1-CARBAMOYLALKYL-2-PHENYLINDOLES - RELATIONSHIP BETWEEN SIDE-CHAIN STRUCTURE AND ESTROGEN ANTAGONISM

The 2-phenylindole system has proved to be a versatile structure for t he design of potent antiestrogens, especially when functional groups h ave been introduced into the alkyl side chain in position 1. In analog y to steroidal structures such as ICI 164,384 a number of 2-phenylindo les with carbamoylalkyl and aminoalkyl side chains were synthesized. T hey bind to the calf uterine estrogen receptor with relative binding a ffinities between 2.1 and 21 (estradiol = 100). The antiestrogenic eff ect of these compounds was demonstrated by the inhibition of transcrip tional activity which was measured in a new luciferase assay with the EREwte luc as reporter plasmid. The derivative with a methyl-n-propyld odecanamide side chain (4h) antagonized the effect of estradiol (10(-9 ) M) completely at concentrations of 10(-7) M and higher. As a sensiti ve model for quantification of estrogenic and antiestrogenic effects i n vitro we used HeLa-cells cotransfected both with the reporter plasmi d and estrogen receptor expression vectors HEG0 and HE0. In cells tran sfected with these vectors transcriptional activity was strongly depen dent on side chain structure. With mutated receptors we were able to s how that this activity was mainly due to TAF-1 whereas TAF-2 remained silent. When we studied the effect of some of the new compounds in viv o using the mouse uterine weight assay, we observed a correlation betw een transcriptional activity in transfected HeLa cells and estrogenic effects in mice. Two of the 1-carbamoylalkyl-2-phenylindoles (4f, 4h) proved to be ''pure'' antiestrogens both in vitro and in vivo. In estr ogen-sensitive MCF-7 breast cancer cells, they strongly inhibit cellul ar growth. Some of the IC50-values were close to 10(-8) M.