Ambrisentan for Early Low-Risk Pulmonary Arterial Hypertension

Prior treatment

• Patients currently receiving PAH specific medications, regardless of whether mPAP is between 20-25 mmHg. PAH specific medications include endothelin receptor antagonists (ERAs; e.g., bosentan, ambrisentan, macitentan), phosphodiesterase type 5 inhibitors (PDE5i; e.g., sildenafil, tadalafil, vardenafil), prostacyclin analogs (e.g., iloprost, epoprostenol, treprostinil, beraprost), soluble guanylate cyclase stimulators (e.g., riociguat). Intermittent use of PDE5 inhibitors for the treatment of male erectile dysfunction is permitted;
• Participation in any clinical drug trial within 4 weeks prior to screening and/or planned participation in another clinical drug trial during this study;

Other illness

• Pulmonary veno-occlusive disease (PVOD);
• Within 6 months after congenital heart disease surgical repair or percutaneous closure procedure;
• Uncontrolled hypertension, defined as blood pressure \> 160/90 mmHg at rest and/or \> 220/120 mmHg under stress conditions;

Lab values

• Clinically significant anemia, defined as hemoglobin concentration below 75% of the lower limit of normal;
• Renal insufficiency, defined as estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m² within 3 months prior to enrollment;
• Elevated Alanine Aminotransferase （ALT） and/or Aspartate Aminotransferase （AST） exceeding 3 times the upper limit of normal (ULN);

Other

• Intolerance to ambrisentan or its excipients;
• Pulmonary capillary hemangiomatosis (PCH);
• Group II-V PH;
• Systolic blood pressure \< 85 mmHg;
• Expected life expectancy of less than 1 year;
• Pregnant or breastfeeding women.

• Age ≥ 18 years;
• mPAP \> 20 mmHg and \< 25 mmHg, pulmonary vascular resistance (PVR) \> 2 WUs and ≤ 3 WUs, and pulmonary arterial wedge pressure (PAWP) ≤ 15 mmHg via right heart catheterization (RHC); RHC measurement will be accepted if it was done within 7 days before enrollment;
• Group I PAH, including idiopathic PAH (IPAH), heritable PAH (HPAH), Drug- and toxin-induced PAH, associated with connective tissue disease (connective tissue disease at good control), associated with portal hypertension, associated with congenital heart disease;
• At low risk based on the 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension three-strata risk-assessment model;
• The subject or a legally authorized representative must understand the study requirements, agree to the treatment procedures, and provide written informed consent before any study-specific procedures are performed;
• The subject must demonstrate a willingness and ability to comply with all protocol requirements.