Estrogen receptor modulator 6 (compound 3a) is a highly specific and potent agonist of the estrogen receptor (ER) β with a remarkable affinity (K i = 0.44 nM). This compound exhibits an impressive 19-fold selectivity for ERβ over ERα, as evidenced by its affinity (K i = 8.4 nM).
D 15414 is a nonsteroidal weak estrogen of the 2-phenylindole group which was never marketed. It is the major metabolite of the selective estrogen receptor modulator zindoxifene. D-15414 has high affinity for the estrogen receptor and inhibits the growth of ER-positive MCF-7 breast cancer cells in vitro.