Propargyl-PEG4-Tos is a PEG-based PROTAC linker utilized for the synthesis of PROTACs and cleavable ADC linkers in antibody-drug conjugate (ADC) synthesis [1][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. ADCs are comprised of an antibody to which is attached an ADC cytotoxin through an ADC linker.