PDE5A and congenital heart disease: Adults (≥18 years) with symptomatic PAH (idiopathic, heritable, connective tissue disease-associated, anorexigen-induced, or congenital heart disease-associated), Stable background therapy with ERAs and/or PDE5-Is for >12 weeks before screening, Baseline PVR > 400 dyn·s·cm−5, Two 6MWD tests of 150–500 m (within ±15% of each other).