In spite of language in the labeling for ospemifene, the preclinical and clinical data seems to support the fact that it is 1) no more estrogenic in the endometrium than the well studied raloxifene 2) an estrogen antagonist
in the breast; and 3) estrogenic in the venous system (in spite of low rates of VTE in the clinical trials to date).
Antiestrogens 2 Structure- activity studies in a series of 3- aroyl- 2- arylbenzo [b]thiophene derivatives leading to [6hydroxy- 2- (4-hydroxyphenyl)benzo[b] thien- 3- yl][4- [2- (1- piperidinyl)ethoxy] phenyl]methanone hydrochloride(LY156758), a remarkable effective estrogen antagonist
with only minimal intrinsic estrogenicity.
Tamoxifen, for example, is an estrogen antagonist
for the breast, exhibiting a cytostatic effect on ER-positive breast cancer cells, slowing proliferation.
The AF-2 mutation in the E/F domain disrupts AF-2 but can be activated via the AF-1 function by the estrogen antagonist
ICI 182,780 (ICI) (Arao et al.
It is thought to have a weak estrogenlike effect, as well as estrogen antagonist
This estrogen-elicited event is not abrogated by the estrogen antagonist
, ICI 182, 780, confirming its independence from the presence of estrogen receptor a (Lareef et al.
The estrogenic activities of all compounds could be completely suppressed by the pure estrogen antagonist
, ICI 182,780, suggesting that the compounds exert their activities through ER.
Tamoxifen, a nonsteroidal estrogen antagonist
, is the endocrine treatment of choice to prevent breast cancer recurrence in women with positive estrogen receptors.
A complete estrogen antagonist
in the uterus, raloxifene was initially put on the shelf after a phase II trial showed that it caused no response in women with metastatic breast cancer refractory to tamoxifen, he said.
1) Others, citing more recent research, have identified tamoxifen as an estrogen antagonist
, that is, a chemical which directly interferes with estrogen itself.
SERMs or "smart estrogens" behave as a complete estrogen antagonist
in the uterus and breast tissue and as an estrogen agonist on bone and lipid metabolism.
2) It acts as estrogen antagonist
in the uterus and breast.