Pulmonary arterial hypertension (PAH) is a highly debilitating disease characterized by severe constriction of the blood vessels in the lungs, leading to high pulmonary arterial pressures, extreme shortness of breath and frequently heart failure.

As a result of our acquisition of Myogen, Inc. in 2006, we obtained rights to two endothelin receptor antagonists - Letairis® for the treatment of PAH and darusentan for resistant hypertension. Endothelin receptor antagonists are a new class of drug used to treat a variety of diseases including PAH.

Darusentan, being developed as a new treatment for resistant hypertension, is currently in Phase III clinical trials. We also have an active research effort on the identification of endothelin receptor antagonists for the treatment of chronic heart failure and related cardiovascular disorders.