Clomiphene analogs with activity in vitro and in vivo against human breast cancer cells

Six hundred triphenylethylenes were assayed for antiproliferative activity against MCF-7, LY2, and MDA-MB-231 breast cancer cells using sulforhodamine B dye to measure proliferation. Here we report on just 63 of the compounds, mostly clomiphene analogs, with substitutions on the alpha' or beta ring, at the vinyl position or in the side chain, of which 23 were active, as defined by antiproliferation IC50 values < or =1 microM. Activity profiles showed that 23 and 11 analogs were active toward MCF-7 and LY2, respectively, but none were active against MDA-MB-231. The IC50 values of tamoxifen were 2.0 microM against MCF-7 and 7.5 microM against LY2 and MDA-MB-231. Estradiol reversed antiproliferative activities of several E isomers but not their Z isomer counterparts. Clomiphene side chain analogs 46 [(E)-1-butanamine, 4-[4-(2-chloro-1,2-diphenylethenyl) phenoxy]-N,N-diethyl-dihydrogen citrate (MDL 103,323)] and 57 [(E)-N-[p-(2-chloro-1,2-diphenylvinyl) phenyl]-N,N-diethylethylenediamine dihydrogen citrate (MDL 101,986)] were 4- to 5-fold more effective than tamoxifen. Methylene additions up to (-CH2-)12 in the clomiphene side chain showed that analog 46 [(-CH2-)4 side chain] had maximal antiproliferative activity, binding affinity, and inhibition of transcription of an estrogen response element luciferase construct in transfected MCF-7 cells. Intraperitoneal administration of 46 or 57 inhibited progression of MCF-7 breast tumor xenografts in nude mice with ED50 values of <0.02 mg/mouse/day. Both analogs may hold promise for treating ER positive breast cancer and are of interest for further development.