Phase 3 Trial of Gefapixant Shows Favorable Efficacy Results for Chronic Cough Treatment


The trials demonstrated a significant decrease in 24-hour coughs per hour versus placebo at 12 and 24 weeks.

Chronic cough

Merck recently announced the results from their ongoing phase 3 trials, which aimed to evaluate gefapixant, an investigational treatment for refractory or unexplained chronic cough.

The trials demonstrated a significant decrease in 24-hour coughs per hour versus placebo at 12 (COUGH-1) and 24 weeks (COUGH-2).

Gefapixant is currently an investigational treatment of refractory or unexplained chronic cough, which affects approximately 10% of the general adult population around the world. The treatment is a selective P2X3 receptor antagonist, taken orally. Chronic cough is believed to be caused by excessive activation of P2X3 receptors that promotes hyper-sensitization of sensory neurons. Neuronal hypersensitization in the airways and lung, which is triggered by an injury or infection, can cause an exaggerated, persistent, and frequent urge to cough.

There are currently no approved treatments for chronic cough, and up to 46% of cases have no identifiable cause despite thorough diagnostic investigation.

The studies – COUGH-1 and COUGH-2 – are international phase 3, randomized, double-blind, placebo-controlled trials that pursue evaluation of the efficacy and safety of gefapixant in alleviating cough frequency in adults with refractory or unexplained chronic cough. COUGH-1 utilized 732 participants, whereas COUGH-2 had 1317 participants, with defined patients according to guidelines from the American College of Chest Physicians (ACCP).

COUGH-1 and COUGH-2 both assigned participants to 1 of 3 groups: gefapixant 45 mg twice daily; gefapixant 15 mg twice daily; or placebo. The primary efficacy outcomes measure for both studies were 24-hour coughs per hour at week 12, and 24-hour coughs per hour at week 24. Secondary endpoints for both studies included awake coughs per hour. Coughs were measured using an ambulatory digital audio recording device.

Merck asserts that trials will continue in order to collect additional necessary safety data.

“The burden for patients faced with this disease underscores the need for effective therapeutic options for refractory and unexplained chronic cough,” said Dr. Roy Baynes, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories. “We are pleased gefapixant at the 45 mg dose met the primary efficacy endpoints in both phase 3 studies and we look forward to sharing the detailed findings at an upcoming medical meeting.”


Merck Announces Top-Line Results from Phase 3 Trials Evaluating Gefapixant, an Investigational Treatment for Refractory or Unexplained Chronic Cough [news release]. Merck website. Published March 17, 2020. Accessed March 24, 2020.

© 2024 MJH Life Sciences

All rights reserved.