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Merck’s gefapixant successful in late-stage chronic cough studies

September 8, 2020

Following up on its initial announcement in March, Merck (NYSE:MRK) announces positive detailed results from two Phase 3 clinical trials, COUGH-1 and COUGH-2, evaluating gafapixant in adult patients with refractory or unexplained chronic cough.

The 45 mg dose (twice daily) met the primary efficacy endpoint in both studies, demonstrating a statistically significant reduction in 24-hour cough frequency at week 12 (COUGH-1) versus placebo (geometric mean coughs/hour = 18.24 at baseline compared to 7.05 at primary endpoint, 32.9% relative reduction; p=0.041) and statistically significant reduction in 24-hour cough frequency at week 24 (COUGH-2) (baseline = 18.55 vs. 6.83 at primary endpoint, 26.1% relative reduction; p=0.031).

The 15 mg dose failed to achieve the primary endpoint in either trial.

No new safety signals were reported. The discontinuation rates for the 45 mg dose in COUGH-1 & 2 were 15% and 20%, respectively, compared to 3% and 8%, respectively, in the 15 mg dose arm and 3% and 5%, respectively, in the control arm. Mild-to-moderate taste-related adverse events were the most common, 58.0%/68.6% for 45 mg, 10.7%/19.5% for 15 mg and 3.3%/8.3% for placebo.

Gefapixant is an orally administered selective P2X3 receptor antagonist. Excessive activation of P2X3 receptors is associated with hyper-sensitization of sensory neurons which, in the airways and lungs, triggered by injury or infection, can cause chronic cough (cough that lasts more t eight weeks).

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