Selective estrogenic effects of a novel triphenylethylene compound, FC1271a, on bone, cholesterol level, and reproductive tissues in intact and ovariectomized rats

FC1271a is a novel triphenylethylene compound with a tissue-selective profi le of estrogen agonistic and weak antagonistic effects. It specifically bin ds to the estrogen receptor alpha and beta with affinity closely similar to that of toremifene and tamoxifen. To study the in vivo effects of the comp ound, 4-month-old rats were sham operated (sham) or ovariectomized (OVX) an d treated daily for 4 weeks with various doses of FC1271a or vehicle (orall y). FC1271a was able to oppose OVX-induced bone loss by maintaining the tra becular bone volume of the distal femur. Accordingly, the OVX-induced loss of bone strength was prevented at doses of 1 and 10 mg/kg. FC1271a also pre vented the OVX-induced increase in serum cholesterol in a dose-dependent ma nner. No significant changes in uterine wet weight or morphology were obser ved in the OVX-rats treated with 0.1 or 1 mg/kg FC1271a, but at a dose of 1 0 mg/kg it had a slightly estrogenic effect. In immature rats the effect of FC1271a on uterine wet weight was less stimulatory than that of toremifene or tamoxifen, but more stimulatory than that of raloxifene or droloxifene. The appearance of the dimethylbenzanthracene (DMBA)-induced mammary tumors was inhibited by treatment of DMBA-treated rats with FC1271a in a dose-dep endent manner. In human MCF-7 breast cancer cell tumors raised in nude mice in the presence of estrogen, the growth and expression of pS2 marker gene could not be maintained after estrogen withdrawal by treatment with FC1271a . No formation of DNA adducts was observed in the liver of the FC1871a-trea ted rats. In conclusion, the bone-sparing, antitumor, and cholesterol-lower ing effects of FC1271a combined with a low uterotropic activity and lack of liver toxicity indicate that FC1271a could be an important alternative in planning antiosteoporosis therapy for estrogen deficiency.