Prodrugs of steroidal C-17 benzoazoles, pyrimidinoazoles (az-abenzoazoles) and diazines. Methods of synthesis are also described, whereby a prodrug group is substituted for a functional group at A ring portion of the ABC ring structure of the steroid. Suitable pro-drug groups include amino acid groups, succinate groups, phosphate groups, or sulfamate groups. The prodrugs of the disclosed compounds allow for improved oral bioavailability of the compounds that are inhibitors of human CYP 17 enzyme as well as potent antagonists of both wild type and mutant androgen receptors (AR). The compounds and the corresponding prodrugs are useful for the treatment of conditions such as human prostate cancer, breast cancer, and prostate hyperplasia.
