The aim of this study is to demonstrate that clazosentan, administered as a continuous intravenous infusion at 5 mg/h until Day 14 post aneurysmal subarachnoid hemorrhage (aSAH), reduces the incidence of cerebral vasospasm -related morbidity and all-cause mortality within 6 weeks post-aSAH treated by surgical clipping. The primary endpoint of the study is the occurrence of cerebral vasospasm-related morbidity, and mortality of all-causes within 6 weeks post-aSAH, defined by at least one of the following: Death (all causes). New cerebral infarct(s) due to cerebral vasospasm as either the primary or relevant contributing cause, or not adjudicated to be entirely due to causes other than vasospasm. Delayed ischemic neurological deficit (DIND) due to cerebral vasospasm as either the primary or relevant contributing cause, or not adjudicated to be entirely due to causes other than vasospasm. Neurological signs or symptoms (depending on state of consciousness), in the presence of confirmed cerebral vasospasm on angiography (DSA or CTA), leading to the administration of a valid rescue therapy. An independent Critical Events Committee (CEC) will adjudicate whether or not patients meet the primary endpoint and its individual morbidity components.