Used as an activated ester in bioconjugation reactions, particularly for the modification of proteins and antibodies. It reacts efficiently with primary amines on biomolecules to form stable amide bonds, enabling the attachment of labels, drugs, or other functional groups. The disulfide linker provides a cleavable bond under reducing conditions, making it useful in the design of antibody-drug conjugates (ADCs) where controlled release of the payload is required. Its nitropyridyl disulfide group allows for thiol-disulfide exchange, facilitating conjugation with cysteine residues or other thiol-containing molecules. Commonly employed in pharmaceutical research and development for targeted therapeutics.