Complete Response Letter for gefapixant, an investigational, non-narcotic, oral selective P2X3 receptor antagonist, under development for the treatment of refractory chronic cough – Merck

Merck Inc., known as MSD outside of the United States and Canada, announced that the FDA has issued a Complete Response Letter (CRL) regarding Merck’s New Drug Application (NDA) for gefapixant, an investigational, non-narcotic, oral selective P2X3 receptor antagonist, under development for the treatment of refractory chronic cough (RCC) or unexplained chronic cough (UCC) in adults . In the CRL, the FDA concluded that Merck’s application did not meet substantial evidence of effectiveness for treating RCC and UCC. The CRL was not related to the safety of gefapixant. Merck is reviewing the FDA’s feedback to determine next steps.

Chronic cough is defined as a cough lasting longer than 8 weeks. In adults with RCC, the cough persists despite appropriate treatment of underlying conditions such as asthma or gastroesophageal reflux disease, and UCC is a cough where the underlying cause cannot be identified despite a thorough evaluation.