Amine PEG Acetic Acid (NH2-PEG-COOH) is a linear heterofunctional PEG reagent with one amino group and one carboxyl group at each end of the molecular chain. Primary amines readily react with NHS esters, carboxylic acids and many other functional groups. The active group at the end of the product can be connected to some modified peptides, proteins, carbohydrates, folic acid or antibodies, etc., so that it has an active targeting effect. The PEG moiety in the heterobifunctional PEG derivatives provides water solubility, biocompatibility, and flexibility. Applications are particularly suitable for the development of antibody drug conjugates (ADCs).