Alterations in androgen receptor (AR) signalling are the most prevalent biological events in metastatic castration-resistant prostate cancer (mCRPC) resulting in persistent AR activation. These alterations include AR amplification (amp), mutations, AR splice variants (ARVs), intratumoural androgen biosynthesis and AR enhancer amplification. Enzalutamide and abiraterone acetate are two FDA-approved drugs that target AR signalling in mCRPC. Enzalutamide is an AR antagonist that also blocks AR translocation and function, whereas abiraterone inhibits androgen biosynthesis. A, androgen; ABI, abiraterone; ARm, mutant AR; ENZ, enzalutamide; mut, mutation.