EXEMESTANE 25

Exemestane is a steroidal, irreversible aromatase inhibitor used in the treatment of hormone receptor-positive breast cancer in postmenopausal women. It works by permanently binding to and inactivating the aromatase enzyme, thereby suppressing the peripheral conversion of androgens (androstenedione and testosterone) into estrogens. This leads to a marked reduction in circulating estrogen levels, depriving estrogen-dependent tumors of their growth stimulus. Exemestane is typically administered orally once daily and is used either as adjuvant therapy following tamoxifen or as first-line therapy in advanced or metastatic disease. Unlike non-steroidal aromatase inhibitors (such as anastrozole or letrozole), exemestane has a structure similar to androstenedione and acts as a "suicide inhibitor" due to its irreversible binding. Common side effects include hot flashes, joint pain, fatigue, decreased bone mineral density, and mild androgenic effects (e.g., acne, mild hirsutism).