Dept. Pediatrics, Nara Medical University, Kashihara, Nara, Japan.
Chugai Pharmaceutical Co., Research Division, Gotemba, Shizuoka, Japan.
Thromb Res. 2021 Feb;198:7-16. doi: 10.1016/j.thromres.2020.11.026. Epub 2020 Nov 22.
Type 2N von Willebrand disease (2NVWD) is characterized by a mild to moderate reduction in plasma levels of factor (F)VIII associated with defective binding of von Willebrand factor (VWF) to FVIII and accelerated proteolysis and clearance of FVIII. The clinical phenotype in 2NVWD is often indistinguishable from mild/moderate hemophilia (H)A. Emicizumab is a bispecific antibody to FIX/FIXa and FX/FXa that mimics FVIIIa cofactor function, and emicizumab prophylaxis significantly reduces bleeding events in patients with severe HA.
We investigated the potential benefits of emicizumab in the hemostatic management of 2NVWD.
PATIENTS/METHODS: Perfusion chamber experiments were performed using whole blood from three 2NVWD patients with different clinical phenotypes (bleeding scores: 0, 6 and 20; mutations: p.R816W, p.R816W, and p.R365X/p.T791M, respectively). Furthermore, the impact of specific FVIII-VWF interactions on thrombus formation was investigated.
Defective thrombus formation that correlated with bleeding phenotype was evident in these 2NVWD patients. Emicizumab improved surface coverage and thrombus height in all cases. Multi-color immunostaining of thrombi further demonstrated that emicizumab enhanced thrombin generation and fibrin formation. The addition of FVIII alone to 2NVWD whole blood did not augment thrombus formation, while supplementation with FVIII/VWF complex enhanced platelet-fibrin interactions. Furthermore, an anti-FVIII monoclonal antibody known to interrupt the release of FVIIIa from VWF depressed these effects.
Emicizumab-induced enhancing effects of thrombus formation, independent on VWF, might be useful as an alternative therapy for 2NVWD patients. The extent of FVIII-VWF interaction should be optimal to deliver and release FVIII/FVIIIa on the activated platelet surface.
2N 型血管性血友病（2NVWD）的特征是血浆中因子（F）VIII 水平轻度至中度降低，同时伴有 von Willebrand 因子（VWF）与 FVIII 结合缺陷以及 FVIII 的快速蛋白水解和清除。2NVWD 的临床表型通常与轻度/中度血友病 A（HA）无法区分。依美珠单抗是一种针对 FIX/FIXa 和 FX/FXa 的双特异性抗体，可模拟 FVIIIa 辅因子功能，依美珠单抗预防治疗可显著减少重度 HA 患者的出血事件。
我们研究了依美珠单抗在 2NVWD 止血管理中的潜在益处。
患者/方法：使用来自三名具有不同临床表型的 2NVWD 患者的全血进行灌注室实验（出血评分：0、6 和 20；突变分别为：p.R816W、p.R816W 和 p.R365X/p.T791M）。此外，还研究了特定的 FVIII-VWF 相互作用对血栓形成的影响。
这些 2NVWD 患者的血栓形成缺陷与出血表型相关，这一点很明显。依美珠单抗改善了所有病例的表面覆盖率和血栓高度。血栓的多色免疫染色进一步表明，依美珠单抗增强了凝血酶生成和纤维蛋白形成。单独向 2NVWD 全血中添加 FVIII 并不能增强血栓形成，而添加 FVIII/VWF 复合物则增强了血小板-纤维蛋白相互作用。此外，一种已知可中断 FVIIIa 从 VWF 释放的抗 FVIII 单克隆抗体抑制了这些作用。
依美珠单抗诱导的血栓形成增强作用不依赖于 VWF，可能对 2NVWD 患者作为替代治疗方法有用。FVIII-VWF 相互作用的程度应最佳，以在激活的血小板表面上传递和释放 FVIII/FVIIIa。
