placebo + macitentan

This is a combination of a placebo and macitentan. Macitentan is an orally administered small molecule drug classified as an endothelin receptor antagonist, primarily used to treat pulmonary arterial hypertension (PAH). It works by blocking the action of endothelin-1 at both the endothelin A (ETA) and B (ETB) receptors, leading to vasodilation and reduced cell proliferation in the pulmonary arteries. The addition of "placebo" indicates this combination is typically used in clinical trial settings as a control or comparator arm, where one group receives only macitentan while another receives a placebo plus macitentan for blinding or study design purposes[1][2][6].