GSK’s $2bn bid on Bellus Health has taken a knock, as the British pharma giant is terminating the late-stage refractory chronic cough (RCC) development programme for the biotech’s lead drug, camlipixant, after it deemed the therapy “unlikely to transform patient care”.
This comes after the P2X3 receptor antagonist posted mixed results across the Phase III CALM-1 and CALM-2 studies (NCT05599191; NCT07650084). During the first study, conducted across 200 global locations, a 50mg twice-daily dose of the drug triggered statistically significant reductions in coughing frequency during a 24-hour period over placebo at week 12 – meeting the trial’s primary endpoint. However, camlipixant failed to demonstrate the same impact in the CALM-2 study conducted in China.
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A lower, 25mg twice-daily dose of camlipixant also offered no significant impact on cough frequency or secondary endpoint measures in either of the CALM studies – leading GSK to deem the drug’s efficacy “limited” in RCC.
While camlipixant was proven safe and tolerable for use and demonstrated moderate efficacy, GSK has opted to stop the drug’s development in RCC. According to Jefferies, this rules out a “potential $1bn opportunity” in RCC for GSK – a move it says is disappointing but manageable as a setback due to the company’s strong focus on deals in recent months that could add revenue potential.
However, all is not lost with camlipixant, as GSK is continuing the Phase IIb BALANCE trial (NCT07519395) on the drug in two forms of irritable bowel syndrome (IBS). The study is slated for completion in March 2027, as per ClinicalTrials.gov.
P2X3 receptor antagonists have a mixed run
With camlipixant no longer in development for RCC, another drug has been added to the list of failed P2X3 receptor antagonists in this indication, as the class is plagued by various efficacy and safety concerns.
Previously, Bayer abandoned its development programme for its P2X3 receptor antagonist, eliapixant, in 2022 due to concerns around the drug’s safety profile. Before this, the German pharma company also dropped development of filapixant, another P2X3 receptor antagonist, due to higher rates of taste issues linked to the drug.
Shionogi also appears to have stopped the development of its offering, sivopixant, which is no longer listed in the Japanese pharma’s pipeline. However, through a partnership with Apnimed, Shionogi is jointly developing SASS-01, a combination of sivopixant and a second undisclosed compound, for the treatment of sleep apnoea.
Currently, there are no US Food and Drug Administration (FDA) approved medications to treat RCC, and patients generally rely on treatment with off-label neuromodulators like gabapentin or tricyclic antidepressants. While MSD’s (Merck & Co) P2X3-targeting therapy, Lyfnua (gefapixant), is approved for use in the UK, EU, Japan and Switzerland, the FDA refused to greenlight the drug due to its perceived lack of efficacy in this patient population.
