Antagonists estrogen receptor

EM-800 is a pure estrogen receptor antagonist that has recently been used clinically for breast cancer patients who have failed tamoxifen therapy. 

Toremifene is an estrogen receptor antagonist. The pharmacokinetics of toremifene are best described by a two-compartment model, with an a half-life of 4 hours and an elimination half-life of 5 days. Peak plasma concentrations are achieved approximately 3 hours after an oral dose. Toremifene is metabolized extensively, with metabolites found primarily in the feces. Toremifene is used for the treatment of metastatic breast cancer in postmenopausal women with estrogen-receptor-positive or unknown tumors. Toremifene causes hot flashes, vaginal bleeding, thromboembolism, and visual acuity changes. 

Fulvestrant is a pure estrogen receptor antagonist that has been somewhat more effective than those with partial agonist effects in some patients who have become resistant to tamoxifen. ICI 164,384 is a newer antagonist it inhibits dimerization of the occupied estrogen receptor and interferes with its binding to DNA. It has also been used experimentally in breast cancer patients who have become resistant to tamoxifen. 

Assays are expected to detect antiestrogens, but this was not established during the validation process since no estrogen receptor antagonists were tested. 

The antimicrobial napyradiomycins A (192) and B (193) produced by a Streptomyces strain have been shown to be estrogen-receptor antagonists [154]. 

Other evidence for the trophic influences of estrogen comes from what happens when the estrogen s effects are blocked with estrogen receptor antagonists. Tamox-... 

Because raloxifene acts as an estrogen receptor antagonist on some genitourinary tissues, one might expect it to block the vaginal effects of local estrogen therapy. A multicenter placebo-controlled US study in 91 post-meno-pausal women set out to determine whether oral raloxifene (60 mg/day), such as is used to counter post-... 

ICI 164,384, and toremifene. Environmental estrogen receptor antagonists include some phytochemicals (i.e., flavonoids) and PCBs (i.e., 3, 3, 4,4 -tetrachlorobiphenyl). Consequences of estrogen receptor antagonism are typically considered de-feminization (loss of female traits). In laboratory animal studies, estrogen receptor antagonists have been shown in females to disrupt estrous cycles, impair fertility, increase preimplantation loss, and cause embryolethality. 

Y Hori, Y Abe, M Ezaki, T Goto, M Okuhara, M Kohsaka. R1128 substances, novel non-steroidal estrogen-receptor antagonists produced by a Streptomyces. I. Taxonomy, fermentation, isolation, and biological properties. J Antibiot 46 1055-1062, 1993. 

Synonyms ICI 182 780 Trade name Faslodex (AstraZeneca) Indications Metastatic breast cancer Category Estrogen receptor antagonist Half-life —40 days... 

Antiestrogen estrogen receptor antagonist downregulates estrogen receptor protein in human breast cancer cells no estrogen agonist properties... 

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