According to a report by PharmaTimes, clazosentan has failed to meet its primary endpoint in the Phase III CONSCIOUS-2 trial, of superiority over placebo in the prevention of cerebral vasospasm following aneurysmal subarachnoid haemorrhage (aSAH).  

The multicentre CONSCIOUS-2 study enrolled over 1,150 patients with aSAH who had undergone either aneurysmal surgical clipping or coiling to stop the initial bleeding.  Participants were randomised to receive the endothelin receptor antagonist clazosentan (15mg/hour, 5mg/hour and 1mg/hour) or placebo to prevent cerebral vasospasm.  Initial results from the study show that clazosentan was associated with a non-significant relative risk reduction of 17% versus placebo for the primary endpoint of vasospasm-related morbidity and all-cause mortality.  The safety profile was comparable to that seen in previous studies.

The company must now decide whether to carry on with the CONSCIOUS-3 trial, which has an identical primary endpoint to CONSCIOUS-2. This Phase III study is evaluating the efficacy and safety of two doses of clazosentan (5mg/hour or 15mg/hour) against placebo in post-aSAH patients who have been treated with endovascular coiling. As of the end of September 2010, CONSCIOUS-3 had enrolled close to 600 patients out of a target of 1,500.