Anti-STEAP1 antibody-PROTAC conjugates with a BRD4 ligand and a VHL ligand, particularly STEAP1-5a (drug-to-antibody ratio (DAR) 6.0) (Figure 14), afforded degradation of the BRD4 protein with a DC50 value of 0.67 nM using PC3-S1 prostate cancer cells [49]. Here, STEAP1 is linked to Familial prostate cancer.