formestane

Formestane is a synthetic steroidal aromatase inhibitor used primarily in the treatment of estrogen receptor-positive breast cancer in postmenopausal women. It acts as a type I (steroidal), second-generation irreversible inhibitor of the aromatase enzyme (estrogen synthetase), which is responsible for converting androgens to estrogens. By inhibiting this enzyme, formestane significantly reduces estrogen levels in the body and thereby suppresses the growth of hormone-sensitive breast cancer cells. Formestane was one of the first selective aromatase inhibitors developed for clinical use and was marketed under brand names such as Lentaron. Due to poor oral bioavailability, it is administered via intramuscular injection every two weeks. With the advent of newer and more effective aromatase inhibitors with better administration profiles (e.g., oral agents), formestane has largely been discontinued or restricted to limited markets[3][4][5][6]. Common side effects include hot flashes, joint pain, fatigue, mood changes, decreased bone mineral density (risk of osteoporosis), local injection site reactions and other hormonal effects[4][5]. Formestane also acts as a prohormone to 4-hydroxytestosterone[1].

Brand names

Lentaron

Other names

4-hydroxyandrostenedione