Antithrombotic agents: From RGD to peptide mimetics

This review covers the recent advances in the development of highly potent inhibitors of platelet aggregation as potential therapeutic drugs for thrombosis related to cardiovascular and cerebrovascular diseases. The discovery of RGD sequence-directed cell surface receptors (the integrins) has led to extensive research in the development of small RGD containing peptides and their mimetics as antithrombotic agents. These agents work by inhibiting platelet aggregation through competitive blocking of fibrinogen to the platelet surface receptor, GPIIb/IIIa. The pharmacophoric nature of the aspartic acid and arginine side chains of the RGD unit has allowed the development of strategies for rational design, largely based on assumed bioactive RGD conformations and lead optimization. Applications of such strategies, from RGD peptides to peptide hybrids and then to non-peptide mimetics, are described. Also discussed is the important issue of specificity toward GPIIb/IIIa, keeping in view that the RGD unit is a key recognition signal for a variety of cell surface receptors.