A 12-Week Study in Participants With Refractory Chronic Cough (MK-7264-012)

A 12-Week Study to Assess the Efficacy and Safety of AF 219 in Subjects With Refractory Chronic Cough

This study is designed to evaluate the efficacy of three dose regimens of gefapixant ([MK-7264] 7.5 mg, 20 mg, and 50 mg) relative to placebo in reducing awake objective cough frequency. The primary hypothesis for this trial is that at least one dose regimen of gefapixant is superior to placebo with respect to the mean change from baseline in awake cough frequency (on the log scale).

Inclusion Criteria:

• Women and Men between 18 and 80 years of age inclusive
• Have refractory chronic cough
• Women of child-bearing potential must use 2 forms of acceptable birth control - Have provided written informed consent.
• Are willing and able to comply with all aspects of the protocol

Exclusion Criteria:

• Current smoker
• Forced Expiratory Volume in 1 second (FEV1)/Forced Vital Capacity (FVC) ratio <60%
• History of upper or lower respiratory tract infection or recent significant change in pulmonary status within 4 weeks of the Baseline Visit
• History of opioid use within 1 week of the Baseline Visit
• Body mass index (BMI) <18 kg/m^2 or ≥ 40 kg/m^2
• History of concurrent malignancy or recurrence of malignancy within 2 years prior to Screening (not including subjects with <3 excised basal cell carcinomas)
• Screening systolic blood pressure (SBP) >160 mm Hg or a diastolic blood pressure (DBP) >90 mm Hg
• Clinically significant abnormal electrocardiogram (ECG) at Screening
• Significantly abnormal laboratory tests at Screening
• Pregnant or Breastfeeding
• Other severe, acute, or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with trial participation or investigational product administration or may interfere with the interpretation of trial results and, in the judgment of the Investigator or Sponsor, would make the participant inappropriate for entry into this trial