USFDA staff flags concerns about Merck chronic cough drug

The drugmaker's shares were marginally down in afternoon trade.

The concerns were raised after the company had submitted additional efficacy data to the U.S. Food and Drug Administration (FDA), which declined to approve the drug in January last year.

A panel of expert advisers to the FDA is set to meet on Friday to discuss the efficacy of Merck's drug gefapixant.

Staff assessment of the data submitted by Merck showed a small reduction in cough frequency and side effects such as loss of taste in patients who were administered the drug.

There are low expectations for the drug candidate based on efficacy and side effects, Mizuho analyst Mara Goldstein said, adding that it would not be surprising if the drug did not have a positive outcome.

Currently, there are no approved therapies for chronic cough in the United States. The condition is estimated to affect about 10% of the adult population globally and roughly half of those patients do not have an identifiable cause for their cough despite diagnostic tests.

Gefapixant works by blocking receptors that stimulate the nerves and trigger the urge to cough.

The drug 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.

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