Development of Monoclonal Antibodies that Inhibit Platelet Adhesion or Aggregation as Potential Anti-Thrombotic Drugs

Cardiovascular disease is the major cause of mortality in Western countries. Platelets play a crucial role in the development of arterial thrombosis and other pathophysiologies leading to clinical ischemic events. In the damaged vessel wall, platelets adhere to the subendothelium through an interaction with von Willebrand factor (VWF), which forms a bridge between subendothelial collagen and the platelet receptor glycoprotein (GP) Ib/IX/V. This reversible adhesion allows platelets to roll over the damaged area, decreasing their velocity and resulting in strong platelet activation. This leads to the conformational activation of the platelet GPIIb/IIIa receptor, fibrinogen binding and finally to platelet aggregation. As each interaction (collagen-VWF, VWF-GPIb and GPIIb/IIIa-fibrinogen) plays an essential role in primary haemostasis, loss of either of these interactions results in a bleeding diathesis, implying that interfering with these interactions might result in an anti-thrombotic effect. Whereas GPIIb/IIIa antagonists indeed are effective anti-thrombotics, it has been suggested that drugs which block the initial steps of thrombus formation (collagen-VWF or VWF-GPIb interaction) might have advantages over the ones that merely inhibit platelet aggregation. In this review we will discuss and compare the development of monoclonal antibodies (moAbs) that inhibit platelet adhesion or platelet aggregation. The effect of the moAbs in in vitro experiments, in in vivo models and in clinical trials will be described. Benefits, limitations, current applications and the future perspectives in the development of antibodies for each target will be discussed.