Brilanestrant (GDC-0810, ARN-810） is a potent ER-α binder (ER-α, IC50 = 6.1 nM; ER-β, IC50 = 8.8 nM), a full transcriptional antagonist with no agonism and displays good potency and efficacy in ER-α degradation (EC50 = 0.7 nM) and MCF-7 breast cancer cell viability (IC50 = 2.5 nM) assays with good selectivity over other nuclear hormone receptors.