Raloxifene hydrochloride (LY156758 hydrochloride) is a second generation selective estrogen receptor modulator (SERM) used to prevent osteoporosis in postmenopausal women. It has estrogen agonist effects on bone and cholesterol metabolism but behaves as a complete estrogen antagonist on mammary gland and uterine tissue.

ER:5.7 nM

Raloxifene significantly differs from estrogen due to its lack of substantial estrogenic effects on uterine tissues. In rat femurs, Raloxifene rebuilds bone mineral density and the expression of TGF beta 3 mRNA. Oral administration of 0.1 mg/kg to 10 mg/kg of Raloxifene for 5 weeks increases the density of femurs and tibias in ovariectomized rats. With an ED50 of 0.2 mg/kg, Raloxifene reduces serum cholesterol levels in ovariectomized (OVX) rats. In ovariectomized rats, Raloxifene blocks the deterioration of bone quality and growth changes, bone remodeling, and serum cholesterol content, albeit with lesser effects on reducing bone formation and unable to prevent uterine atrophy.

Raloxifene is a non-competitive inhibitor of aldehyde oxidase (with a Ki of 51 nM), targeting the enzyme's reduction reaction of compounds containing isohydroxystearic acid. It has been proven to effectively inhibit the human liver aldehyde oxidase-catalyzed oxidation of phthalazine, vanillin, and nicotine-δ1' (5')- iminium with Ki values of 0.87 nM, 1.2 nM, and 1.4 nM, respectively. Additionally, Raloxifene acts as a full agonist at nanomolar concentrations, activating the TGFβ 3 promoter, and serves as a pure estrogen antagonist in transient transfection assays by inhibiting the expression of vitellogenin promoter with estrogen response elements.