An orally available dual endothelin receptor (ETR) antagonist with potential antihypertensive and antineoplastic activity. Upon administration, macitentan and its metabolites block the binding of endothelin isoform 1 (ET-1) to type-A and type-B ETR on both the tumor cells and the endothelial cells in the tumor vasculature. This prevents ET-1 mediated signaling transduction which may decrease tumor cell proliferation, progression, and angiogenesis in tumor tissue. ET-1, a potent vasoconstrictor that plays an important role in inflammation and tissue repair, is, together with its receptors, overexpressed varyingly in many tumor cell types.