Merck announced topline data from 2 ongoing pivotal phase 3 trials (COUGH-1 and COUGH-2) for gefapixant (MK-7264) for the treatment of 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. 

COUGH-1 and COUGH-2 are randomized, double-blind, placebo-controlled studies that enrolled 732 and 1317 adult patients with refractory or unexplained chronic cough for at least 1 year, respectively. Both studies randomized patients to 1 of 3 cohorts: gefapixant 45mg or 15mg twice daily, or placebo. The primary efficacy end points were 24-hour coughs per hour at week 12 (COUGH-1), and 24-hour coughs per hour at week 24 (COUGH-2), measured using an ambulatory audio recording device. 

Findings from both studies demonstrated that gefapixant 45mg met the primary end point achieving a statistically significant decrease in 24-hour coughs per hour at weeks 12 and 24 compared with placebo. Gefapixant 15mg did not meet the primary end point in either study.

With regard to safety, gefapixant was consistent with that observed in previous studies. Full study details will be shared at an upcoming medical meeting. 

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