Clinical and hemodynamic improvements after adding ambrisentan to background PDE5i therapy in patients with pulmonary arterial hypertension exhibiting a suboptimal therapeutic response (ATHENA-1).

•This study evaluates the addition of ambrisentan to patients with an unsatisfactory response to PDE5i monotherapy.•The addition of ambrisentan was associated with hemodynamic, functional, and biomarker improvement compared to baseline.•Significant improvements were observed in PVR (−33%), mPAP (−11%), and CI (+24%) following 24 weeks of add-on ambrisentan.•At week 24, 6MWD, NT-proBNP, and WHO functional class showed improvements from baseline.•Adverse events were consistent with known effects of ambrisentan, but 10% of patients discontinued because of them.