DEVELOPING A TRANSLATABLE PLATFORM FOR REVERSIBLE PLATELET INHIBITION

理论基础和总体目标：我们的总体目标是开发一种快速可逆的抗血小板药物，在高度血栓形成的环境中抑制血栓形成，例如在冠状动脉血管重建术中遇到的情况。血小板在动脉粥样硬化斑块和其他血栓形成表面的无规律聚集是血栓形成的绝对先决条件，而血栓形成又代表近端血栓形成。 心肌梗死、设备故障、缺血性中风和心血管死亡的原因(1-3)。 抗血小板药物是从迅速扩大的基础血小板生物学知识库中直接发展而来的。现有的抗血小板疗法都不能阻止血栓形成的起始步骤--血小板粘连。因此，开发专门用于抑制作用于血小板黏附的生物相关靶点的新药，是朝着解决未得到满足的临床需求迈出的重要一步。糖蛋白(GP)Ib-IX-V是一种血小板黏附受体，属于 富含亮氨酸的重复蛋白家族。它的主要功能是在高切应力血流时启动血小板聚集，导致血栓形成(4)。当GP Ib-LX-V与血管性血友病因子(VWF)黏附后，血小板被激活，细胞骨架发生改变，并分泌血小板激动剂，使更多的血小板聚集到血栓形成中。与GP Ib/111a一样，GP Ib-IX-V是唯一的血小板受体 这在止血和血栓形成方面有非多余的作用，止血缺陷没有GP LLB/111a缺陷严重(4-7)。因此，GP Ib-IX-V-VWF相互作用的抑制剂有可能成为有效的抗血栓药物，具有比GP LLB/111 A更有利的安全性。 抗血栓治疗对于治疗血栓性疾病患者，特别是那些需要侵入性程序或手术的患者的整体有效性，在很大程度上受到这些治疗伴随的出血风险的限制。虽然责任机制定义不明确，但随之而来的是 止血功能受损和血管修复被认为是可能的因素。我们以前已经证明，蛋白质结合寡核苷酸(适配子)、抑制血小板的单链核酸、它们的功能配体和/或凝血蛋白具有高度特异性，可以很容易地被互补的寡核苷酸解毒剂逆转(8-10)。与这项建议特别相关的是，我们已经开发出针对VWF的适体，有可能抑制小鼠血栓形成，以及解毒寡核苷酸，可以迅速逆转适体的抗血小板活性(11)(Sullener实验室未发表的结果)。这种适配子-解毒剂策略 随着可主动控制的抗血栓药物的开发，具有潜在的广泛应用前景，当临床指征时，允许充分的药效作用，随后快速滴定或完全逆转。

Rationale and Overall Objective: Our overall goal is to develop a rapidly reversible antiplatelet agent that inhibits thrombus formation in highly prothrombotic settings such as those encountered during coronary revascularization procedures. Unregulated accumulation of platelets on atheromatous plaques and other thrombogenic surfaces is an absolute prerequisite for thrombus formation, which in turn represents a proximate cause of myocardial infarction, equipment malfunction, ischemic stroke and cardiovascular death(1-3). Antiplatelet drugs represent a direct outgrowth from a rapidly expanding knowledge base of fundamental platelet biology. None of the available antiplatelet therapies prevent the initiating step for thrombus formation- platelet adhesion. Accordingly, developing novel drugs that are engineered specifically to inhibit biologically relevant targets operative in platelet adhesion represents an important step toward addressing an unmet clinical need. Glycoprotein (GP) Ib-IX-V is a platelet adhesion receptor belonging to a leucine-rich repeat family of proteins. Its major function is to initiate platelet aggregation at high-shear stress blood flow, leading to thrombus formation(4). Following GP Ib-lX-V adhesion to von Willebrand Factor (VWF), platelets become activated, undergo cytoskeletal shape change and secrete platelet agonists that recruit additional platelets to the developing thrombus". Along with GP llb/llla, GP Ib-IX-V is the only platelet receptor that has a non-redundant role in hemostasis and thrombosis, with a hemostatic defect less serious than that of GP llb/llla deficiency(4-7). Thus, inhibitors of GP Ib-IX-V - VWF interaction may have the potential to become effective antithrombotic drugs with a more favorable safety proflle than GP llb/llla inhibitors. The overall effectiveness of antithrombotic therapy for managing patients with thrombotic disorders, particularly those requiring either invasive procedures or surgery has been limited in large part by the attendant bleeding risk which accompanies these therapies. While the responsible mechanisms are poorly defined, concomitant impairment of hemostasis and vascular repair have been proposed as likely contributors. We have previously shown that protein-binding oligonucleotides (aptamers), single-stranded nucleic acids that inhibit platelets, their functional ligands and/or coagulation proteins with high speciflcity can be readily reversed with complementary oligonucleotide antidotes(8-10). Of particular relevance to this proposal, we have developed aptamers against VWF that potentiy inhibit thrombosis in mice and antidote oligonucleotides that can rapidly reverse the antiplatelet activity of the aptamers(11) (Sullenger lab unpublished results). This aptamer-antidote strategy potentially offers broad applications, with the development of antithrombotic drugs which could be actively controlled, allowing full pharmacodynamic effects when clinically indicated, followed by rapid titration or complete reversal.