Gefapixant 50 mg twice daily significantly reduced cough frequency in patients with refractory chronic cough and unexplained chronic cough after 12 weeks, according to randomized controlled trial results published in Lancet Respiratory Medicine.

Chronic cough, defined as a cough that lasts longer than 8 weeks, affects 4% to10% of adults worldwide; however, no effective licensed therapies exist. Gefapixant is a P2X3 receptor antagonist that has demonstrated a significant reduction in cough frequency compared with placebo in patients with refractory chronic cough.

Researchers sought to evaluate the effectiveness of 3 doses of gefapixant (7.5 mg, 20 mg, and 50 mg twice daily) compared with placebo in reducing cough frequency during waking hours in 253 patients with refractory chronic cough or unexplained chronic cough after 12 weeks of treatment ( Identifier: NCT02612610).

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The patients’ geometric mean awake cough frequency was 18.2 coughs per hour with placebo, and 14.5 coughs per hour (geometric SD, 3.7) with 7.5 mg, 12.0 coughs per hour (geometric SD, 4.2) with 20 mg, and 11.3 coughs per hour (geometric SD, 2.8) with 50 mg gefapixant. The estimated percentage change relative to placebo was -22.0% (P =.0097) with 7.5 mg, -22.2% (P =.093) with 20 mg, and -37.0% (P =.0027) with 50 mg gefapixant. The most common adverse effect reported was dysgeusia, occurring in 3 patients with placebo, 6 patients with 7.5 mg, 21 patients with 20 mg, and 30 patients with 50 mg gefapixant.  

“Our study shows that gefapixant, a P2X3 receptor antagonist, has antitussive efficacy sustained over a 12-week period,” stated the authors. “Gefapixant therefore shows promise as a novel therapy for chronic cough, and further studies examining longer-term antitussive benefit are warranted.”

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Disclosure: This clinical trial was supported by Afferent Pharmaceuticals (acquired by Merck & Co., Inc., Kenilworth, New Jersey, USA).


Smith JA, Kitt MM, Morice AH, et al; on behalf of the Protocol 012 Investigators. Gefapixant, a P2X3 receptor antagonist, for the treatment of refractory or unexplained chronic cough: a randomised, double-blind, controlled, parallel-group, phase 2b trial [published online February 25, 2020]. Lancet Respir Med. doi:10.1016/ S2213-2600(19)30471-0