Maleimide PEG Hydroxyl (Mal-PEG-OH, HO-PEG-Mal) is a linear heterobifunctional PEG reagent with maleimide and hydroxyl groups. Usually it is used as a crosslinker or spacer between two different chemical entities. Maleimide reacts with thiol, SH, sulfhydryl or sulfhydryl, and hydroxyl can react with carboxylic acid. The PEG moiety in the heterofunctional PEG derivatives provides water solubility, biocompatibility and flexibility. Applications are particularly suitable for the development of antibody drug conjugates (ADCs).Usually it is used as a crosslinker or spacer between two different chemical entities. Maleimide reacts with thiol, SH, sulfhydryl or sulfhydryl, and hydroxyl can react with carboxylic acid. The PEG moiety in the heterofunctional PEG derivatives provides water solubility, biocompatibility and flexibility. Applications are particularly suitable for the development of antibody drug conjugates (ADCs).