention Model
Parallel Assignment
Primary Purpose
Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)

Arm Groups

ArmDescriptionAssigned Intervention
Participants will receive gefapixant at a dose of 45 mg administered as an oral tablet twice daily for 12 weeks.
  • Drug: Gefapixant
    Administered twice daily as an oral tablet of 45 mg
    Other names:
    • MK-7264
Placebo Comparator
Participants will receive placebo matching gefapixant, administered as an oral tablet twice daily for 12 weeks.
  • Drug: Placebo
    Administered twice daily as a placebo oral tablet matching gefapixant

Recruiting Locations

More Details

Merck Sharp & Dohme Corp.

Study Contact

Toll Free Number


Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.