Фулвестрант

Fulvestrant was launched in the US as a novel once monthly injectable steroidal estrogen antagonist for the treatment of hormone receptor positive metastatic breast cancer in postmenopausal women with disease progression following estrogen therapy. This 7a-alkylsulphinyl derivative of estradiol can be prepared in 10 steps from 6,7- didehydro-19-nor-testosterone by successive conjugate addition of the organocuprate derived from O-protected 9-bromononan-l-o1 followed by aromatization of the resulting enone, then activation of the protected primary alcohol, substitution with 4,4,5,5,5- pentafluoropentanthiol and oxidation to the sulfoxide. Fulvestrant is the first “pure” estrogen antagonist from a novel class known as selective estrogen receptor down regulators (SERDs). It binds to the estrogen receptor (ER), with affinity close to that of estradiol and 100 fold greater than that of tamoxifen (a partial estrogen antagonist), preventing estrogen-stimulated gene activation, thereby interfering with the estrogenrelated processes essential for cell-cycle completion. Fulvestrant also appears to downregulate the ER by 80-90% often to non detectable level both in vitro and in vivo. In comparison to tamoxifen, fulvestrant is devoid of systemic estrogenic activity, it displays no uterotrophic activity and is able to block the uterine stimulation of estradiol or tamoxifen. Furthermore, fulvestrant completely blocks the cell growth in tamoxifen-resistant breast cancer cell-lines and prevents growth of tamoxifen resistant tumor in mice. In clinical trials, it was also shown that fulvestrant is comparable to anastrozole (a third generation aromatase inhibitor) both in efficacy and tolerability in postmenopausal women with tamoxifen-resistant advanced breast cancers.

White or almost white powder.

A novel steroidal estrogen antagonist reported to lack any partial agonist activity. Antineoplastic (hormonal).

ChEBI: A 3-hydroxy steroid that is 17beta-estradiol in which the 7alpha hydrogen has been replaced by a nonyl group in which one of the hydrogens of the terminal methyl has been replaced by a (4,4,5,5,5-pentafluoropentyl)sulfinyl group. An estrogen receptor antagonist, it is used in the treatment of breast cancer.

Fulvestrant, 7α-[9-[(4,4,5,5,5-pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17β-diol (Faslodex), is an antagonist structurally based onthe estradiol structure, with a long, substituted alkyl chainattached at the 7α-position of the steroid skeleton. Whenbound to the ERs, this alkyl chain induces a conformationof the receptor distinctive from that formed upon estradiolor tamoxifen binding, preventing agonist action.Fulvestrant is a pure antagonist at both ER_αand ER_βandan ER downregulator (stimulates degradation of the ER),completely lacking the agonist activity that is seen with tamoxifenor raloxifene. The different pharmacological profileof fulvestrant allows the use of this agent in womenwho have had disease progression after prior antiestrogentherapy (typically tamoxifen), providing an alternative toaromatase inhibitors.

A high affinity estrogen receptor antagonist (IC 50 = 0.29 nM), devoid of any partial agonism both in vitro and in vivo . Also high affinity agonist at the membrane estrogen receptor GPR30.

Side effects appear to be minimal and include several GI symptoms , headache, and hot flashes . There is no clinical evidence of uterine stimulation or laboratory evidence of stimulation of endometrial carcinoma models. Fulvestrant should not be adm inistered to women who are pregnant, who are taking antic oagulants, or who have thrombocytopenia.