Design and rationale of two phase 3 randomised controlled trials (COUGH-1 and COUGH-2) of gefapixant, a P2X3 receptor antagonist, in refractory or unexplained chronic cough

This paper describes the design, dose selection, and preliminary patient characteristics of two randomized, double-blind, parallel-group trials of gefapixant versus placebo in adult patients with refractory chronic cough or unexplained chronic cough. The primary endpoints are average 24-hour cough frequency; secondary endpoints are awake cough frequency, patient-reported outcomes, and responder analyses. Cough counts will be measured using the Vitalograph VitaloJAK cough monitor.