Used in bioconjugation processes, particularly for linking antibodies to cytotoxic agents in antibody-drug conjugates (ADCs). Its key function is to provide a stable linkage between the targeting antibody and the drug payload, while allowing controlled release of the drug inside target cells. The 2-pyridyldithio group enables reversible disulfide bonding, facilitating intracellular drug release in reducing environments like the cytoplasm. The NHS ester (succinimidyloxycarbonyl) group reacts efficiently with primary amines on proteins, making it suitable for selective and efficient conjugation under mild conditions. Widely applied in the development of targeted cancer therapies where precise drug delivery is critical.