ChEBI: Exemestane is a 17-oxo steroid that is androsta-1,4-diene-3,17-dione in which the hydrogens at position 6 are replaced by a double bond to a methylene group. A selective inhibitor of the aromatase (oestrogen synthase) system, it is used in the treatment of advanced breast cancer. It has a role as an EC 1.14.14.14 (aromatase) inhibitor, an antineoplastic agent, an environmental contaminant and a xenobiotic. It is a 17-oxo steroid and a 3-oxo-Delta(1),Delta(4)-steroid. It derives from a hydride of an androstane.NCI Thesaurus (NCIt): Exemestane is a synthetic androgen analogue. Exemestane binds irreversibly to and inhibits the enzyme aromatase, thereby blocking the conversion of cholesterol to pregnenolone and the peripheral aromatization of androgenic precursors into estrogens. (NCI04)