新型特异性凝血因子Ⅺa抑制剂的设计、合成及抗血栓活性研究

Anticoagulant drugs display a key role in the treatment of thrombotic disorders. However, the increasing risk of bleeding limits widely use of the approved anticoagulants, leading to narrow indications. Recent studies have shown that targeted factor Ⅺa (FⅪa) effectively inhibits thrombosis with minimal bleeding, which is considered as a potential safe and effective new anticoagulant strategy. Due to low selectivity and poor oral administration, few FⅪa inhibitors are entered into clinical trials. This project selects previously obtained compounds as lead compounds, focuses on specific amino acid Tyr58B at the trypsin-like active site of FⅪa and constructs a novel advantages scaffold based on the structure-based drug design methods including scaffold hopping and virtual screening. In addition, we optimize the substituents of molecular structure by fragment-based strategy and summarize the structure activity relationship, ultimately obtaining candidate molecule with target affinity, specificity, drug-likeness. Furthermore, the animal models are used to evaluated for antithrombotic activity and bleeding risk by specifically inhibiting FⅪa, preliminary confirming the effectiveness and safety of that specific FⅪa small molecule inhibitors in the treatment of thrombotic disorders. All efforts will provide useful clues and theoretical basis for the research of anticoagulant drugs.

抗凝血药物是治疗血栓性疾病的重要药物之一，但明显的出血风险限制了已上市抗凝血药的广泛应用，导致适应症狭窄。近来研究表明，靶向凝血因子Ⅺa（FⅪa）可有效抑制血栓形成并伴随较低出血倾向，被认为是潜在的安全有效的抗凝血新策略。由于选择性和口服成药性不佳，目前鲜有FⅪa小分子抑制剂进入临床研究。本项目以课题组前期获取的选择性FⅪa抑制剂为先导化合物，针对FⅪa类胰蛋白酶活性位点，聚焦Tyr58B等特异性氨基酸，综合运用骨架重构、虚拟筛选等基于结构的药物设计方法，构建新型的优势骨架结构，并采用基于片段的策略对分子骨架进行取代基优化，总结构效与构质关系，最终获得抑制活性、特异性、成药性方面性质均衡的候选分子。进一步利用动物模型研究特异性抑制FⅪa的抗血栓活性和出血风险，初步确证特异性FⅪa小分子抑制剂治疗血栓性疾病的有效性和安全性，为抗凝血药物的研究提供有益线索和理论依据。

本项目基于FXIa的活性位点，聚焦关键氨基酸残基Tyr58B，以已报道或虚拟筛选得到的活性小分子为先导化合物，采用基于结构的药物设计方法，合成了天冬氨酸、谷氨酸、甘氨酸骨架三大系列结构全新的FXIa抑制剂，共91个化合物。其中，部分化合物具有良好的FXIa抑制活性和酶选择性，特别是LF22和LF31。LF31对高度同源的PKal选择性在1000倍以上，是目前报导的选择性最好的小分子FXIa抑制剂。凝血时间测试显示LF31对内源性凝血通路具有明显抑制活性，而对外源性凝血通路无影响，进一步说明了其选择性。另外，LF31在体内表现出良好的抗血栓活性，同时，只显示低毒性和低出血风险，有作为候选化合物的潜质。生物学研究进一步表明，在高剂量给药情况下，选择性FXIa抑制比FXIa/PKal双抑制的出血风险低，从生物学层面证实了选择性FXIa抑制是出血风险的关键保障之一。