(E/Z)-Droloxifene is a mixture of (E)-droloxifene, a selective estrogen receptor modulator (SERM), and (Z)-droloxifene.[1] (E)-Droloxifene binds to the estrogen receptor (ER) in rabbit uterine homogenates (IC50 = 24 nM in a radioligand binding assay), increases uterine weight in immature rats, and reduces estradiol-induced increases in uterine weight in juvenile rats.1,2,3 It also inhibits 17β-estradiol-stimulated growth of MCF-7, ZR-75-1, and T47D human breast cancer cells in a concentration-dependent manner.[4] (Z)-Droloxifene binds weakly to ERs and has no estrogenic or antiestrogenic activity.[5]
References:
[1].Robertson, J.F.R.Selective oestrogen receptor modulators/new antioestrogens: A clinical perspectiveCancer Treat. Rev.30(8)695-706(2004).
[2].Löser, R., Seibel, K., Roos, W., et al.In vivo and in vitro antiestrogenic action of 3-hydroxytamoxifen, tamoxifen and 4-hydroxytamoxifenEur. J. Cancer Clin. Oncol.21(8)985-990(1985).
[3].Hasmann, M., Rattel, B., and Löser, R.Preclinical data for droloxifeneCancer Lett.84(2)101-116(1994).
[4].Kawamura, I., Mizota, T., Lacey, E., et al.The estrogenic and antiestrogenic activities of droloxifene in human breast cancersJpn. J. Pharmacol.63(1)27-34(1993).
[5].Löser, R., Seibel, K., and Huber, H.J.Pharmacological activities of droloxifene isomersAnticancer Res.8(6)1271-1274(1988).