Disclosed are compositions and pharmaceutical compositions comprising macitentan (depicted) or its salt and a prostacyclin receptor (IP) agonist. The prostacyclin receptor agonists are selected from: prostinil, epoprostenol, iloprost, beraprost, 2-{ 4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy} -N-(methylsulfonyl)acetamide, { 4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy} acetic acid, and pharmaceutically acceptable salts thereof. The compositions are useful for treating a disease wherein endothelin is involved, such as hypertension, pulmonary hypertension (including pulmonary arterial hypertension), diabetic arteriopathy, heart failure, erectile dysfunction, angina pectoris or pulmonary fibrosis.
