(2-Pyridyldithio)-PEG1-hydrazine is a one-unit cleavable polyethylene glycol (PEG) linker specifically designed for the synthesis of antibody-drug conjugates (ADCs). This linker offers the advantage of controlled release of the drug payload from the ADC construct. It is utilized in the conjugation process between the antibody and the cytotoxic drug, enabling the targeted delivery of the drug to cancer cells. The (2-pyridyldithio) group of this linker provides stability during circulation in the bloodstream, while the hydrazine moiety allows for efficient drug release at the tumor site. Overall, the (2-pyridyldithio)-PEG1-hydrazine linker serves as a valuable tool in the development of targeted chemotherapeutic agents for cancer treatment.