FDA Raises Efficacy Concerns About Merck’s Chronic Cough Drug Ahead of Adcomm Meeting
17 Nov 2023
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Pictured: Exterior of an FDA building/iStock, Grandbrothers
Merck’s drug to treat chronic cough, the P2X3 receptor antagonist gefapixant, is facing some concerns about its effectiveness from the FDA ahead of Friday’s advisory committee meeting.
According to the FDA’s briefing document, the agency’s assessment of the data that has been submitted by Merck is that gefapixant “showed a small reduction in cough frequency” while uncertainty remains as to “whether the effect is clinically meaningful.”
Merck’s briefing document makes the case for a clinically meaningful reduction in cough frequency in patients, emphasizing that the drug’s efficacy claim is based on two Phase III trials that looked at gefapixant in adults.
The primary endpoint was the reduction of 24-hour cough frequency, as measured by the VitaloJAK cough counting system. Merck maintains that both studies met the primary endpoint criteria. Those with a 45-mg dose had a reduction of 18.45%, a p-value of p=0.041% at week 12, and a 14.64% reduction at week 24, earning a p-value of p=0.031. The 15-mg section did not “differentiate” from the placebo, according to the company.
“Based on this result, the proposed dosing regimen is gefapixant 45 mg [twice daily] (and the results presented in this document largely focus on this regimen),” according to Merck.
However, the FDA document notes that disturbance or loss of taste occurred in up to 65% of participants taking the drug, while around 14% of patients had discontinued the trial.
“With a large placebo response and wide range of cough frequencies at baseline, we question if the small treatment difference in cough frequency is noticeable to patients. What constitutes a meaningful reduction in cough frequency is not established; therefore, we ask the Committee to consider whether the change in cough frequency with gefapixant will be perceptible and meaningful to patients,” the FDA said in its briefing document.
Gefapixant has had a rough path in the regulatory approval process. After the drug’s NDA was accepted to be reviewed by the FDA in 2021, it encountered a speed bump a year later. In January 2022, the regulator issued a Complete Response Letter to Merck. While the company did not explain why the CRL was handed down, safety issues were not the cause and Merck said it remained “committed” to advancing the drug.
Friday’s adcomm meeting for gefapixant comes as competition is bearing down on Merck in the chronic cough treatment arena. In April 2023, GSK inked a $2 billion deal to acquire Canadian biotech Bellus Health, gaining access to its chronic cough candidate camlipixant. That drug is also an antagonist of the P2X3 receptor and had met its primary endpoint in a 2021 clinical trial.
Meanwhile, Bayer jumped out of the chronic cough space last year, abandoning Phase II development of eliapixant, which was being developed for chronic cough and endometriosis, diabetic neuropathic pain and overactive bladder.
Tyler Patchen is a staff writer at BioSpace. You can reach him at tyler.patchen@biospace.com. Follow him on LinkedIn.
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