Integrin αIIbβ3 inhibitor preserves microvascular patency in experimental acute focal cerebral ischemia

Background and Purpose-Platelets become activated and accumulate in brain microvessels of the ischemic microvascular bed after experimental focal cerebral ischemia. The binding of glycoprotein IIb/IIIa (integrin alpha(IIb)beta(3)) on platelets to fibrinogen is the terminal step in platelet adhesion and aggregation. This study tests the hypothesis that inhibition of platelet-fibrin(ogen) interactions may prevent microvascular occlusion after experimental middle cerebral artery occlusion (MCA:O). Methods-TP9201 is a novel Arg-Gly-Asp (RGD)-containing integrin alpha(IIb)beta(3) inhibitor. Microvascular patency after 3-hour MCA:O and I-hour reperfusion within the ischemic and nonischemic basal ganglia was compared in adolescent male baboons who received high-dose TP9201 (group A: IC80 in heparin, n=4), low-dose TP9201 (group B: IC30 in heparin, n=4), or no treatment (group C: n=4) before MCA:O, Results-After MCA:O, microvascular patency decreased significantly in group C. However, in the ischemic zones of groups A and B compared with group C, patencies were significantly greater in the 4.0- to 7.5-mu m-diameter (capillary) and 7.5- to 30.0-mu m-diameter vessels (2P<0.05), A dose-dependent increase in hemorrhagic transformation was seen in group A (3 of 4 animals) compared with group B (1 of 4 animals), and no hemorrhage was visible in group C (chi(2) analysis for trend, P<0.05). Conclusions-Platelet activation contributes significantly to ischemic microvascular occlusion. Occlusion formation may be prevented by this RGD-integrin alpha(IIb)beta(3) inhibitor at a dose that does not produce clinically significant parenchymal hemorrhage. The effect of microvascular patency on neuron recovery can now be tested.