Fulvestrant

Fulvestrant is a selective estrogen receptor degrader and downregulator. It binds to estrogen receptors and causes them to be degraded, i.e., broken down into their constituent amino acids.

The medication inhibits estradiol binding in the breast at a much higher level than tamoxifen, is a complete (not partial) ER antagonist due to disrupting AF1 and AF2 sites that fuel breast and breast cancer growth, and also destroys estrogen receptors.