CW-3308 is an orally effective PROTAC that selectively targets BRD9 and is expected to be used to inhibit synovial sarcoma, rhabdomyoma, and other BRD9-dependent human diseases. CW-3308 is composed of PROTAC target protein ligand Naphthyridin-Me-dimethoxybenzene-COOH (red part), Linker 3-Azaspiro[5.5]undecane-9-methanol (black part), E3 ubiquitin ligase ligand Thalidomide-methylpyrrolidine (blue part), where the conjugate of E3 ubiquitin ligase ligand + linker is Thalidomide-pyrrolidine-C-azaspiro.