Fulvestrant

Fulvestrant is a selective estrogen receptor degrader (SERD) that downregulates and degrades estrogen receptor α (ERα).^1,2 It binds to rat uterine ER with an IC₅₀ value of 44.8 nM and prevents uterine weight increases induced by estradiol in immature rats (ED₅₀> = 0.06 mg/kg per day) but has no effect on uterine weight alone.³ It also decreases uterine weight in adult rats without affecting the production of luteinizing and follicle-stimulating hormones and prolactin. Fulvestrant inhibits the growth of ER-positive MCF-7 human breast cancer cells but not ER-negative BT-20 cells when used at a concentration of 1 µg/ml. It also prevents tumor growth in MCF-7 and Br10 breast cancer mouse xenograft models when used at a single dose of 5 mg per animal. Fulvestrant is neuroprotective in vitro against neurotoxicity induced by glutamate- and amyloid-β (1-42) (Aβ42) in primary rat hippocampal cells.⁴ Formulations containing fulvestrant have been used in the treatment of estrogen-sensitive breast cancer.

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1. Kansra, S., Yamagata, S., Sneade, L., et al. Differential effects of estrogen receptor antagonists on pituitary lactotroph proliferation and prolactin release. Mol. Cell Endocrinol. 239(1-2), 27-36 (2005).

2. Wardell, S.E., Marks, J.R., and McDonnell, D.P. The turnover of estrogen receptor α by the selective estrogen receptor degrader (SERD) fulvestrant is a saturable process that is not required for antagonist efficacy. Biochem. Pharmacol. 82(2), 122-130 (2011).

3. Wakeling, A.E., Dukes, M., and Bowler, J. A potent specific pure antiestrogen with clinical potential. Cancer Res. 51(15), 3867-3873 (1991).

4. Zhao, L., O'Neill, K., and Brinton, R.D. Estrogenic agonist activity of ICI 182,780 (Faslodex) in hippocampal neurons: Implications for basic science understanding of estrogen signaling and development of estrogen modulators with a dual therapeutic profile. J. Pharmacol. Exp. Ther. 319(3), 1124-1132 (2006).