Tr-PEG2-OH is a PEG-based PROTAC linker utilized in PROTAC synthesis[1]. It also serves as a non-cleavable 2-unit PEG ADC linker for the synthesis of antibody-drug conjugates (ADCs)[2].

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]. ADCs are comprised of an antibody to which is attached an ADC cytotoxin through an ADC linker[2].