PROTAC degraders BET proteins Brd2, Brd3 and Brd4 General MZ1 BET PROTAC degrader General MZP-54 BET PROTAC degrader General MZP-55 BET PROTAC degrader General AT1 Brd4 PROTAC degrader E3 ubiquitin ligase VHL General CM11 VHL Homo-PROTAC degrader Brd 7/9