基于一步法的At-211标记新型小分子融合肽及其肿瘤靶向治疗的研究

As a cyclotron-produced nuclide and α-emitter, astatine-211 is particularly attractive for application to targeted radionuclide therapy (TRT) of cancer, especially for treatment of micrometastatic disease, cancer that is resistant to other forms of radiation, and cancer contained in compartmental spaces, due to the unique cytotoxic properties of the α-particles. Therefore, growing efforts have been devoted to the targeted radiotherapy experiments of At-211 labelled radiopharmaceuticals since 1970s, and great progress has been got more recently. However, there still exist some obstacles to further investigation of tumor targeted radiotherapy with At-211. Of which, the lack of more wonderful tumour-targeting carriers and more suitable labeling methods stills are the most important and key issues. The first goal of this proposal is to attempt a one-step procedure for At-211 labeling of proteins and peptides with high labeling yileds and low rdiolytic effects, especially for peptides with small molecular, by using N-succinimidyl 5-(tributylstannyl) -3-pyridinecarboxylate (SPC) or 2, 3, 5, 6-tetrafluorophenyl 3-(nido-carboranyl) propionate (TCP) as bi-functional linkers, and conjugating proteins or peptides with the linkers first, then labling with At-211. Aften then, a novel fusion peptide with high affinity to malignant lymphoma, which first synthesized in Sichuan University, is proposed to be labelled with At-211, and the At-211 labelled fusion peptide will be evaluated in vitro and vivo, included vitro and vivo stability, the biodistribution behavior and the targeted radiotherapy effects in animal model. By this project, a new method for At-211 labeling of proteins or peptides would be established and targeted radiotherapy of the At-211 labelled new fusion peptide for malignant lymphoma would be first investigated in animal model. All the result would be very useful to further study of tumor targeted radiotherapy with At-211 and other nuclides labelled compunds, especially with At-211 labelled small molecular peptides.

α核素At-211是最适宜于肿瘤靶向内放射治疗的理想核素之一。选择优良的载体和建立适宜的标记方法是At-211靶向药物研究的基础与关键。本课题拟以SPC或TCP为双功能偶联剂，通过先将其与蛋白质或多肽结合，再进行At-211标记的研究思路，以降低辐解效应，提高标记率，建立一条适合于At-211标记小分子多肽的一步间接方法。在此基础上，进行融合肽VHCDR1-VHFR2-VLCDR3的At-211标记及体内外动物实验研究，以期将我校近期自主合成并对恶性淋巴瘤具有良好亲和性的这种融合肽的靶向作用和At-211的极强细胞毒性相结合，实现At-211标记VHCDR1-VHFR2-VLCDR3用于恶性淋巴瘤的靶向治疗研究。研究结果不仅可为At-211标记蛋白质或多肽的方法提供一条新的思路，为At-211标记小分子肽类靶向治疗药物的深入研究奠定良好基础，而且对推动肿瘤的核素靶向治疗具有显著的现实意义。

α核素211At是最适宜于肿瘤靶向内放射治疗的理想核素之一。优良的靶向载体和适宜的标记方法是211At靶向药物研究的基础与关键。本基金以SPC等为双功能偶联剂，通过先将其与多肽或蛋白质结合，再进行211At标记的研究思路，以降低辐解效应，提高标记率，建立了一条适合于211A标记小分子多肽的一步间接方法。在此基础上，进行了多肽VP2等的At-211标记及体内外动物实验研究，顺利完成了预定的研究目标，取得了以下研究进展：.1）通过一步标记法，将211At标记到多肽VP2、小分子奥曲肽、单抗Rituximab（CD20）、特种蛋白pro-x、胶原-壳聚糖微球等多肽或蛋白质上，都得到了较高的标记率和较好的体外稳定性。211At标记VP2的标记率为25.5%，标记物211At-SPC-VP2即使在24h后其放化纯度仍可达97%；211At标记的壳聚糖-胶原微球的标记率达到92.2%，并具有较高的体外稳定性；.2）标记物与细胞结合实验表明，肝癌细胞HepG2与211At-SPC-VP2标记物的结合率在30-45%之间；肺癌细胞A549与211At-SPC-VP2标记物的结合率在10-15%之间；标记物211At-SPC-Pro-x与MDA-MB-231抗体可以特异性结合等；.3）标记物211At-SPC-VP2、211At-SPC-奥曲肽等在小鼠体内分布表明，这些标记物进入小鼠体内后代谢速度都较快，在甲状腺也都没有明显的摄取，说明这些标记药物在小鼠体内有良好的稳定性；.4）动物荷瘤实验表明，注射211At-SPC-VP2的荷瘤小鼠肿瘤生长明显减缓，同时通过计算得到抑瘤率达到56%，这说明211At-SPC-VP2具有一定靶向性且同时具有一定的肿瘤治疗效果。211At标记的壳聚糖-胶原微球具有较高的肿瘤-肌肉比，具有较好的靶向性。.这些研究结果不仅为211At标记小分子肽类靶向治疗药物的深入研究打下了良好基础，而且对促进和推动肿瘤的核素靶向治疗也具有显著的现实意义。同时，还为国内日渐萎缩的放射性药物与标记化合物领域培养了高层次专门人才。.到目前为止，基于本项目，已在国内外发表和交流论文23篇，其中已正式发表SCI收录论文7篇，国内核心期刊论文5篇；多人次参加全国学术交流会，并在国内学术会议上做邀请报告1次；先后有2名博士生、5名硕士生参与本课题的研究。