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A potent specific pure antiestrogen with clinical potential
A E Wakeling1, M Dukes, J Bowler
1ICI Pharmaceuticals, Macclesfield, Cheshire, United Kingdom.
Cancer Research
|August 1, 1991
Summary
A new pure antiestrogen, ICI 182,780, shows significantly greater potency than ICI 164,384 in inhibiting estrogen receptor activity and breast cancer cell growth. This compound demonstrates sustained antiestrogenic effects and potent in vivo antitumor activity, making it a promising candidate for breast cancer therapy.
Area of Science:
- Endocrinology
- Pharmacology
- Oncology
Background:
- Previous research developed 7 alpha-alkylamide analogues of estradiol with pure antiestrogenic activity, such as ICI 164,384.
- Estrogen receptor antagonists are crucial in treating endocrine-responsive breast cancer.
Purpose of the Study:
- To identify and characterize a novel compound, ICI 182,780, with enhanced pure antiestrogenic potency and antagonist activity.
- To evaluate the in vitro and in vivo efficacy of ICI 182,780 as a potential breast cancer therapeutic.
Main Methods:
- Compared the antiuterotrophic potency of ICI 182,780 and ICI 164,384 in immature rats.
- Assessed relative binding affinities at the estrogen receptor and in vitro growth-inhibitory effects on MCF-7 human breast cancer cells.
- Evaluated sustained antiestrogenic effects in rats and monkeys, and in vivo antitumor activity in nude mice xenografts.
Main Results:
- ICI 182,780 exhibited over 10-fold greater antiuterotrophic potency than ICI 164,384 in vivo.
- ICI 182,780 showed higher relative binding affinity (0.89 vs. 0.19) and superior in vitro growth inhibition of MCF-7 cells (0.29 nM vs. 1.3 nM) compared to ICI 164,384.
- ICI 182,780 demonstrated superior efficacy to 4'-hydroxytamoxifen in inhibiting MCF-7 growth and DNA synthesis, with sustained effects and significant in vivo antitumor activity.
Conclusions:
- ICI 182,780 is a potent pure antiestrogen with significantly enhanced efficacy compared to existing compounds.
- Its sustained antiestrogenic effects and strong in vivo antitumor activity position it as a key candidate for evaluating complete estrogen withdrawal in breast cancer treatment.