Over the past 20 years, great progress has been made in the treatment of 
pulmonary arterial hypertension (PAH). Available therapies target one of three 
principal pathways: the endothelin (ET), nitric oxide (NO) or the prostacyclin 
(PGI2) pathway. Evidence shows that current drugs, used either as monotherapy or 
in different combinations, can improve exercise capacity, clinical symptoms, 
hemodynamics and even survival in PAH. Unfortunately, the disease remains 
incurable and the prognosis of the disease is still poor. However, existing and 
novel potent antiproliferative therapies are being explored, and new agents 
targeting different and/or additional pathways are likely to become available to 
clinicians in the near future. Promising candidates include tyrosine kinase 
antagonists (e.g. imatinib); soluble guanylate cyclase stimulators (riociguat); 
an oral analog of prostacyclin (selexipag); and a tissue targeting endothelin 
receptor antagonist (macitentan). Phase II or III trials have either been 
completed or are underway to evaluate the safety and efficacy of these various 
therapies.