Clinical Research Study With Clazosentan to Evaluate Its Effects on Preventing Complications Due to the Narrowing of the Blood Vessels (Vasospasm) in the Brain, Caused by Bleeding Onto the Surface of the Brain

Inclusion Criteria: * Written informed consent to participate in the study must be obtained from the subject or proxy/legal representative at any time from hospital admission to prior to initiation of any study-mandated procedure, * Males and females aged 18 to 70 years (inclusive, at hospital admission), * Participants with a ruptured saccular aneurysm, angiographically confirmed by DSA or CTA, which has been successfully secured within 72 hours of rupture, by surgical clipping or endovascular coiling, * WFNS (World Federation of Neurosurgical Societies) grades 1-4 (based on Glasgow Coma Scale \[GCS\]) assessed after recovery from the aneurysm-securing procedure and after external ventricular drainage for hydrocephalus, if required. * Participants must meet the criteria for the high-risk prevention group: Subjects with a "thick and diffuse clot" (thick and diffuse is defined as a thick confluent clot, more than 4 mm in thickness, involving 3 or more basal cisterns) on the hospital admission CT scan, absence of cerebral vasospasm at the time of randomization, and possibility to start study drug in the ICU (or equivalent environment where all protocol assessments can be performed and the Patient Management Guidelines followed), within 96 hours after the time of the aneurysm rupture. * The recruitment into the early treatment group, i.e. participants without a thick and diffuse clot on the hospital admission CT scan who develop asymptomatic or minimally symptomatic moderate to…