Mechanisms of heparanase inhibition by the heparan sulfate mimetic PG545 and three structural analogues

• Clinical candidate PG545 inhibits heparanase with parabolic competitive kinetics.
• Analogues of this compound show different modes of heparanase inhibition.
• The cholestanol aglycon of PG545 increases affinity for heparanase.
• Tetrasaccharides have higher affinity for heparanase than trisaccharides.
• A schematic model of inhibition by PG545 and analogues is proposed.

The tetrasaccharide heparan sulfate (HS) mimetic PG545, a clinical anti-cancer candidate, is an inhibitor of the HS-degrading enzyme heparanase. The kinetics of heparanase inhibition by PG545 and three structural analogues were investigated to understand their modes of inhibition. The cholestanol aglycon of PG545 significantly increased affinity for heparanase and also modified the inhibition mode. For the tetrasaccharides, competitive inhibition was modified to parabolic competition by the addition of the cholestanol aglycon. For the trisaccharides, partial competitive inhibition was modified to parabolic competition. A schematic model to explain these findings is presented.

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