In a first approach, structural determinants for recognition by, and inhibition of, heparanase are being identified by combined molecular modeling, biochemical, NMR, X-ray crystallographic, and biological studies. The biochemical study is addressed to elucidate the minimal saccharide sequence that can serve as a substrate for heparanase. Targets for oligosaccharide synthesis are defined on the basis of structure-activity correlations emerging from binding and inhibition studies with natural, synthetic and semi-synthetic oligosaccharides and polysaccharides. Oligosaccharides in which the bond cleavable by heparanase has been made resistant to the enzyme by mimicking the critical glycosidic bonds and/or by placing suitable substituents near the cleavable bond will be then synthesized.
In a second, convergent approach, heparanase inhibitors will be obtained. Sulfated polysaccharides with systematically different carbohydrate backbones, selected on the basis of preliminary molecular modeling studies are being modified regiospecifically so as to modulate their sulfation and N-acetylation patterns and to remove sulfate groups not necessarily involved in enzyme recognition and inhibition. All products are screened for their heparanase-inhibiting activity. Active products will be tested in vivo models, some of which using novel methods for testing growth inhibition of tumors produced by heparanase-secreting cells.