Galeterone is a selective CYP17 inhibitor and androgen receptor (AR) antagonist with IC50 of 300 nM and 384 nM, respectively, and is a potent inhibitor of human prostate tumor growth. 

Galeterone and abiraterone reduced AR protein and mRNA expression, and antagonized AR-dependent promoter activation induced by androgen. TOK-001, but not abiraterone, is an effective apparent competitor of the radioligand [(3)H]R1881 for binding to the wild type and various mutant AR (W741C, W741L) proteins. TOK-001 is a consistently superior inhibitor than abiraterone of R1881-induced transcriptional activity of both wild type and mutant AR.