Novel antithrombotic agents to prevent hemodialysis vascular access failure

目前，超过60%需要慢性血液透析的终末期肾病患者通过原生动静脉瘘（AVF）或合成移植物（AVG）进行透析。不幸的是，在AVG创建后6个月，初次失败率高达60%，在AVG构建后1年，失败率高达77%。手术创伤、反复穿刺、机械剪切应力、外来移植物材料和尿毒症可引起强烈的血栓形成反应，从而形成壁壁纤维蛋白和血小板丰富的底物，在其上发生过度的细胞迁移、增殖和基质沉积，导致avf和avg吻合周围区域的内膜增生（NH）。因此，限制壁血栓形成的早期事件可以有效地减少NH，这是狭窄和随后透析通路失败的主要原因。然而，目前可用的抗血小板和抗凝药物在临床安全剂量下预防NH的效果不足。EVAS Therapeutics公司开发了两种血栓形成位点靶向融合蛋白（ANV-6L15和TAP-ANV），它们可以特异性地停靠在血栓形成细胞的膜表面，并钝化启动和传播凝血级联反应的膜相关酶/辅因子复合物。由于其高亲和力的血栓形成位点靶向特性和相对较短的循环半衰期，融合蛋白可以发挥持久的抗血栓作用，而无需全身抗凝。这可能消除长期抗血栓治疗的需要，更有效地抑制壁血栓形成，降低出血风险。本课题的主要目标是开发这些有希望的候选药物，以预防NH，改善AVGs的功能和生存。如果成功，该策略可以应用于avf。第二阶段提案的具体目标是：具体目标1：建立生产ANV-6L15和TAP-ANV的中试规模工艺。在第一阶段开发的实验工艺将适用于重组蛋白的中试规模生产。具体目的2：研究TAP-ANV和ANV-6L15在猪血液透析血管通路模型中的治疗效果。将使用猪动静脉聚四氟乙烯（PTFE）移植物（AVG）模型检查NH形成和管腔通畅。目前还没有有效的治疗方法来提高血液透析动静脉通路的寿命。通过本研究，我们可能提供一种新颖而简单的治疗干预措施来提高血液透析AVGs和AVFs的寿命。这项研究的结果也将为IND申请和进一步的临床开发提供关键数据。

DESCRIPTION (provided by applicant): Currently, more than 60 % of end-stage renal diseases patients who require chronic hemodialysis are accessed through a native arteriovenous fistula (AVF) or synthetic graft (AVG). Unfortunately, primary failure rates were as high as 60 % at 6 months after AVF creation and 77% at 1 year after AVG construction. Surgical trauma, repeated needle punctures, mechanical shear stress, the foreign graft material and uremia can elicit a strong thrombotic response that lays down a mural fibrin- and platelet-rich substrate on which excessive cell migration, proliferation and matrix deposition occur, leading to neointimal hyperplasia (NH) in the peri-anastomotic regions of AVFs and AVGs. Limiting the early event of mural thrombosis may thus effectively reduce NH, which is the primary cause of stenosis and subsequent dialysis access failure. Currently available antiplatelet and anticoagulant drugs, however, have inadequate efficacies in preventing NH at clinically safe doses. EVAS Therapeutics has developed two thrombogenic site-targeted fusion Proteins (ANV-6L15 and TAP-ANV), which can specifically dock onto the membrane surfaces of thrombogenic cells and passivate the membrane-associated enzyme/cofactor complexes that initiate and propagate the clotting cascade. Due to their high-affinity thrombogenic site-targeting properties and relatively short circulating half-lives, the fusion proteins can exert long-lasting antithrombotic effect without systemic anticoagulation. This may eliminate the need for long-term antithrombotic therapy and inhibit mural thrombosis more effectively with reduced risks of bleeding. The main objective of this proposal is to develop these promising drug candidates for prevention of NH and improving the function and survival of AVGs. If successful, this strategy can be applied to AVFs. The specific aims of the phase II proposal are: Specific aim 1: Establish pilot-scale processes for production of ANV-6L15 and TAP-ANV. A bench process developed in phase I will be adapted for pilot-scale production of the recombinant proteins. Specific aim 2: Examine therapeutic efficacies of TAP-ANV and ANV-6L15 in porcine hemodialysis vascular access models. Both NH formation and lumen patency will be examined using a porcine arteriovenous polytetrafluoroethylene (PTFE) graft (AVG) model. Currently there are no effective therapies to improve hemodialysis arteriovenous access longevity. Through this study we may provide a novel and simple therapeutic intervention to improve longevity of hemodialysis PTFE AVGs and AVFs. Results from this study will also provide critical data for IND filing and further clinical development.