Steroidal aromatase inhibitors are a class of drugs that are mostly used for treating breast cancer in postmenopausal women. High levels of estrogen in breast tissue increases the risk of developing breast cancer and the enzyme aromatase is considered to be a good therapeutic target when treating breast cancer due to it being involved in the final step of estrogen biosynthetic pathway and also its inhibition will not affect production of other steroids. Aromatase Inhibitors are classified into two categories based on their structure, nonsteroidal and steroidal; the latter resemble the structure of androstenedione.[1] Steroidal aromatase inhibitors irreversibly inhibit the enzyme by binding covalently to the binding site of aromatase so the substrate cannot access it.[2]
Vanasten was invoked but never defined (see the help page).