Bifunctional ligand development for targeted Positron Emission Tomography (PET) using Zirconium-89

摘要 抗体对其抗原具有极强的特异性和亲和力，因此，正电子 使用靶向抗体的发射断层扫描(PET)是一种前沿的分子成像技术 癌症诊疗管理。放射性核素 当与抗体配对时，PET成像具有优异的物理性能。89Zr的78.41小时半衰期是一个 与长循环免疫球蛋白抗体的定位时间接近完美匹配。人们对此越来越感兴趣 在过去的十年里，89Zr作为一种与抗体配对的PET放射金属的使用急剧增加。 这些正在进行的临床研究和所有临床前研究使用当前标准的双功能配体(也 称为双功能螯合剂)：去铁胺B(DFO)。尽管图像质量通常非常高 很好，DFO不是89Zr的最佳配体。这表现在一些微妙的骨骼和非靶向摄取 放射性同位素由DFO释放出的亲骨性89Zr引起。因此，有必要开发一种改进的 双官能团的~(89)Zr配体通过提供一种改进的 替代DFO，减少对健康组织的吸收剂量，因此更安全的PET成像和 增强的图像质量。这个R21项目的设计总目标是形成优越的双功能配体 用于与抗体的偶联和对89Zr的稳定螯合。这样的双功能配体将消除~(89)Zr的损失 从体内的螯合和在骨中的摄取和非靶向问题。从本质上讲，这种新的双功能配体将 使用89Zr标记抗体促进更安全和改进的PET成像。在R21的支持下，我们将 一系列具有不同连接基化学结构的双功能配体的合成与表征 89Zr和与抗体的偶联。这种综合努力将与电子密度泛函计算和 分子动力学模拟以确定配位环境、相对稳定性和信息 放射金属化的简便性。我们将评估合成的配体与曲妥珠单抗(作为一种 研究良好的模型系统)，并用~(89)Zr标记，以确定其药代动力学和稳定性。这个 将对89Zr-配体-曲妥珠单抗结构进行评估，以确定其稳定性、生物分布和总体 与89Zr-DFO-曲妥珠单抗作为PET显像剂的比较

ABSTRACT Antibodies possess exquisite specificity and affinity for their antigens and as a consequence, Positron Emission Tomography (PET) using targeted antibodies is a molecular imaging technique at the forefront of cancer diagnosis and treatment management. Zirconium-89 (89Zr), a positron-emitting radionuclide, possesses excellent physical properties for PET imaging when paired with antibodies. The 78.41 hr half-life of 89Zr is a near perfect match to the localization time of long circulating IgG antibodies. There has been increased interest and a dramatic rise in the use of 89Zr as a PET radiometal paired with antibodies over the past ten years. These ongoing clinical studies and all pre-clinical studies use the current standard bifunctional ligand (also called a bifunctional chelator) for 89Zr: Desferrioxamine B (DFO). Although image quality is generally very good, DFO is not the optimal ligand for 89Zr. This is revealed by some subtle bone and non-target uptake of the radioisotope due to release of osteophilic 89Zr from DFO. There is therefore a need to develop an improved bifunctional ligand for 89Zr that will significantly improve 89Zr-antibody PET imaging by providing an improved alternative to DFO, reducing absorbed doses to healthy tissues and therefore safer PET imaging and enhanced image quality. This R21 project is designed with the overall goal to form superior bifunctional ligands for conjugation to antibodies and for stable chelation of 89Zr. Such a bifunctional ligand will eliminate 89Zr loss from the chelate in vivo and uptake in bone and non-target issue. In essence, this new bifunctional ligand will facilitate safer and improved PET imaging with 89Zr-labeled antibodies. Under the auspices of this R21, we will synthesize and characterize a series of bifunctional ligands with varying linker chemistries for the chelation of 89Zr and conjugation to antibodies. The synthetic effort will be paired with in silico DFT calculations and molecular dynamics simulations to identify the coordination environment, comparative stabilities and inform on the ease of radiometallation. We will evaluate the ligands synthesized when conjugated to trastuzumab (as a well-studied model system) and radiolabeled with 89Zr to determine their pharmacokinetics and stabilities. The 89Zr-ligand-trastuzumab constructs will be evaluated to determine their stability, biodistribution, and overall utility as PET imaging agents compared to 89Zr-DFO-trastuzumab