A study has been carried out to verify the effect of Defibrotide on the activity and expression of Heparanase enzyme on myeloma tumor cells (U266) and human microvascular endothelial cells (HMEC). The study has demonstrated that defibrotide can be effectively used for the manufacture of a medicament for the treatment of diseases which are positively affected by the inhibition of Heparanse and/or by the downregulation of Heparanse gene expression, such as diabetes.