Chasing Merck & Co, Bayer builds case for cough drug eliapixant

Bayer says its drug candidate for chronic cough – eliapixant – has hit the mark in a phase 2b trial, putting it in hot pursuit of Merck & Co's gefapixant, which was filed for approval in March.

The orally-active P2X3 receptor antagonist, also known as BAY1817080, hit the main objective of the study, which was to reduce the average hourly cough frequency based on 24-hour sound recordings compared to placebo after 12 weeks of twice-daily treatment.

The actual results will not be available until they are presented at a future medical congress, but they should put Bayer on track to start studies that could be used to support regulatory approvals for chronic cough. However, a spokesperson for the company would not comment on plans for a phase 3 programme.

At the moment there are no approved therapies for suppressing chronic cough – defined as lasting for eight weeks or more – and the P2X3 receptor antagonists are the front runners among drug candidates vying to bring that situation to an end.

It has been estimated that chronic cough affects up to 10% of the US population, with one in five of them getting no benefit from current treatment options such as opioids and corticosteroids.

Merck is well out in front with gefapixant, with a decision from the FDA due in December. The drug reported positive results from two phase 3 trials in 2020 that also showed a significant reduction in 24-hour cough frequency, although the actual reductions (18% and 15%) were less impressive than the 38% reduction that had been seen in a phase 2 study.

Another potential weakness for Merck's drug is that it seems to have an effect on taste sensation at the 45mg dose selected to take forward into regulatory filings, as the lower 15mg tested in trials didn't hit its efficacy target.

The new data keeps Bayer marginally ahead of another player, Bellus Health, whose P2X3 drug BLU-5937 is also in a phase 2b trial in refractory chronic cough with results expected later this year.

P2X3 receptors are found on sensory nerve cells and appear to get more numerous after nerve injury or inflammation, with a number of pathological consequences. They are thought to become over-activated in chronic cough, playing a role in the hyper-sensitisation of neurons in airways that trigger the cough reflex.

Other potential indications include endometriosis, overactive bladder and neuropathic pain, and Bayer is also running phase 2 trials of eliapixant in all these indications.

The P2X3 receptor antagonist was discovered as part of a strategic R&D alliance with Evotec – focused on endometriosis – that began in 2012 and was brought to a close in 2017. The two companies launched a second partnership in 2016 focusing on kidney diseases.

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