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

Phase 2

Completed

Brief Summary: 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.

Recruitment & Eligibility

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

Arm && Interventions

Group	Intervention	Description
Placebo	Placebo	Participants will receive a film-coated placebo tablet matching gefapixant BID for 28 days.
Gefapixant 45 mg	Gefapixant 45 mg	Participants will receive a gefapixant 45 mg film-coated tablet BID for 28 days.

Primary Outcome Measures

Name	Time	Method
Number of Participants Who Experienced an Adverse Event	Up to 6 weeks	An adverse event is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment.
Number of Participants Who Discontinued Study Treatment Due to an Adverse Event	Up to 4 weeks	An adverse event is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment.

Secondary Outcome Measures

Name	Time	Method
Change From Baseline at Week 4 in Log-transformed 24-hour Coughs Per Hour	Baseline and Week 4	Cough frequency will be evaluated using a digital recording device which records sounds from the lungs and trachea through a chest contact sensor, as well as ambient sounds through a lapel microphone. Change from baseline in log-transformed 24-hour coughs per hour = log (24-hour coughs per hour at post-baseline) - log (24-hour coughs per hour at baseline). The denominators may be different if the recording period is actually \<24 hours but ≥20 hours).
Change From Baseline at Week 4 in Log-transformed Awake Coughs Per Hour	Baseline and Week 4	Change from baseline at Week 4 in awake coughs per hour is the average hourly cough frequency (based on sound recordings) during the 24-hour monitoring period while the participant is awake. Change from baseline in log-transformed awake coughs per hour = log (awake coughs per hour at post-baseline) - log (awake coughs per hour at baseline) for the monitoring period the participant is awake.

Locations (16): Yokohama City Minato Red Cross Hospital ( Site 3306)
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Yokohama, Kanagawa, Japan
Tsumura Cardiovascular-internal-medicine Clinic ( Site 3314)
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Kakogawa, Hyogo, Japan
Saiseikai Kanazawa Hospital ( Site 3337)
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Kanazawa, Ishikawa, Japan
Nagaoka Red Cross Hospital ( Site 3307)
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Nagaoka, Niigata, Japan
Idaimae Minamiyojo Int Clinic ( Site 3321)
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Sapporo, Hokkaido, Japan
Matsusaka City Hospital ( Site 3325)
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Matsusaka, Mie, Japan
Kawaguchi Respiratory Clinic ( Site 3304)
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Higashiosaka, Osaka, Japan
Nagoya City University Hospital ( Site 3328)
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Nagoya, Aichi, Japan
Hitachi, Ltd. Hitachinaka General Hospital ( Site 3301)
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Hitachinaka, Ibaraki, Japan
Komatsu Municipal Hospital ( Site 3308)
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Komatsu, Ishikawa, Japan
Kamei Internal Medicine and Respiratory Clinic ( Site 3309)
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Takamatsu, Kagawa, Japan
Fukushima Medical University Hospital ( Site 3338)
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Fukushima, Japan
Doujin Memorial Medical Foundation, Meiwa Hospital ( Site 3310)
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Tokyo, Japan
Nihonbashi Medical & Allergy Clinic ( Site 3334)
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Tokyo, Japan
Showa University Hospital ( Site 3331)
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Tokyo, Japan
Fukuwa Clinic ( Site 3311)
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Tokyo, Japan