text: Atamestane (developmental code name SH-489), also known as metandroden, as well as 1-methylandrosta-1,4-diene-3,17-dione, is a steroidal aromatase inhibitor that was studied in the treatment of cancer. It blocks the production of estrogen in the body. The drug is selective, competitive, and irreversible in its inhibition of aromatase.