The inhibitory effect of 4-chloro-2-(2,6-dichloro-4-hydroxyphenyl)-1-ethyl-6-hydroxyindole (D 15413) on estrogen-dependent mammary tumors.

The antineoplastic activity of 4-chloro-2-(2,6-dichloro-4-hydroxyphenyl)-1-ethyl-6-hydroxyindole (D 15413) was determined in several estrogen-dependent mammary tumor models. The growth of DMBA-induced rat mammary carcinomas was inhibited by doses ranging from 2 to 18 mg/kg. A dose of 6 X 12 mg/kg per week p.o. reduced the tumor area by 82% (control + 192%). D 15413 was also active against MNU-induced rat mammary tumors and transplanted MXT tumors of the mouse. In vitro, the growth of estrogen receptor positive MCF-7 breast cancer cells was inhibited by D 15413 (10(-8) - 10(-5) M). A mode of action considering endocrine and cytotoxic effects is discussed.