Endoxifen Z-isomer hydrochloride (Endoxifen HCl) is the active metabolite of Tamoxifen, which is an effective and selective estrogen receptor antagonist.

ERG (human):1.6 μM

Endoxifen shows anti-estrogenic effects, and decreases the E2-induced PR expression in MCF-7 cells. [1] Endoxifen also blocks ER-alpha transcriptional activity and inhibits estrogen-induced breast cancer cell proliferation. [2] In MCF7, HS 578T, and BT-549 cells, Endoxifen significantly inhibits cell proliferation. [3] Endoxifen also exhibits four-fold higher inhibition on PKC activity compared to tamoxifen. [4] Endoxifen inhibits the hERG current by preferentially interacting with the activated states of cloned hERG potassium channels with IC50 of 1.6 μM. [5]

In vivo, Endoxifen (8 mg/kg, ) inhibits growth of MCF-7 human mammary tumor xenografts in mice, showing more potency than Tamoxifen. [3]

MCF7 and Ishikawa cells are grown in 10% triple charcoal-stripped serum-containing medium for 3 d. The cells are then plated at a density of 2,000 cells per well in 96-well tissue culture plates and treated as indicated every 48 h. Cell proliferation assays are conducted 8 days after the first treatment using a CellTiter-Glo Luminescent Cell Viability kit according to the manufacturer's protocol.(Only for Reference)