Disclosed are fused tricyclic compounds of the following formula I, ##STR00001## or an enantiomer, diastereomer, tautomer or pharmaceutically acceptable salt thereof. The disclosed compounds are useful as inhibitors of 17.beta.-hydroxysteriod dehydrogenase 3 (17.beta.HSD3). Also disclosed are methods of using such compounds in the treatment of hormone sensitive diseases such as prostate cancer and pharmaceutical compositions comprising such compounds.