Thalidomide -4-NH-PEG1-COOH TFA is an E3 Ligase Ligand-Linker Conjugate consisting of Thalidomide and NH-PEG3-NH-Boc. Thalidomide -4-NH-PEG1-COOH TFA acts as a ligand for Cereblon to recruit CRBN protein. Thalidomide -4-NH-PEG1-COOH TFA is a key intermediate in the synthesis of CRBN-based PROTAC molecules.