Anastrozole
Anastrozole is a nonsteroidal inhibitor of estrogen synthesis that resembles paclitaxel in chemical structure.  As a third-generation aromatase inhibitor, anastrozole selectively binds to and reversibly inhibits aromatase, a cytochrome P-450 enzyme complex found in many tissues including those of the premenopausal ovary, liver, and breast; aromatase catalyzes the aromatization of androstenedione and testosterone into estrone and estradiol, the final step in estrogen biosynthesis.  In estrogen-dependent breast cancers, ananstrozole may inhibit tumor growth. (NCI04)