PROTACBRD4 Degrader-9 (compound 8a) is a novel chemical compound consisting of ligands for von Hippel-Lindau and BRD4, connected by a PROTAC moiety. This compound can effectively degrade the BRD4 protein in PC3 prostate cancer cells. When conjugated with STEAP1 and CLL1 antibodies, PROTACBRD4 Degrader-9 exhibits potent activity, with respective DC50 values of 0.86 nM and 7.6 nM.