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

摘要 抗体对它们的抗原具有精确的特异性和亲和力，因此， 使用靶向抗体的发射断层扫描（PET）是一种分子成像技术， 癌症诊断和治疗管理。锆-89（89 Zr）是一种发射正电子的放射性核素， 当与抗体配对时，PET成像具有优异的物理特性。89 Zr的半衰期为78.41小时， 与长循环IgG抗体的定位时间几乎完全匹配。越来越多的人 在过去的十年中，89 Zr作为PET放射性金属与抗体配对的使用急剧增加。 这些正在进行的临床研究和所有临床前研究使用目前的标准双功能配体（也称为双功能配体）。 称为双功能螯合剂）：去铁胺B（DFO）。虽然图像质量通常非常 好，DFO不是89 Zr的最佳配体。这是通过一些微妙的骨骼和非靶向摄取的 由于DFO释放的亲骨89 Zr导致放射性同位素。因此，需要开发一种改进的 89 Zr的双功能配体，其将通过提供改善的免疫原性而显著改善89 Zr-抗体PET成像。 替代DFO，减少健康组织的吸收剂量，因此更安全的PET成像， 增强的图像质量。该R21项目的总体目标是形成上级双功能配体 用于与抗体缀合和用于89 Zr的稳定螯合。这样的双官能配体将消除89 Zr损失 从体内螯合物和骨吸收和非靶组织。本质上，这种新的双功能配体将 使用89 Zr标记的抗体促进更安全和更好的PET成像。在R21的支持下，我们将 合成并表征一系列具有不同连接基化学的双官能配体，用于螯合 89 Zr和与抗体的缀合。合成工作将与计算机DFT计算配对， 分子动力学模拟，以确定协调环境，比较稳定性，并告知 辐射测量的简易性我们将评估当与曲妥珠单抗缀合时合成的配体（作为药物组合物）。 充分研究的模型系统）并用89 Zr放射性标记以测定它们的药代动力学和稳定性。的 将评价89 Zr-配体-曲妥珠单抗构建体以确定其稳定性、生物分布和总体生物学特性。 与89 Zr-DFO-曲妥珠单抗相比，作为PET显像剂的效用

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