Conditions: Refractory Chronic Cough
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 50
Healthy volunteers: yes

Brief summary:
The primary objective of this double-blind crossover study is to assess the effect of single doses of 50 mg and 300 mg gefapixant (AF-219/MK-7264) on cough reflex sensitivity to capsaicin in both healthy participants and participants with chronic cough. This study will also assess the effect of single doses of gefapixant on cough reflex sensitivity to adenosine triphosphate (ATP) in healthy participants and participants with chronic cough.

Detailed description:
Up to 30 participants (male and female) who meet all entry criteria will be randomly assigned to treatment with gefapixant or matching placebo.

There will be a Screening Period, a Baseline Visit (cough participants only), and four Treatment Periods, with a washout period between treatments. Participants will return after their last Treatment Visit for a Follow-up Visit.

At the Screening Visit and during the Treatment Periods, cough sensitivity will be measured by standard clinical methodology incorporating two cough challenges: 1) capsaicin; 2) ATP. The ATP challenge will only be performed during the study treatment period. The Baseline Visit (cough participants only) will occur prior to Treatment Period 1. Daytime cough monitoring will be performed at the Baseline Visit and during each of the four Treatment Periods (cough participants only).

Arms:
arm 1: Gefapixant 50 mg (1 tablet) administered as a single dose arm 2: Gefapixant 300 mg (6 tablets) administered as a single dose arm 3: Placebo-matching tablets administered as a single dose

Interventions: intervention 1: Gefapixant intervention 2: Placebo
Intervention descriptions: intervention 1: Gefapixant tablets administered orally as a single dose of 50 mg (1 tablet) or 300 mg (6 tablets) intervention 2: None

Protocol document: