PROSTVAC, a poxvirus-based active immunotherapy targeting the prostate-specific antigen (PSA), resulted in an 8.5-month increase in the mOS (25.1 vs. 16.6 months, p = 0.0061) in a randomized, placebo-controlled Phase 2 clinical trial of men with asymptomatic or minimally symptomatic castration-resistant metastatic prostate cancer (mCRPC) [3]. Here, KLK3 is linked to metastatic prostate carcinoma.