RAHWAY, NJ, USA I December 20, 2023 I Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced that the U.S. Food and Drug Administration (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.

“We thank our clinical trial participants and investigators for their important contributions that add to the body of knowledge related to chronic cough and help to raise awareness about the significant unmet medical need and the impact of RCC and UCC on patients,” said Dr. Joerg Koglin, senior vice president, global clinical development, Merck Research Laboratories. “Acknowledging the absence of any approved treatments for refractory or unexplained chronic cough, we are disappointed in the FDA’s response to our application for gefapixant.”

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