Investigating Glycol-Split-Heparin-Derived Inhibitors of Heparanase: A Study of Synthetic Trisaccharides

Abstract

Heparanase is the only known endoglycosidase able to cleave heparan sulfate. Roneparstat and necuparanib, heparanase inhibitors obtained from heparin and currently being tested in man as a potential drugs against cancer, contain in their structure glycol-split uronic acid moieties probably responsible for their strong inhibitory activity. We describe here the total chemical synthesis of the trisaccharide GlcNS6S-GlcA-1,6anGlcNS (<b>1</b>) and its glycol-split (gs) counterpart GlcNS6S-gsGlcA-1,6anGlcNS (<b>2</b>) from glucose. As expected, in a heparanase inhibition assay, compound <b>2</b> is one order of magnitude more potent than <b>1</b>. Using molecular modeling techniques we have created a 3D model of <b>1</b> and <b>2</b> that has been validated by NOESY NMR experiments. The pure synthetic oligosaccharides have allowed the first in depth study of the conformation of a glycol-split glucuronic acid. Introducing a glycol-split unit in the structure of <b>1</b> increases the conformational flexibility and shortens the distance between the two glucosamine motives, thus promoting interaction with heparanase. However, comparing the relative activities of <b>2</b> and roneparstat, we can conclude that the glycol-split motive is not the only determinant of the strong inhibitory effect of roneparstat.