GP Letrozole (Letrozole) is an oral non-steroidal aromatase inhibitor that has been introduced for the adjuvant treatment of hormonally-responsive breast cancer.
Estrogens are produced by the conversion of androgens through the activity of the aromatase enzyme. Letroplex blocks production of estrogens in this way by competitive, reversible binding to the heme of its cytochrome P450 unit. The action is specific, and Letroplex does not reduce production of mineralo- or corticosteroids. In contrast, the antiestrogenic action of tamoxiplex, the major medical therapy prior to the arrival of aromatase inhibitors, is due to its interfering with the estrogen receptor, rather than inhibiting estrogen production.