Possible future treatment for chronic, unexplained cough
An industry-funded (Afferent Pharmaceuticals/Merck) phase 2(b) study was recently published online in The Lancet Respiratory Medicine. The study investigated gefapixant which is a P2X3 agonist known from previous studies to block a receptor which forms part of the coughing reflex.
This was a randomised controlled trial versus placebo, multi-centred and double-blinded, using much lower doses than in prior studies (previously 600 mg was used). Patients (n=253) with idiopathic cough of 14.5 years duration on average, were randomised to varying doses of gefapixant or placebo. The frequency of coughing was recorded in diaries and by a recording device.
After 12 weeks, there was a statistically significant 37% reduction in coughs per hour in the 50 mg dose group versus placebo. The lower dosing groups did not produce a statistically significant reduction in cough. The most common adverse effect was alteration in sense of taste. Phase 3 trials with more participants and a longer timeframe are underway.