Conformationally constrained sialyl analogues as new potential binders of h-CD22

: Here, two conformationally constrained sialyl analogues were synthesized and characterized in their interaction with the inhibitory Siglec, human CD22 (h-CD22). An orthogonal approach, including biophysical assays (SPR and fluorescence), ligand-based NMR techniques, and molecular modelling, was employed to disentangle the interaction mechanisms at a molecular level. The results showed that the Sialyl-TnThr antigen analogue represents a promising scaffold for the design of novel h-CD22 inhibitors. Our findings also suggested that the introduction of a biphenyl moiety at position 9 of the sialic acid hampers the canonical accommodation of the ligand in the protein binding pocket, even though the affinity with respect to the natural ligand is increased. Our outcomes address the search of novel modifications of the Neu5Ac-a(2-6)-Gal epitope, outlining new hints for the design and synthesis of high-affinity h-CD22 ligands, offering new prospects for therapeutic intervention to prevent autoimmune diseases and B-cells malignancies.