We have preliminary data for a small molecule glyco-decoy that specifically side-tracks the biosynthesis of the ligand for E-selection, and is a candidate for a novel anti-inflammatory. The three members E, L and P of the selection family are inflammatory adhesion molecules expressed constitutively on the surface of blood leukocytes and on activated endothelial cells and platelets. Discoveries of glycans sialyl LeX and sialyl Lea as mucin glycoprotein ligands for the selection family of cell adhesion proteins has stirred immense interest in pursuit of small molecules for treatment of inflammatory, vascular and cancer diseases. The underlying premise is that controlling the rate of leukocyte adhesion by antagonizing selectin-ligand interactions can lead to new therapies to combat these diseases. GlycoMimetics, Inc., has licensed a selectin ligand derivative to Pfizer in 2011 for $340M with the first indication sickle cell inflammation, as an example of the newly perceived commercial value in this area. We took a different approach, focusing on specificities of sets of enzymes that construct the native ligands. Among PSGL1, E selection and L selection, the latter is known to bind sulfated mucin-glycans. Our findings led to the discovery of sulfo-LeX, sulfo-Lea and various core 2 (Galss3 [Galss4GlcNAcss6]GalNAc?) glycans as the ligands for these cell adhesion proteins. In another approach, we focused on synthesis of modified analogs of monosaccharides such as 4-fluoro-GlcNAc acetates and 4-fluoro-GalNAc acetates as cell-penetrating metabolic inhibitors of the selection ligand assembly enzymes. We also synthesized small molecules as glyco-decoys to disrupt biosynthesis of natural ligands of these selections. A small synthetic glyco-decoy competes with the natural acceptor-substrate and thus diverts the synthesis of the glycan chains from endogenous glycoproteins and glycolipids to soluble ligands, which act as inhibitors of selection binding to cell-bound ligand. Secondarily, ligand absence on cell-bound molecules in the presence of the glyco-decoy precludes adhesion events that begin the inflammatory process. The underlying theme of this strategy is that biosynthetic knowledge about specificity of key enzymes as "hits" is a compelling requirement for developing small molecules for therapeutic discoveries based on inhibiting selection adhesion systems. We have examined specificity of enzyme assembly of N-glycan ligands for E selections. Preliminarily, we have discovered a novel compound that disrupts the biosynthesis of glycans for E selections (patent submitted). In Phase I, the prime objective is to synthesize analogs and related compounds and test as inhibitors of E selection ligand biosynthesis in HL60 cells. CD44 is endowed with a ligand for E selection, and also has a specific receptor for hyaluronic acid, promoting migration in normal cells. CD44 is highly expressed in various cancer cells. A small molecule inhibiting biosynthesis of E selection-specific N-glycans such as in CD44 brings new potential tools for mitigation of inflammatory disorders and adhesion events in cancer. This Phase I proposal meets the central tenet of the SBIR program for promising commercial products.
In our work on biosynthesis of glycans and the assembly enzyme specificities, we have found a small molecule glyco-decoy that specifically disrupts ligand synthesis for E selectin. This preliminary result foretells a whole potential set o compounds and derivatives as drugs that are cell-penetrating and can side-track biosynthetic pathways leading to inflammatory cell adhesion ligands. This has a potential application in many inflammatory diseases including cardiovascular, arthritic and cancer where adhesion molecules can play a role in migration and metastasis.