What is "macitentan"

Macitentan (trade name Opsumit) is an endothelin receptor antagonist (ERA) approved for the treatment of pulmonary arterial hypertension (PAH). The other two ERAs marketed as of 2014 are bosentan and ambrisentan. Macitentan is a dual ERA, meaning that it acts as an antagonist of two endothelin (ET) receptor subtypes, ET and ET. However, macitentan has a 50-fold increased selectivity for the ETA subtype compared to the ETB subtype. The drug received approval from the U.S. Food and Drug Administration (FDA) on October 13, 2013.