Merck Receives FDA Complete Response Letter for Chronic Cough Drug Candidate Gefapixant

The US Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) regarding the New Drug Application for gefapixant, an investigative receptor antagonist therapy from Merck seeking approval for the treatment of refractory or unexplained chronic cough.

The selective P2X3 receptor antagonist was supported by findings from the phase 3 COUGH-1 and COUGH-2 trials, a pair of multinational randomized studies showing 45 mg gefapixant reduced 24-hour cough frequency in patients by 18.45% (95% CI, -32.92 to -0.86; P = .041) and 14.64% (95% CI, -26.07 to -1.43; P = .031), respectively, by 24 weeks versus placebo.

The FDA’s letter to Merck regarding the application included a request for additional information “related to measurement of efficacy,” the company stated in a release.

“The CRL was not related to the safety of gefapixant,” the statement read. “Merck is reviewing the letter and will meet with the agency to discuss next steps.”

Merck leadership expressed their commitment to advancing the regulatory status of gefapixant, which would be the first newly approved drug for chronic cough in 6 decades.

Stuart Green, MD, Vice President of Late Stage Development at Merck, previously told HCPLive the difficulty within the market to identify and progress a new viable drug for chronic cough has been in actually understanding the mediating pathways associated with the condition.

“What we find is that there’s many different pathways, but some of these appear to more important in disease states than others,” he explained. “It’s because of advances in developing not only the understanding of the science, but drugs than can selectively target those pathways, that we’ve now been able to do the kind of studies that allow us to hopefully demonstrate benefit for people with this condition.”