ESR1 and breast cancer: Within this series of tris-benzamides, one compound (ERX-11) with a hydroxyethyl functional group mimicking a serine residue (Figure 1A) was consistently able to block 17-β-estradiol (E2)-induced proliferation in 8/8 ER-positive breast cancer cell lines (Figure 1B, Figure 1—figure supplements 1C, D and 2B), with an IC50, ranging from 250 to 500 nM.