AbstractHeparanase, a heparan sulfate‐specific endo‐β‐D‐glucuronidase, plays an important role in tumor cell metastasis through the degradation of extracellular matrix heparan sulfate proteoglycans (ECM HSPG). Heparanase activity correlates with the metastatic propensity of tumor cells. Suramin, a polysulfonated naphthylurea, is an inhibitor of heparanase with suramin analogues shown to possess antiangiogenic and antiproliferative properties. We investigated the effects of selected suramin analogues (NF 127, NF 145 and NF 171) on heparanase activity and heparanase‐driven angiogenesis. Studies of the ability of cellular extracts and purified heparanase from human, highly invasive and brain‐metastatic melanoma (70W) cells revealed that heparanase expressed by these cells was effectively inhibited by suramin analogues in a dose‐dependent manner. These analogues possessed more potent heparanase inhibitory activities than suramin: The concentrations required for 50% heparanase inhibition (IC50) were 20–30 μM, or at least 2 times lower than that for suramin. One hundred percent inhibition was observed at concentrations of 100 μM and higher. Of relevance, these compounds significantly decreased (i) the invasive capacity of human 70W cells by chemoinvasion assays performed with filters coated with purified HSPG or Matrigel™, and (ii) blood vessel formation by in vivo angiogenic assays, thus linking their antiangiogenic properties with impedance of heparanase‐induced angiogenesis. Specifically, inhibition of invasion by NF 127, NF 145 and NF 171 was found at 10 μM concentrations of compounds with a significant decrease of invasive values at concentrations as low as 1.5 μM. In addition, NF 127, NF 145 and NF 171 promoted nearly complete inhibition of heparanase‐induced angiogenesis at values ranging from 236 μM (for NF 145) to 362 μM (for NF 127). These results further emphasize the importance of heparanase in invasive and angiogenic mechanisms and the potential clinical application of heparanase inhibitors such as suramin analogues in cancers and angiogenesis‐dependent diseases. © 2003 Wiley‐Liss, Inc.