Described herein are modified androgen receptor polypeptides that are resistant to inhibition by an androgen receptor inhibitor. Described herein are compositions, combinations, and kits containing the modified androgen receptor polypeptides and methods of using the modified androgen receptor polypeptides. Also described herein are methods of using the modified androgen receptor polypeptides as screening agents for the identification and design of third-generation androgen receptor modulators. Also described herein are third-generation androgen receptor modulators that inhibit the activity of the modified androgen receptor polypeptides. Also described are pharmaceutical compositions and medicaments that include the compounds described herein, as well as methods of using such androgen receptor modulators, alone and in combination with other compounds, for treating diseases or conditions, including cancers, such as castration resistant prostate cancers, that are mediated or dependent upon androgen receptors.