Among the 5 participants (13%) whose single NT-proBNP level > 1200 ng/L was recorded at the randomized study baseline prior to ambrisentan initiation, 1 had an event of PAH worsening during the extension study, whereas 5/6 participants (83%) who had ≥ 1 recorded NT-proBNP level > 1200 ng/L subsequent to that baseline had an event of PAH worsening or death. This evidence concerns the gene NPPB and pulmonary arterial hypertension.