基于结构生物学的Tubulysin衍生物的设计、合成及抗肿瘤活性研究

Antibody-drug conjugates (ADCs) is a novel targeted drug, which is obtained by chemical method coupling potent chemical compound with antibody. It combines the specificity of the antibody and high efficiency of chemical drug, which has been the latest development of tumor targeted drugs. Tubulysins are a family of tetrapeptides discovered from myxobacteria which can inhibit polymerization of microtubules, and exhibit extremely high antitumor activity (IC50 ﹤1nM), thereby can be modified as the new "warhead drugs". However, natural sources of Tubulysins are limited and they are difficult to be synthesized. In our previous work, we resolved the crystal structure of Tubulysin M-tubulin complex, and revealed its mechanism of molecular pharmacology，then summarized the key structure-activity relationship of Tubulysins. Based on the information of structural biology, following the requirements of "warhead drug", our final goal of this project is to design and synthesize a series of Tubulysin derivatives, and make a study of their anti-tumor effect to screen out novel Tubulysin derivatives which show high antimor activity and stability. Then making novel Tubulysin derivatives couple with anti-HER2 mutation antibody, and to study antimor activity of these ADCs. Finally we expect to get a series of novel "warhead drugs" which have independent intellectual property rights and lay a foundation for the development of ADC drugs.

抗体-药物偶联物（Antibody-drug conjugates, ADC）是将强效的化学药物（弹头）与抗体通过化学方法偶联得到的新一代靶向药物，充分发挥了抗体的靶向性与化学药物的高效性。Tubulysins是源于粘细菌中的一类非天然氨基酸组成的四肽化合物，可抑制微管聚合，抗肿瘤活性极强（IC50﹤1nM），有成为新型ADC “弹头”的潜力。然而，其面临天然来源少、合成难等问题。前期研究中，我们解析了Tubulysin M-微管蛋白的晶体结构，深入揭示了其分子药理学作用机制，总结了Tubulysins关键的构效关系。基于结构生物学的指导，本项目拟按照“弹头”的要求设计并合成一系列新的Tubulysin衍生物，筛选出活性高和稳定性好的新型Tubulysin衍生物，再与抗HER2突变抗体定向偶联后进行抗肿瘤药理学研究，最终获得具有自主知识产权的新型“弹头”，为ADC药物的研发奠定基础。

ADCs（Antibody Drug Conjugates）药物是将抗肿瘤抗体和强效的化疗药物（弹头药物）通过化学方法偶联，充分发挥了抗体的靶向性和化疗药物的高效性，是肿瘤靶向药物的热门发展方向。ADCs药物包括三个部分：针对肿瘤抗原的抗体、强效的化学药物和连接抗体与药物的连接子（Linker）。强效药物是ADCs中重要的组成部分，是ADCs高效杀伤效应的执行者。弹头药物的选择需根据ADCs所针对适应症和治疗靶点的特异程度而综合考虑。目前靶向抗体种类繁多，但是能够成为弹头药物的强活性分子却很少。因此，仍需不断探索和发现细胞毒性强，且有一定肿瘤选择性或不易耐药的新型弹头药物。Tubulysins是Höfle等人在2000年从粘细菌中发现的一类四肽化合物。Tubulysins能够抑制微管聚合，从而引发细胞凋亡，抗肿瘤活性极强。我们与南开大学的研究团队合作获得了活性和稳定性较好的衍生物14b，能否作为ADCs的弹头药物值得探索。为了初步了解抗Her2单抗偶联Tubulysin M和Tubulysin 14b对肿瘤治疗的效果，我们直接对Tubulysin M 和Tubulysin 14b末端羧基进行活化，然后偶联抗体而成ADCs。体内外药理学实验说明这两种ADCs具有较强的抗肿瘤效果，但也具有较大毒性，仍需要更进一步的研究。本项目研究结果将对以Tubulysin为弹头的ADCs药物的开发具有一定价值，并且奠定了基础。此外，基于同步辐射X-ray晶体学技术，我们与美国研究团队深入开展药物开发项目，阐明了一系列新颖骨架结构的微管抑制剂的分子作用机制，其中代号为VERU-111的小分子，目前已成为全球首款First-In-Class可口服微管蛋白抑制剂，并于2018年和2020年经美国FDA批准，在美国开展了针对晚期前列腺癌的II期临床试验(ClinicalTrials.gov Identifier: NCT03752099)和治疗新冠严重呼吸综合症的II期临床试验(ClinicalTrials.gov Identifier: NCT04388826)。本研究成果对新型微管抑制剂的作用靶点的明确，和以其为先导化合物的抗肿瘤和抗病毒药物的开发具有重要意义。