Arimidex®: A potent and selective fourth-generation aromatase inhibitor

Arimidex® is a potent and selective aromatase inhibitor undergoing evaluation as a treatment for postmenopausal women with advanced breast cancer. Studies to determine the pharmacology of Arimidex were conducted in both animals and humans. In animals, Arimidex was selective for the aromatase enzyme, elicited maximal activity at about 0.1 mg/kg, did not interfere with steroid hormones produced by the adrenal glands, and, at a dose of 1 mg/kg, had no detectable pharmacologic activity other than aromatase inhibition. Absorption of ZD1033, the active component of Arimidex, was rapid and virtually complete after oral administration to animals. ZD1033 was extensively metabolized in animals after oral administration; the metabolites were excreted predominantly in urine.