Description: Exemestane is a medication used primarily in postmenopausal women. It is a steroidal aromatase inhibitor, meaning it is structurally similar to the natural steroid hormones in the body. It is often used after a patient has already been treated with another medication, such as tamoxifen.

Indication: Exemestane is used to treat:

• Early breast cancer in postmenopausal women who have already been treated with tamoxifen for 2 to 3 years and are switching to Exemestane to complete a total of 5 years of hormonal therapy.
• Advanced or metastatic breast cancer in postmenopausal women whose cancer has progressed despite treatment with tamoxifen.

Mechanism of Action: The main source of estrogen in postmenopausal women is the conversion of androgens (male hormones) into estrogens (female hormones) by an enzyme called aromatase. Many breast cancers are “hormone-sensitive” or “estrogen receptor-positive,” meaning they need estrogen to grow. Exemestane works by binding irreversibly to and inactivating the aromatase enzyme. This is sometimes referred to as “suicide inhibition.” By blocking this enzyme, Exemestane significantly lowers the amount of estrogen in the body, which helps to slow or stop the growth of breast cancer cells.