The U.S. FDA has issued a second complete response letter for Merck’s chronic cough treatment, again citing effectiveness as the main concern.
Gefapixant is non-narcotic, oral selective P2X3 receptor antagonist, under development for the treatment of refractory chronic cough (RCC) or unexplained chronic cough (UCC) in adults.
After Merck received its first CRL for gefapixant in January 2022, hopes of approval were dampened this November when the FDA’s Pulmonary-Allergy Drugs Advisory Committee voted 12 to 1 that the evidence does not demonstrate that gefapixant provides a clinically meaningful benefit to adults with refractory or unexplained chronic cough.
In Merck's two studies, a 45 mg dose of gefapixant twice daily reduced cough frequency by 18.45% relative to placebo at 12 weeks (COUGH-1 study) and 14.64% relative to placebo at 24 weeks (COUGH-2 study).
Gefapixant is already approved under the brand name Lyfnua in Japan, Switzerland and the EU for treatment of adults with refractory or unexplained chronic cough. In light of the CRL, Merck says it is reviewing the FDA’s feedback to determine next steps.