Figure 2.

Steroid synthesis pathway and aromatization. Abiraterone is a novel cytochrome P450 (CYP)17 inhibitor that irreversibly inhibits the generation of adrenal steroids downstream of CYP17. It suppresses the generation of both androgens and estrogens. Flutamide competes with testosterone for androgen receptors (ARs), preventing their activation. Tamoxifen is an antagonist of the estrogen receptor (ER), blocking its downstream signaling. Anastrozole and letrozole block the production of estrogens by inhibiting the enzyme aromatase.