Update on the clinical development of gefapixant, a P2X3 receptor antagonist for the treatment of refractory chronic cough.

Chronic cough, or cough lasting >8 weeks, is often associated with underlying medical conditions (ie, asthma, gastroesophageal reflux disease, nonasthmatic eosinophilic bronchitis, and upper-airway cough syndrome). In some patients with chronic cough, treatment of these underlying conditions does not resolve the cough (refractory chronic cough [RCC]), or none of these conditions are present (unexplained chronic cough [UCC]). Despite appropriate medical evaluation, patients with RCC or UCC frequently experience cough persisting for many years, as there are currently no targeted pharmacological approaches approved for the treatment of these conditions. However, the adenosine triphosphate (ATP)-gated P2X3 receptor, a key modulator of the activation of sensory neurons central to the cough reflex, has recently garnered attention as a potential therapeutic target for the treatment of chronic cough. Gefapixant, a first-in-class, non-narcotic, selective antagonist of the P2X3 receptor, recently demonstrated efficacy and was generally well tolerated in phase 2 clinical trials in patients with RCC, validating the utility of targeting this receptor in patients with chronic cough. On the basis of these data, 2 global phase 3 trials, with combined anticipated enrolment exceeding 2000 patients and with treatment durations of up to 1 year, have been initiated. Together, these trials will further evaluate efficacy and safety of gefapixant in the control of cough in patients with RCC or UCC.