Development and application of new 18F-glycoconjugates for PET

正电子发射断层扫描（PET）在临床和实验分子成像中都有应用。然而，到目前为止，只有少数18f标记的肽放射性药物用于人体PET研究和临床试验。这主要是由于它们的放射性合成费时费力。在之前的资助期内，糖酰化前体已成功开发，适用于基于高效点击化学的同步18f标记和烷基化功能化肽的糖基化策略。利用该方法，制备了多种18F-糖基化生物分子（如avb3-仿射RGD肽、神经紧张素类肽、NPY衍生物以及神经紧张素受体和内皮素受体-a的非肽配体），并在体外和体内作为高仿射和选择性PET示踪剂进行了表征。我们可以证明糖基化本身和糖基残基中氟取代的位置在很大程度上决定了糖缀合物在体内的生物分布，正如一系列糖基化的RGD肽所证明的那样。此外，我们发现，与氟乙氧基类似物相比，糖基化对非肽内皮素受体配体的体内稳定性有积极的影响。该项目的进一步目标是：A)成功开发的18f糖缀合物用于血管生成的PET成像在动物模型（放射）治疗监测中的应用；B)开发神经紧张素受体-2的18f糖基化放射配体的亚型选择性。C)此外，已开发的18f -氟糖基化策略应适应细胞的放射性标记。本研究旨在利用PET成像分析癌症治疗的免疫学方法和快速细胞-细胞识别过程。为此，选择的[18F]氟脱氧葡萄糖酰叠氮化物用于细胞的点击化学标记，并使用合适的动物模型进行细胞运输实验，以确定细胞的生物动力学和PET成像数据的量化。该项目开发的18f -氟糖基化策略已被证明适用于示踪剂开发项目，如果成功适应PET的细胞运输研究，也将为临床前成像研究提供额外的潜力。

Positron emission tomography (PET) is established in clinical and experimental molecular imaging. However, so far there are only a few 18F-labeled peptide radiopharmaceuticals that are used in human PET studies and clinical trials. This is particularly ascribed to their time-consuming and demanding radiosyntheses. In the previous funding period glycosylazide precursors were successfully developed that are suitable for the efficient click chemistry-based strategy of concomitant 18F-labeling and glycosylation of alkynyl-functionalized peptides. Using this method, a variety of 18F- glycosylated biomolecules (e.g. avb3-affine RGD peptides, neurotensin peptoids, NPY derivatives, and also non-peptide ligands for the neurotensin receptor and the endothelin receptor-A) have been prepared and characterized in vitro and in vivo as highly affine and selective PET tracers. We could show that glycosylation itself and the position of the fluorine substitution in the glycosyl residues largely determined the biodistribution of glycoconjugates in vivo, as demonstrated on a series of glycosylated RGD peptides. Moreover, we showed that glycosylation has a positive influence on the in-vivo stability of a non-peptidic endothelin receptor ligand when compared to its fluoroethoxy analog. Further objectives of this project are: A) the application of successfully developed 18F-glycoconjugates for PET imaging of angiogenesis in the (radio)therapy monitoring in animal models, and B) the development of subtype-selective 18F-glycosylated radioligands for the neurotensin receptor-2. C) In addition, the developed 18F-fluoroglycosylation strategy should be adapted to the radiolabeling of cells. This aims to analyze immunological approaches to cancer therapy and rapid cell-cell recognition processes with PET imaging. For this purpose, selected [18F]fluorodeoxyglucosyl azide are used for click chemistry-based labeling of cells and subjected to cell-trafficking experiments using suitable animal models for the determination of the biokinetics of the cells and the quantification of PET imaging data. The 18F-fluoroglycosylation strategy developed in this project has already been proven suitable for tracer development projects and provides, in case of successful adaptation for cell trafficking studies with PET, also an additional potential for use in preclinical imaging studies.