Fulvestrant-d3 (Synonyms: ICI 182780-d3; ZD 9238-d3; ZM 182780-d3)

Fulvestrant-d3 is intended for use as an internal standard for the quantification of fulvestrant by GC- or LC-MS. Fulvestrant is a selective estrogen receptor degrader (SERD) that downregulates and degrades estrogen receptor α (ERα). It binds to rat uterine ER with an IC50 value of 44.8 nM and prevents uterine weight increases induced by estradiol in immature rats (ED50 = 0.06 mg/kg per day) but has no effect on uterine weight alone. It also decreases uterine weight in adult rats without affecting the production of luteinizing and follicle-stimulating hormones and prolactin. Fulvestrant inhibits the growth of ER-positive MCF-7 human breast cancer cells but not ER-negative BT-20 cells when used at a concentration of 1 µg/ml. It also prevents tumor growth in MCF-7 and Br10 breast cancer mouse xenograft models when used at a single dose of 5 mg per animal. Fulvestrant is neuroprotective in vitro against neurotoxicity induced by glutamate- and amyloid-β (1-42) (Aβ42) in primary rat hippocampal cells. Formulations containing fulvestrant have been used in the treatment of estrogen-sensitive breast cancer.