GSK has ended development of camlipixant in chronic cough after delivering mixed phase 3 data, dealing a major blow to a potential blockbuster that analysts saw as the key 2026 catalyst for the drugmaker.
Britain’s GSK acquired the P2X3 receptor antagonist when it bought Bellus Health for $2 billion in 2023. By then, Bellus had started a pair of phase 3 trials of camlipixant in refractory chronic cough (RCC). Data were originally due in 2024 and 2025. Yet, as Merck & Co. grappled with two FDA rejections for its rival RCC candidate, the camlipixant readouts slipped to 2026.
The belated data disappointed GSK. In the Calm-1 trial, the high dose of camlipixant drove statistically significant reductions in 24-hour cough frequency versus placebo at Week 12. But camlipixant fell short on other endpoints across Calm-1 and Calm-2.
High-dose camlipixant was statistically no better than placebo at reducing 24-hour cough frequency at Week 24 of the Calm-2 trial, causing that study to miss its primary endpoint. The low dose failed to meet the bar for statistical significance in either trial. With both trials missing key secondary endpoints, GSK characterized the efficacy as “limited” and “unlikely to transform patient care.”
That conclusion prompted GSK to end development of camlipixant in RCC. A phase 2b study of the candidate in adults with irritable bowel syndrome (IBS) is continuing. GSK started the IBS trial in April, listing March 2027 as the primary completion date on the federal trials database.
The placebo-like incidence and severity of treatment-related adverse events linked to camlipixant were one positive from the RCC trials. Merck’s rival P2X3 receptor antagonist, gefapixant, was undone in part by taste disturbances that risked unblinding the study. GSK predicted that camlipixant could avoid those problems through increased selectivity for P2X3 over P2X2, which is present in the taste buds.
Betting it could avoid the pitfalls that scuttled gefapixant in the U.S., GSK forecast camlipixant peak sales could rise above 2.5 billion pounds ($3.4 billion). In May, Guggenheim Securities analysts said in a note to investors that the camlipixant data “may be the key potential catalyst to drive mid- to long-term revenue upgrades this year.”
Stripped of the catalyst, GSK has lost a sales driver that could have helped push revenue up toward its 2031 target of 40 billion pounds ($53.7 billion). Analysts were skeptical of GSK’s ability to hit the target even before the camlipixant flop, with Guggenheim team forecasting 2031 sales of 35.9 billion pounds ($48.2 billion) in May.