Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599–7525, USA.
Thromb Res. 2011 Dec;128(6):570-6. doi: 10.1016/j.thromres.2011.04.009. Epub 2011 May 10.
The bypassing agent recombinant factor VIIa (rFVIIa) is efficacious in treating bleeding in hemophilia patients with inhibitors. Efforts have focused on the rational engineering of rFVIIa variants with increased hemostatic potential. One rFVIIa analog (V158D/E296V/M298Q-FVIIa, NN1731) improves thrombin generation and clotting in purified systems, whole blood from hemophilic patients and factor VIII-deficient mice.
We used calibrated automated thrombography and plasma clotting assays to compare effects of bypassing agents (rFVIIa, NN1731) on hemophilic clot formation, structure, and ability to resist fibrinolysis.
Both rFVIIa and NN1731 shortened the clotting onset and increased the maximum rate of fibrin formation and fibrin network density in hemophilic plasma clots. In the presence of tissue plasminogen activator, both rFVIIa and NN1731 shortened the time to peak turbidity (TTPeak(tPA)) and increased the area under the clot formation curve (AUC(tPA)). Phospholipids increased both rFVIIa and NN1731 activity in a lipid concentration-dependent manner. Estimated geometric mean concentrations of rFVIIa and NN1731 producing similar onset, rate, TTPeak(tPA), and AUC(tPA) as seen with 100% factors VIII and IX were: 24.5, 74.3, 29.7, and 37.1 nM rFVIIa, and 8.6, 31.2, 9.0, and 11.3 nM NN1731, respectively. In each case, the NN1731 concentration was significantly lower than rFVIIa.
These findings suggest that like rFVIIa, NN1731 improves the formation, structure, and stability of hemophilic clots. Higher lipid concentrations may facilitate assessment of both rFVIIa and NN1731 activity. NN1731 appears likely to support rapid clot formation in tissues with high endogenous fibrinolytic activity.
旁路制剂重组因子 VIIa（rFVIIa）在治疗有抑制剂的血友病患者出血方面具有疗效。人们一直致力于对具有更高止血潜能的 rFVIIa 变体进行合理的工程改造。一种 rFVIIa 类似物（V158D/E296V/M298Q-FVIIa，NN1731）可改善在纯化体系、血友病患者的全血和 VIII 因子缺乏的小鼠中的凝血酶生成和凝血。
我们使用校准的自动化血栓形成和血浆凝固测定法来比较旁路制剂（rFVIIa、NN1731）对血友病血栓形成、结构和抵抗纤维蛋白溶解的影响。
rFVIIa 和 NN1731 均缩短了血友病血浆凝块的凝血起始时间，并增加了纤维蛋白形成的最大速率和纤维蛋白网络密度。在组织型纤溶酶原激活物存在的情况下，rFVIIa 和 NN1731 均缩短了达最大浊度时间（TTPeak(tPA)），并增加了血栓形成曲线下面积（AUC(tPA)）。磷脂以脂质浓度依赖性的方式增加了 rFVIIa 和 NN1731 的活性。产生与 100%VIII 和 IX 因子相似的起始、速率、TTPeak(tPA)和 AUC(tPA)所需的 rFVIIa 和 NN1731 的估计几何平均浓度分别为：24.5、74.3、29.7 和 37.1 nM rFVIIa，和 8.6、31.2、9.0 和 11.3 nM NN1731。在每种情况下，NN1731 的浓度均显著低于 rFVIIa。
这些发现表明，与 rFVIIa 一样，NN1731 可改善血友病血栓的形成、结构和稳定性。更高的脂质浓度可能有助于评估 rFVIIa 和 NN1731 的活性。NN1731 似乎有可能支持在具有高内源性纤维蛋白溶解活性的组织中快速形成血栓。
