Clinical trials with ENDX at doses ranging from 20 mg/day to 360 mg/day have demonstrated plasma concentrations ranging from 150 nM to 5 μM, with antitumor activity observed in patients with endocrine resistant breast cancer (including patients with prior progression on AIs, TAM, and fulvestrant) as well as in other tumors that do not express ERα, including TAM resistant desmoid and ovarian cancer12–14. Here, ESR1 is linked to breast cancer.