Used in bioconjugation processes to link molecules with high specificity, particularly in the development of antibody-drug conjugates (ADCs). The maleimide group reacts selectively with thiol groups (–SH) on proteins or peptides, enabling stable attachment. The PEG3 spacer improves solubility and reduces aggregation, while also increasing the flexibility and bioavailability of the conjugated compound. Commonly applied in pharmaceutical research and diagnostic reagents where controlled linkage and enhanced pharmacokinetics are required.