Exemestane

Exemestane is a steroidal agent which causes inactivation of the aromatase enzyme by binding irreversibly to the substrate binding site. Oral exemestane 25 mg/day inactivates peripheral aromatase activity (approximately 98% inactivation) and reduces basal plasma estrone, estradiol and estrone sulphate levels by 85 to 95% in postmenopausal women with advanced breast cancer. Phase II trials indicate that oral exemestane 25 mg/day is an effective second- or third-line agent in the treatment of postmenopausal women with advanced breast cancer (achieving an objective response in up to 28 and 26% of patients, respectively). Results from a phase III trial indicate that exemestane achieves a similar objective response rate to megestrol as a second-line therapy; however, exemestane achieved a significantly longer duration of overall success, time to disease progression and survival time. Exemestane is at least as well tolerated as megestrol, but is associated with significantly fewer bodyweight changes, mainly bodyweight gain (> or = 10%). Other common adverse events are hot flushes, nausea and fatigue.