GSK Halts Camlipixant Development for Refractory Chronic Cough After Mixed Phase III Results
Key Insights
CALM-1 met its primary endpoint with camlipixant 50mg BID showing statistically significant reductions in 24-hour cough frequency versus placebo at week 12.
CALM-2 failed to reach statistical significance on the same primary endpoint, and the 25mg BID dose missed significance in both trials.
Key secondary endpoints, including the Chronic Cough Diary measure, did not meet target thresholds in either study.
GSK plc announced on 17 July 2026 that it will discontinue development of camlipixant for refractory chronic cough (search) (RCC) following mixed results from the CALM-1 and CALM-2 phase III clinical trials. The two pivotal studies assessed the efficacy and safety of the P2X3 receptor (search) antagonist in adults with RCC, a complex and under-recognised disease with limited treatment options.
The CALM-1 trial met its primary endpoint, with camlipixant 50mg twice daily demonstrating statistically significant reductions in 24-hour cough frequency versus placebo at week 12. However, the sister trial CALM-2 did not reach statistical significance on the same primary endpoint with the 50mg twice-daily dose at week 24. The lower 25mg twice-daily dose failed to achieve statistical significance in either study.
Key secondary endpoints, including a Chronic Cough Diary (CCD) measure, did not meet target thresholds in either trial, further weakening the overall efficacy picture. Across both studies, the overall incidence and severity of treatment-related adverse events were similar between patients receiving camlipixant and those receiving placebo, indicating a tolerable safety profile but insufficient differentiation on efficacy.
"Based on the aggregate data, the limited efficacy demonstrated is unlikely to transform patient care," GSK stated in its announcement. The company has therefore decided not to progress further development of camlipixant in RCC.
Scientific Contribution and Ongoing Development
Despite the disappointing outcome, GSK committed to submitting results from the CALM phase III programme for future presentation and publication, aiming to contribute to the broader scientific understanding of refractory chronic cough (search).
Camlipixant's development story is not entirely over. The phase IIb BALANCE trial (NCT07519395) will continue to evaluate the efficacy and safety of camlipixant in adults with irritable bowel syndrome – diarrhoea (IBS-D) and irritable bowel syndrome – mixed (IBS-M), exploring the molecule's potential in a distinct therapeutic indication.
Background on Camlipixant
Camlipixant (formerly BLU-5937) is a selective P2X3 receptor (search) antagonist designed to offer antitussive effects while minimising taste disturbance, a known class-related side effect of P2X3 inhibition. Preclinical and early clinical work, including a model-based dose-response meta-analysis presented at the American Thoracic Society conference in 2025, had explored the relationship between camlipixant's P2X3 selectivity and taste-related adverse events.
The CALM programme's outcome represents a setback for the RCC field, where patients continue to face a paucity of approved therapeutic options. GSK's decision underscores the challenges of translating early-phase promise into consistent, clinically meaningful phase III results in this heterogeneous patient population.