Used in bioconjugation for creating stable linkages between proteins, antibodies, or peptides and other molecules such as drugs, labels, or solid supports. Its primary application is in the development of antibody-drug conjugates (ADCs), where it enables controlled attachment through thiol-disulfide exchange. The pyridyldithio group reacts selectively with free thiols, while the NHS ester end binds to primary amines on target biomolecules. This bifunctional reactivity allows for site-specific conjugation with measurable release kinetics due to the disulfide bond's sensitivity to reducing environments. Commonly used in diagnostic assays, targeted therapies, and protein labeling workflows where controlled, reversible linkage is required.