The current approved drugs targeting these three pathways, including prostacyclin (PGI2), phosphodiesterase type-5 (PDE5) inhibitors, and endothelin receptor antagonists (ERAs), have been shown to be effective, however, PAH remains a severe clinical condition and the long-term survival of patients with PAH is still suboptimal. The gene discussed is PDE5A; the disease is pulmonary arterial hypertension.