Emmanuel Antonarakis, MBBCh, of Sidney Kimmel Comprehensive Cancer Center, Baltimore, MD, speaks at the 2019 Genitourinary Cancers Symposium, held in San Francisco, CA. Dr Antonarakis discusses a recent publication by his group on the need for a new molecular taxonomy to predict immune checkpoint inhibitor sensitivity in prostate cancer, highlighting three potential molecular biomarkers for PD-1 inhibitor response.