Used as a water-soluble heterobifunctional crosslinker in antibody-drug conjugates (ADCs) to enable site-specific conjugation. The sulfo-NHS ester reacts with primary amines on antibodies, while the pyridyl disulfide group couples with thiol-containing payloads via disulfide exchange. Its sulfo group enhances water solubility, reducing aggregation during conjugation processes. Facilitates stable attachment of cytotoxic drugs to antibodies, with intracellular release via disulfide reduction in target cells, improving pharmacokinetics and therapeutic efficacy. Suitable for bioconjugation applications requiring high solubility and stability in aqueous environments.