Prodrugs of steroidal CYP17 inhibitors/antiandrogens

Prodrugs of C-17-heterocyclic-steroidal drugs providing improved oral bioavailability and phamacokinetics are described. The drugs are inhibitors of human CYP 17 enzyme, as well as potent antagonists of both wild type and mutant androgen receptors (AR), and are useful for the treatment of urogenital and/or androgen-related cancers, diseases and/or conditions, such as human prostate cancer, breast cancer, and prostate hyperplasia. The disclosure describes methods of synthesizing and using the prodrugs in cancer therapy.