HyNic-PEG-Mal is a functionalized polymer that is widely used in pharmaceutical research and development. The polymer consists of a hydrazinonicotinamide (HyNic) group, a polyethylene glycol (PEG) linker, and a maleimide (Mal) group. HyNic is a bioorthogonal reactive group that can specifically bind to a complementary functional group such as DBCO or BCN. PEG is a hydrophilic linker that can increase the solubility and bioavailability of drugs. Mal is a thiol-reactive group that can covalently bind to cysteine residues in proteins or peptides. The introduction of these functional groups into HyNic-PEG-Mal enables the conjugation of drugs or therapeutic agents to biomolecules for targeted delivery, imaging, or therapy. Moreover, HyNic-PEG-Mal can also be used as a tool for site-specific labeling, protein crosslinking, or bioconjugation.