Background: Despite advances in the management of pulmonary arterial hypertension (PAH), the mortality rate remains excessive. Long-term efficacy evaluations are needed to guide therapeutic management. The purpose of this study is to present 1-year observational data with two endothelin antagonists, sitaxsentan and bosentan, in a prospective, open-label study.
Methods: The present study was a prospective, international, multicenter, randomized, open-label extension of the Sitaxsentan To Relieve Impaired Exercise-2 trial. All-cause mortality, time to discontinuation (all causes) from monotherapy, time to discontinuation due to adverse events, time to elevations in and time to discontinuation due to elevated hepatic transaminases, and time to first clinical worsening event were evaluated. Patients initially receiving sitaxsentan at 50 mg were excluded from the main analysis. The distributions of time-to-event variables are estimated using Kaplan-Meier methods, and treatment effects are evaluated using the Cox proportional hazards model.
Results: Patients treated with sitaxsentan at 100 mg had 96% overall survival and a 34% risk for a clinical worsening event by 1 year. In addition, there was a 6% risk of elevated aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) levels > 3 x upper limit of normal range (ULN) at 1 year and a 15% risk of discontinuation due to adverse events. Patients treated with bosentan had 88% overall survival and a 40% risk of a clinical worsening event by 1 year. In addition, there was a 14% risk for elevated AST and/or ALT levels > 3 x ULN at 1 year and a 30% risk of discontinuation due to adverse events.
Conclusions: At 1 year, sitaxsentan therapy appears safe and efficacious for patients with PAH; reductions in mortality and the risk for clinical worsening events provide support for durability of efficacy.