AstraZeneca’s clinical trial programme for zibotentan has suffered a major setback after the drug failed to achieve its primary goal in a late-stage study with prostate cancer patients.

The Anglo-Swedish drumgaker said yesterday that a Phase III study assessing the drug for the treatment of men with metastatic castration resistant prostate cancer (CRPC) did not show a significant improvement in overall survival.

Zibotentan is a novel once daily pill designed to block the endothelin pathway, which becomes uncontrolled as prostate cancer advances and so encourages the spread of the disease.

Following its failure to hit the trial’s key target, AZ said it is not planning any regulatory filings for zibotentan at this time, but stressed that the programme is not dead in the water as two other clinical trials in prostate cancer are still ongoing, the results of which are expected next year.

Meanwhile, Actelion also suffered a blow after its experimental drug clazosentan failed to impress in a study of patients with brain haemorrhage.

The Swiss drugmaker’s shares fell nearly 10% after it reported that clazosentan missed the primary endpoint of the study – a significant reduction in vasospasm-related morbidity and all-cause mortality in clipped patients following aneurysmal subarachnoid haemorrhage.

Initial results from the CONSCIOUS-2 (Clazosentan to Overcome Neurological iSChaemia and Infarct OccUrring after Subarachnoid haemorrhage) study showed that, while the drug was associated with a relative risk reduction of 17% versus placebo, the difference was not significant.

Sarasin analyst David Kaegi told Reuters that CONSCIOUS-2 was “potentially the most important catalyst for Actelion shares this year”, and that the drug had been expected to pull in annual sales of around SwFr 500 million to SwFr 1 billion.

But the results have thrown the future of clazosentan into doubt, with Actelion only saying at this point that it will continue to focus on its growing its existing business. However, an update on the development programme is expected with the group’s third-quarter results later this year.