An α-D-N-acetylgalactosamine (GalNAcα) ligand on a serine residue (Tn antigen, GalNAcα1-O-Ser) equipped with a biotin tag through an amide bond. The biotin moiety binds with high affinity to streptavidin and neutravidin, enabling straightforward immobilization on chips, in wells, or on other streptavidin/neutravidin-coated platforms. This compound enables the construction of hepatocyte-targeted therapeutics and research tools that exploit the asialoglycoprotein receptor (ASGPR), which is highly expressed on liver hepatocytes and binds GalNAc-containing ligands with high affinity. The terminal GalNAcα residue is also a substrate for glycosyltransferases, including galactosyltransferases and sialyltransferases, enabling enzymatic chain extension.