Multi-app of Heparin Mimetics Derived from L-Idose

Abstract

Heparan sulfate (HS) is a negatively charged polysaccharide, widely present on the surface of all mammalian cells and in the extracellular matrix. Depending on the sulfation patterns and uronic acid compositions, the HS sequence binds to various proteins, including growth factors, chemokines, and bacterial and viral spike proteins. These interactions play a crucial role in viral and bacterial infections, as well as cancer progression. Despite rapid progress in the synthesis of structurally defined HS oligosaccharides, the direct contribution of uronic acid residues to HS biological functions remains largely unclear. We present a new set of HS mimics that incorporate exclusive L-idose to finely adjust the recognition and activity of growth factors and chemokines. The HS mimics were synthesized using an anhydrous β‐L‐idopyranosyl building block. After exploring various synthetic strategies, we sequentially installed L-idose using a linear approach and regioselectively sulfated to obtain a library of HS mimics. These molecules underwent extensive microarray and conformation studies to unravel the structure-activity relationship with growth factors and chemokines. Furthermore, these molecules proved to be immunogenic, eliciting T-cell dependent immune responses. Mice were immunized with the ID49 ligand, which shares a 67% similarity index with N-unsubstituted heparan sulfate ligands. This immunization procedure resulted in a high-titre IgG antibody response against ID49, also directed against the N-unsubstituted and N-sulfated HS ligands. Further screening for specificity towards sulfation patterns confirmed that the antibody targets 6-O-sulfated and 2-O-sulfated HS N-sulfated ligands. The pharmaceutical potential of these antibodies was demonstrated by selectively staining cancer cells and tissue sections. To better understand how the sulfation pattern, particularly dense vs dispersed sulfation, induces β-amyloid binding, an ITC experiment was conducted with ID49 and a highly sulfated HS hexasaccharide. The densely sulfated ID49 showed similar binding affinity as that of the HS hexasaccharide and reduced the cytotoxicity of β-amyloid aggregates, providing a new insight into the interaction between β-amyloid and HS mimics. Further, we have successfully demonstrated a novel synthetic heparan sulfate-based neoproteoglycan for LYTAC platform that functions independent of antibody conjugation, making it applicable in any environment. Finally, we have discussed the synthesis of amphiphilic carbohydrates to block viral entry. We synthesized a library of amphiphilic heparin mimetics carrying sulfated Oligo-L-idose and Oligo-L-iduronic acid. Among them, sulfated higher oligosaccharides of L-idose with lipophilic aglycones displayed potent anti-SARS-CoV-2 and antiheparanase activity, similar to or better than pixatimod (PG545), and were more potent than their isosteric L-iduronic acid congeners. The findings confirm that fine-tuning higher oligosaccharides, the degree of sulfation, and lipophilic groups can yield compounds with potent anti-SARS-CoV-2 activity. further, we have reported on a library of novel L-idose (Ido)-based HS mimics with a wide range of sulfation patterns designed to replicate many of the functions of native HS oligosaccharides. We employed a linear synthesis strategy to obtain a rare oligo-Idose precursor, utilizing anhydrous β-L-idopyranosyl and Idose thiophenol building blocks. HS mimic microarray binding studies with different growth factors and chemokines showed that selectivity and avidity are greatly modulated by the oligosaccharide length, sulfation code, and Idose conformation. Notably, we have identified highly sulfated HS mimetics as potential ligands for inflammatory chemokines and growth factors. Further investigation into their therapeutic value is ongoing.