An Orally Effective Mammalian Antifertility Agent

Summary U-11555A, a derivative of 2,3-diphenylindene, is an orally active antifertility agent in laboratory mammals. In rats, its efficacy is limited to the period of tubal transport of the zygote. Single oral doses, administered any time within 4 days of breeding, effectively inhibit pregnancy. After the zygote has reached the uterus U-11555A is ineffective as a pregnancy inhibitor. At effective antifertility dosages, U-11555A does not exhibit significant progestational, antiprogestational, antigonadotropic, androgenic, or estrogenic activities. U-11555A inhibits the uterine and vaginal response to endogenous and exogenous estrogens.