Effects of clazosentan on cerebral vasospasm-related morbidity and all-cause mortality after aneurysmal subarachnoid hemorrhage: two randomized phase 3 trials in Japanese patients

Objective: Clazosentan has been investigated globally for the prevention of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). The authors evaluated its effects on vasospasm-related morbidity and all-cause mortality following aSAH in Japanese patients.

Methods: Two similar double-blind, placebo-controlled phase 3 studies were conducted in 57 Japanese centers in patients with aSAH, after aneurysms were secured by endovascular coiling in one study and surgical clipping in the other. In each study, patients were randomly administered intravenous clazosentan (10 mg/hr) or placebo (1:1) starting within 48 hours of aSAH and for up to 15 days after aSAH. Stratified randomization based on World Federation of Neurosurgical Societies grade was performed using a centralized interactive web response system. Vasospasm-related morbidity and all-cause mortality within 6 weeks post-aSAH, including new cerebral infarcts and delayed ischemic neurological deficits as well as all-cause mortality, were the first primary endpoint in each study. The second primary endpoint was all-cause morbidity (new cerebral infarct or delayed ischemic neurological deficit from any causes) and all-cause mortality (all-cause morbidity/mortality) within 6 weeks post-aSAH. The incidence of individual components of the primary morbidity/mortality endpoints within 6 weeks and patient outcome at 12 weeks post-aSAH (including the modified Rankin Scale scores) were also evaluated. The above analyses were also performed in the population pooled from both studies.

Results: In each study, 221 patients were randomized and 220 were included in the full analysis set of the primary analysis (109 in each clazosentan group, 111 in each placebo group). Clazosentan significantly reduced the incidence of vasospasm-related morbidity and all-cause mortality after aneurysm coiling (from 28.8% to 13.6%; relative risk reduction 53%; 95% CI 17%-73%) and after clipping (from 39.6% to 16.2%; relative risk reduction 59%; 95% CI 33%-75%). All-cause morbidity/mortality and poor outcome (dichotomized modified Rankin Scale scores) were significantly reduced by clazosentan after preplanned study pooling. Treatment-emergent adverse events were similar to those reported previously.

Conclusions: Clazosentan significantly reduced the combined incidence of vasospasm-related morbidity and all-cause mortality post-aSAH with no unexpected safety findings. Clinical trial registration nos.: JapicCTI-163368 and JapicCTI-163369 (https://www.clinicaltrials.jp).