Thalidomide-O-amido-PEG2-C2-NH2 hydrochloride incorporates an E3 ligase ligand and a linker, can be an immunomodulater for the treatment of cancer.In Vitro: PROTACs contain two different ligands connected by a linker; one is a ligand for an E3 ubiquitin ligase and the other is for the target protein. PROTACs exploit the intracellular ubiquitin-proteasome system to selectively degrade target proteins.