Analysis of the phase 3 results on camlipixant, which was a major potential blockbuster expected to be the standout catalyst for the drugmaker in 2026, has caused a major setback for the company.
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). Originally, data were to be submitted for 2024 and 2025. However, Merck & Co. had two FDA rejections for its competitor RCC candidate, which caused the camlipixant readouts to be pushed back to 2026.
The late data fell short of GSK’s expectations. At Week 12, the high dose of camlipixant was the only dose that resulted in a statistically significant reduction in 24-hour cough frequency compared to placebo in the Calm-1 trial. However, camlipixant was not as effective on other endpoints in 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. In both trials, the low dose was not statistically significant. Both trials failed to meet important secondary endpoints, according to GSK, and the results suggest efficacy was “limited” and “unlikely” to change patient care.
That led to GSK terminating its RCC development program for camlipixant. A phase 2b study of the candidate in adults with irritable bowel syndrome (IBS) is continuing. GSK began the IBS trial in April, and listed March 2027 as the trial’s primary completion date on the federal trials database.
One upside from the RCC trials was the incidence and severity of the adverse events associated with camlipixant that were similar to the placebo. Taste disturbances were a partial setback for Merck’s competitor P2X3 receptor antagonist, gefapixant, which could have led to unblinding the trial. GSK said it believed camlipixant would not suffer from those issues because it is more selective toward the P2X3 receptor than the P2X2 receptor (which is found in the taste buds).
GSK estimated that it could sell more than 2.5 billion pounds ($3.4 billion) of camlipixant, which could help it avoid facing the pitfalls that brought gefapixant to a halt in the U.S. Guggenheim Securities analysts noted in a note to investors in May that the camlipixant data could be a “key potential catalyst to support mid to long-term revenue upgrades this year.”
Without the catalyst, GSK is losing a sales boost which could have helped take revenue closer to the 2031 target of 40 billion pounds ($53.7 billion). Even before the camlipixant debacle, analysts doubted whether GSK could reach the target, and the Guggenheim team estimates that its sales in 2031 will be 35.9 billion pounds ($48.2 billion).
GSK has discontinued development of a major investigational cough medicine after disappointing Phase 3 results reduced expectations for the treatment. The decision represents a setback for GSK’s respiratory medicine pipeline and highlights the challenges pharmaceutical companies face when advancing promising therapies into late-stage clinical development.
Why the GSK Decision Matters
The discontinuation is significant for GSK because the candidate had been viewed as a potentially important addition to its respiratory portfolio. However, Phase 3 studies are designed to provide definitive evidence of a medicine’s clinical benefit, and the latest results did not provide sufficient support for continued development.
Following the setback, GSK is expected to concentrate on other innovative medicines and development programs across respiratory disease, immunology, infectious diseases, and oncology. The company’s broader pipeline provides opportunities to offset individual clinical failures and maintain long-term growth.
The termination could influence expectations surrounding GSK’s future respiratory portfolio and pipeline growth. It also illustrates why investors and industry observers closely monitor Phase 3 data, as late-stage outcomes can significantly affect the future value of drug candidates.
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