What this Trial Is About

Pulmonary arterial hypertension (PAH) is a rare, progressive, and potentially fatal disease characterized by increased pulmonary vascular resistance and right ventricular dysfunction. Among the four major molecular pathways involved in PAH pathophysiology-nitric oxide, prostacyclin, activin, and endothelin-1 (ET-1)-the endothelin pathway plays a central role. Endothelin-1 acts on ETA and ETB receptors, inducing vasoconstriction and vascular remodeling. Endothelin receptor antagonists (ERAs) are cornerstone therapies in PAH. Ambrisentan is selective for ETA and associated with a lower risk of hepatotoxicity. Bosentan, a dual ERA (ETA/ETB), has well-established efficacy but a higher incidence of liver enzyme elevation, with approximately 9% of patients experiencing hepatic side effects and about 2% discontinuing therapy due to hepatotoxicity. While transitions between ERAs occur in routine clinical practice, data on their clinical impact are scarce. This prospective, observational, single-center cohort study aims to evaluate the effect of switching from ambrisentan to bosentan on risk stratification using the COMPERA 2.0 and REVEAL Lite 2.0 scores at 3-6 months post-switch. Secondary outcomes include variations in functional class (WHO/NYHA), 6-minute walk distance (6MWD), NT-proBNP levels, incidence of adverse events (with a focus on hepatotoxicity), and hematologic parameters such as anemia. The study will enroll adult patients (≥18 years) with confirmed PAH by right heart catheterization who have undergone a documented switch from ambrisentan 10 mg to bosentan 125 mg within the last 6 months. The primary endpoint is the proportion of patients whose risk category changes post-transition according to COMPERA 2.0 and REVEAL Lite 2.0. The results are expected to provide clinically relevant insights into therapeutic decisions involving ERA transitions in PAH management.

The Impact of ERA Switching on Risk Stratification in Pulmonary Arterial Hypertension