United Therapeutics specializes in drug development for pulmonary arterial hypertension, a rare and progressive disease marked by abnormally high blood pressure in the arteries of the lungs. The company's therapies for PAH largely focus onthe prostacyclin pathway, and many of its treatments are based on the same molecule, treprostinil. Most of the company's sales are generated within the United States. United Therapeutics also markets a pediatric oncology drug, but its focus largely remains in pulmonary arterial hypertension.