USFDA declines to approve Merck chronic cough drug Gefapixant

The FDA's decision was not related to the drug's safety, Merck said, adding that it is reviewing the agency's feedback to determine next steps.

Failing to secure marketing approval the first time, Merck carried out additional efficacy analyses of the drug to address questions raised by the health regulator. The results from the additional analyses were generally consistent with those from the late-stage trial, Merck said.

The FDA's decision gives some breathing room to rival GSK's chronic cough treatment camlipixant, which is in late-stage development with anticipated regulatory approval and launch in 2026.

Merck's gefapixant works by blocking receptors that stimulate the nerves and trigger the urge to cough.

The drug, which was given twice a day, was evaluated across two late-stage trials where a higher dose showed statistically significant reduction in the average number of coughs per hour over a 24-hour period compared to a placebo, according to Merck.

The European Union and Japan have approved Merck's drug for the condition and it is sold under the brand name Lyfnua.