PDE5A and pulmonary arterial hypertension: To address this hypothesis, a Phase III clinical trial was performed with the anti-cancer agent imatinib in patients with PAH and receiving background standard-of-care (SOC) therapy [2]; current SOC for PAH typically involves the use of vasodilators, including endothelin receptor antagonists (ERAs), phosphodiesterase-5 (PDE-5) inhibitors, and prostacyclins [3].