The Food and Drug Administration (FDA) has accepted for review the New Drug Application (NDA) for gefapixant for the treatment of adults with refractory or unexplained chronic cough.

Gefapixant is an orally administered, selective P2X3 receptor antagonist. It is believed that excessive activation of P2X3 receptors is associated with neuronal hypersensitization in the airways and lungs leading to chronic cough. 

The NDA submission is based on data from the double-blind, placebo-controlled phase 3 studies, COUGH-1 ( NCT03449134) and COUGH-2 ( NCT03449147), which included 730 and 1314 adult patients with refractory or unexplained chronic cough for at least 1 year, respectively. Both studies randomly assigned patients to 1 of 3 cohorts: gefapixant 45mg or 15mg twice daily, or placebo. 

Results from both studies showed that gefapixant 45mg twice daily met the primary end point achieving a statistically significant reduction in 24-hour cough frequency compared with placebo. Additionally, gefapixant 45mg twice daily was associated with a significant reduction in awake coughs per hour (secondary end point), along with a clinically important improvement in cough-related quality of life.

“If approved by the FDA, gefapixant would be the first medicine approved specifically to help these patients, and we look forward to participating in the advisory committee meeting and working with the FDA as they review our application,” said Dr Roy Baynes, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories.

A Prescription Drug User Fee Act (PDUFA) target date of December 21, 2021 has been set for this application.


U.S. FDA accepts Merck’s gefapixant New Drug Application for review. [press release]. Kenilworth, NJ: Merck; March 1, 2021.