PDE5A and pulmonary arterial hypertension: Inhibitors of phosphodiesterase 5 (PDE5; e.g., sildenafil or tadalafil), which raise cGMP by blocking its hydrolysis to GMP, are widely used for the treatment of erectile disfunction and pulmonary hypertension (19), and stimulators of soluble guanylyl cyclases (e.g., vericiguat or riociguat), which stimulate cGMP synthesis, are used as treatments for pulmonary hypertension and heart failure (17).