Anastrozole, sold under the brand name Arimidex among others, is an antiestrogenic medication used in addition to other treatments for breast cancer. Specifically it is used for hormone receptor-positive breast cancer. It has also been used to prevent breast cancer in those at high risk. It is taken by mouth.
Clomifene, also known as clomiphene, is a medication used to treat infertility in women who do not ovulate, including those with polycystic ovary syndrome. It is taken by mouth.
Selective estrogen receptor modulators (SERMs), also known as estrogen receptor agonists/antagonists (ERAAs), are a class of drugs that act on estrogen receptors (ERs). Compared to pure ER agonists–antagonists, SERMs are more tissue-specific, allowing them to selectively inhibit or stimulate estrogen-like action in various tissues.
Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and men. It is also being studied for other types of cancer. It has been used for Albright syndrome. Tamoxifen is typically taken daily by mouth for five years for breast cancer.
Fulvestrant, sold under the brand name Faslodex among others, is an antiestrogenic medication used to treat hormone receptor (HR)-positive metastatic breast cancer in postmenopausal women with disease progression as well as HR-positive, HER2-negative advanced breast cancer in combination with abemaciclib or palbociclib in women with disease progression after endocrine therapy. It is given by injection into a muscle.
2-Methoxyestradiol is a natural metabolite of estradiol and 2-hydroxyestradiol (2-OHE2). It is specifically the 2-methyl ether of 2-hydroxyestradiol. 2-Methoxyestradiol prevents the formation of new blood vessels that tumors need in order to grow (angiogenesis), hence it is an angiogenesis inhibitor. It also acts as a vasodilator and induces apoptosis in some cancer cell lines. 2-Methoxyestradiol is derived from estradiol, although it interacts poorly with the estrogen receptors. However, it retains activity as a high-affinity agonist of the G protein-coupled estrogen receptor (GPER).
Raloxifene, sold under the brand name Evista among others, is a medication used to prevent and treat osteoporosis in postmenopausal women and those on glucocorticoids. For osteoporosis it is less preferred than bisphosphonates. It is also used to reduce the risk of breast cancer in those at high risk. It is taken by mouth.
Toremifene, sold under the brand name Fareston among others, is a medication which is used in the treatment of advanced breast cancer in postmenopausal women. It is taken by mouth.
Tibolone, sold under the brand name Livial among others, is a medication which is used in menopausal hormone therapy and in the treatment of postmenopausal osteoporosis and endometriosis. The medication is available alone and is not formulated or used in combination with other medications. It is taken by mouth.
Lasofoxifene, sold under the brand name Fablyn, is a nonsteroidal selective estrogen receptor modulator (SERM) which is marketed by Pfizer in Lithuania and Portugal for the prevention and treatment of osteoporosis and for the treatment of vaginal atrophy, and the result of an exclusive research collaboration with Ligand Pharmaceuticals (LGND). It also appears to have had a statistically significant effect of reducing breast cancer in women according to a study published in The Journal of the National Cancer Institute.
Afimoxifene, also known as 4-hydroxytamoxifen (4-OHT) and by its tentative brand name TamoGel, is a selective estrogen receptor modulator (SERM) of the triphenylethylene group and an active metabolite of tamoxifen. The drug is under development under the tentative brand name TamoGel as a topical gel for the treatment of hyperplasia of the breast. It has completed a phase II clinical trial for cyclical mastalgia, but further studies are required before afimoxifene can be approved for this indication and marketed.
An estrogen ester is an ester of an estrogen, most typically of estradiol but also of other estrogens such as estrone, estriol, and even nonsteroidal estrogens like diethylstilbestrol. Esterification renders estradiol into a prodrug of estradiol with increased resistance to first-pass metabolism, slightly improving its oral bioavailability. In addition, estrogen esters have increased lipophilicity, which results in a longer duration when given by intramuscular or subcutaneous injection due to the formation of a long-lasting local depot in muscle and fat. Conversely, this is not the case with intravenous injection or oral administration. Estrogen esters are rapidly hydrolyzed into their parent estrogen by esterases once they have been released from the depot. Because estradiol esters are prodrugs of estradiol, they are considered to be natural and bioidentical forms of estrogen.
Triphenylethylene (TPE) is a simple aromatic hydrocarbon that possesses weak estrogenic activity. Its estrogenic effects were discovered in 1937. TPE was derived from structural modification of the more potent estrogen diethylstilbestrol, which is a member of the stilbestrol group of nonsteroidal estrogens.
Ethamoxytriphetol is a synthetic nonsteroidal antiestrogen that was studied clinically in the late 1950s and early 1960s but was never marketed. MER-25 was first reported in 1958, and was the first antiestrogen to be discovered. It has been described as "essentially devoid of estrogenic activity" and as having "very low estrogenic activity in all species tested". However, some estrogenic effects in the uterus have been observed, so it is not a pure antiestrogen but is, instead, technically a selective estrogen receptor modulator (SERM). For all intents and purposes, it is a nearly pure antiestrogen, however.
Etacstil is an orally active, nonsteroidal, combined selective estrogen receptor modulator (SERM) and selective estrogen receptor degrader (SERD) that was developed for the treatment of estrogen receptor-positive breast cancer. It was shown to overcome antiestrogen resistance in breast cancer by altering the shape of the estrogen receptor, thus exhibiting SERD properties. Etacstil is a tamoxifen derivative and one of the first drugs to overcome tamoxifen-resistance. It is the predecessor of GW-7604, of which etacstil is a prodrug. This is analogous to the case of tamoxifen being a prodrug of afimoxifene (4-hydroxytamoxifen).
Endoxifen, also known as 4-hydroxy-N-desmethyltamoxifen, is a nonsteroidal selective estrogen receptor modulator (SERM) of the triphenylethylene group as well as a protein kinase C (PKC) inhibitor. It is under development for the treatment of estrogen receptor-positive breast cancer and for the treatment of mania in bipolar disorder. It is taken by mouth.
Droloxifene, also known as 3-hydroxytamoxifen, is a nonsteroidal selective estrogen receptor modulator (SERM) of the triphenylethylene group that was developed originally in Germany and later in Japan for the treatment of breast cancer, osteoporosis in men and postmenopausal women, and cardiovascular disorders but was abandoned and never marketed. It reached phase II and phase III clinical trials for these indications before development was discontinued in 2000. The drug was found to be significantly less effective than tamoxifen in the treatment of breast cancer in two phase III clinical trials.
Norendoxifen, also known as 4-hydroxy-N,N-didesmethyltamoxifen, is a nonsteroidal aromatase inhibitor (AI) of the triphenylethylene group that was never marketed.
N,N-Desmethyltamoxifen is a metabolite of tamoxifen, a selective estrogen receptor modulator (SERM). It is formed from N-desmethyltamoxifen and is an intermediate in the conversion of tamoxifen and N-desmethyltamoxifen into norendoxifen (4-hydroxy-N,N-desmethyltamoxifen), an active metabolite of tamoxifen.
