Thalidomide-NH-CH2-COOH is the Thalidomide-based cereblon ligand used in the recruitment of CRBN protein. Thalidomide-NH-CH2-COOH can be connected to the ligand for protein by a linker to form PROTACs, such as THAL-SNS-032 [1].
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[1].
[1]. Calla M Olson, et al. Pharmacological perturbation of CDK9 using selective CDK9 inhibition or degradation. Nat Chem Biol. 2018 Feb;14(2):163-170.