Suzuki Ken-ichi, Sato Kazuo, Kamohara Masazumi, Kaku Seiji, Kawasaki Tomihisa, Yano Shinya, Iizumi Yuichi
Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co, Ltd, Tsukuba, Ibaraki, Japan.
Biol Pharm Bull. 2002 Aug;25(8):1006-12. doi: 10.1248/bpb.25.1006.
The effects of YM337, the Fab fragment of a humanized anti-glycoprotein IIb/IIIa (GPIIb/IIIa) monoclonal antibody C4G1, on in vitro platelet function and binding properties were compared with those of abciximab, the Fab fragment of the human/murine chimeric anti-GPIIb/IIIa monoclonal antibody 7E3. Both agents completely inhibited platelet aggregation caused by all agonists tested except ristocetin. Further, both inhibited human platelet adhesion to von Willebrand factor, fibrinogen, fibronectin and subendothelial matrix with similar potency. Fibrinogen binding to washed platelets was dose-dependently inhibited by both agents. In binding assay using 125I-YM337 and 125I-abciximab, Kd values determined with platelet-rich plasma were 6.74 +/- 0.56 nM for YM337 and 6.65 +/- 1.45 nM for abciximab, and the number of binding sites were 42,700 +/- 3,000 for YM337 and 76,000 +/- 5,400 for abciximab. GPIIb/IIIa was precipitated from the solubilized fraction of platelets by both agents. In contrast, integrin alphavbeta3 was precipitated from the solubilized fraction of human umbilical vein endothelial cells by abciximab but not by YM337. Fibrinogen binding to purified GPIIb/IIIa was dose-dependently inhibited by both agents. In contrast, vitronectin binding to purified integrin alphavbeta3 was dose-dependently inhibited by abciximab but not by YM337, supporting the idea that abciximab reacts to integrin alphavbeta3. Therefore, YM337 was suggested to bind to a different epitope of GPIIb/IIIa from abciximab. These results suggest that YM337 specifically acts on platelet GPIIb/IIIa receptors and has similar inhibitory properties on platelet aggregation and platelet adhesion to abciximab.
将人源化抗糖蛋白IIb/IIIa（GPIIb/IIIa）单克隆抗体C4G1的Fab片段YM337与鼠/人嵌合抗GPIIb/IIIa单克隆抗体7E3的Fab片段阿昔单抗对体外血小板功能和结合特性的影响进行了比较。两种药物均能完全抑制除瑞斯托霉素外所有受试激动剂引起的血小板聚集。此外，二者抑制人血小板与血管性血友病因子、纤维蛋白原、纤连蛋白和内皮下基质黏附的效力相似。两种药物均能剂量依赖性地抑制纤维蛋白原与洗涤后血小板的结合。在使用125I - YM337和125I - 阿昔单抗的结合试验中，富血小板血浆测定的YM337的解离常数（Kd）值为6.74±0.56 nM，阿昔单抗的Kd值为6.65±1.45 nM，YM337的结合位点数为42,700±3,000，阿昔单抗的结合位点数为76,000±5,400。两种药物均能从血小板的可溶部分沉淀出GPIIb/IIIa。相反，阿昔单抗能从人脐静脉内皮细胞的可溶部分沉淀出整合素αvβ3，而YM337则不能。两种药物均能剂量依赖性地抑制纤维蛋白原与纯化的GPIIb/IIIa的结合。相反，阿昔单抗能剂量依赖性地抑制玻连蛋白与纯化的整合素αvβ3的结合，而YM337则不能，这支持了阿昔单抗与整合素αvβ3发生反应的观点。因此，提示YM337与阿昔单抗结合GPIIb/IIIa的不同表位。这些结果表明，YM337特异性作用于血小板GPIIb/IIIa受体，对血小板聚集和血小板黏附具有与阿昔单抗相似的抑制特性。
