Objective: To investigate the safety and efficacy of long-term administration of ambrisentan in Japanese adults with pulmonary arterial hypertension (PAH).
Research design and methods: In this open-label extension of a preceding multicenter dose-escalation study, 21 Japanese patients with PAH received treatment with 5 or 10 mg of ambrisentan once daily and were comprehensively evaluated every 12 weeks. The primary endpoint was the safety of long-term ambrisentan administration, as defined by the incidence and severity of adverse events. The secondary (efficacy) endpoints were change in exercise capacity (as indicated by 6-minute walk distance), World Health Organization functional class, Borg dyspnea index, plasma brain natriuretic peptide level, cardiopulmonary hemodynamics, and time to clinical worsening of PAH.
Clinical trial registration: NCT00554619.
Results: The mean total duration of treatment (i.e., including the preceding dose-escalation study) was approximately 139 weeks. There were fewer adverse events related to ambrisentan in this study than in the preceding study, and we identified no new safety signals that might preclude the long-term use of ambrisentan among Japanese adults with PAH. Improvements observed in efficacy endpoints in the preceding study were maintained in the present study.
Limitations: This study did not include a control group and lacked the statistical power to reach definite conclusions regarding the efficacy of ambrisentan.
Conclusion: Our results suggest that long-term administration of ambrisentan is well tolerated and efficacious for Japanese adults with PAH.