Abstract: The present invention is related to heparin-like compounds characterized by their capacity of inhibiting collagen-induced platelet aggregation in flowing whole blood and their use for prophylactic treatment of arterial thrombosis associated with vascular or microvascular injury and interventions. Said properties are related to a high coupling density of negatively charged heparin or heparin-like glycosaminoglycan molecules, present in multiple heparin or heparin-like glycosaminoglycans as well as in proteoglycans containing said multiple heparin or heparin-like glycosaminoglycans or lower-molecular-weight heparin or heparin-like glycosaminoglycans connected directly or through spacer/linker molecules to globular core molecules. Heparin-like compounds, with said properties are obtainable from mammalian mast cells, by tissue extraction or cell cultivation.