Background: Clazosentan has been explored worldwide for the prophylaxis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). In a dose-finding trial (CONSCIOUS-1) conducted in Israel, Europe, and North America, clazosentan (1, 5, and 15 mg/h) significantly reduced the incidence of cerebral vasospasm, but its efficacy in Japanese and Korean patients was unknown. We conducted a double-blind comparative study to evaluate the occurrence of cerebral vasospasm in Japanese and Korean patients with aSAH. Methods: The aim of this multicenter, double-blind, randomized, placebo-controlled, dose-finding phase 2 clinical trial, was to evaluate the efficacy, pharmacokinetics, and safety of clazosentan (5 and 10 mg/h) against cerebral vasospasm after clipping surgery in Japanese and Korean patients with aSAH. Patients aged between 20 and 75 years were administered the study drug within 56 h after the aneurysm rupture and up to day 14 post-aSAH. The incidence of vasospasm, defined as an inner artery diameter reduction of major intracranial arteries ≥34% based on catheter angiography, was compared between each treatment group. Cerebral infarction due to vasospasm at 6 weeks and patients' outcome at 3 months was also compared. Results: Among 181 enrolled patients, 158 completed the study and were analyzed. The incidence of vasospasm up to day 14 after aSAH onset was 80.0% in the placebo group (95% CI 67.0-89.6), 38.5% in the 5 mg/h clazosentan group (95% CI 25.3-53.0), and 35.3% in the 10 mg/h clazosentan group (95% CI 22.4-49.9), indicating that the incidence of vasospasm was significantly reduced by clazosentan treatment (placebo vs. 5 mg/h clazosentan, p < 0.0001; placebo vs. 10 mg/h clazosentan, p < 0.0001). The occurrence of cerebral infarction due to vasospasm was 20.8% in the placebo group (95% CI 10.8-34.1), 3.8% in the 5 mg/h clazosentan group (95% CI 0.5-13.2), and 4.2% in the 10 mg/h clazosentan group (95% CI 0.5-14.3), indicating that clazosentan significantly reduced the occurrence of cerebral infarctions caused by vasospasm (placebo vs. 5 mg/h clazosentan, p = 0.0151; placebo vs. 10 mg/h clazosentan, p = 0.0165). The overall incidence of all-cause death and/or vasospasm-related morbidity/mortality was significantly reduced in the 10 mg/h clazosentan group compared with the placebo group (p = 0.0003). Conclusion: These results suggest that clazosentan prevents cerebral vasospasm and subsequent cerebral infarction, and could thereby improve outcomes after performing a clipping surgery for aSAH in Japanese and Korean patients.

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Tolerability, safety, pharmacokinetics, and pharmacodynamics of orally administered macitentan at 3 and 10 mg once daily for 10 days were investigated in 16 healthy Japanese male subjects in a randomized, placebo-controlled, double-blind, single-center study. Plasma concentrations of macitentan were found to peak at 5 hr, with a mean terminal elimination half-life of approximately 11 hr, for both doses of macitentan. Furthermore, the active metabolite of macitentan, ACT-132577, demonstrated a longer elimination half-life(approximately 48 hr). Area under the plasma concentration-time curve(AUC)of endothelin-1 was significantly higher in the macitentan 10-mg group compared with the placebo group (exploratory p value, 0.0154). No critical issues regarding the safety and tolerability of macitentan were observed, including time-matched electrocardiographic (ECG)evaluations. The results of this study in healthy Japanese male subjects corroborate with previous studies in Caucasian and Korean subjects. In conclusion, the macitentan dose range from 3 to 10 mg had a good safety and tolerability profile in healthy Japanese male subjects, and its pharmacokinetics and pharmacodynamics were dose-dependent without ethnic differences.