Peptide linkers are a class of protease cleavable linkers. Peptide Linkers are developed as the critical component of antibody drug conjugate (ADC) which play vital roles in the overall success of the ADC drug due to their superior plasma stability and controlled payload release mechanism. A well-designed linker helps the antibody to selectively deliver a cytotoxic drug to tumor cells and accurately releases the drug at tumor site. By introducing a PEG into the linker, it increases the water-solubility and helping fine tune the drug DMPK.