Ethamoxytriphetol (MER-25) is a non-steroidal antiestrogen that acts as a pure antagonist of estrogen receptor signaling. In primate pregnancy models, oral administration of MER-25 at 25 mg/kg BW reduced placental progesterone production by 40–51%, placental mitochondrial P-450scc activity by 37%, and low-density lipoprotein (LDL) uptake by 55–56% compared to untreated controls. This compound is widely used in endocrine research to investigate estrogen-dependent mechanisms in reproduction, placental steroidogenesis, and lipid metabolism.