The acyclic chelator HBED-CC has attained huge clinical significance owing to high thermodynamic and kinetic stability of 68 Ga-HBED-CC chelate. It provides an excellent platform for quick preparation of 68 Ga-based radiotracers in high yield. Thus the present study aimed at conjugation of gastrin releasing peptide receptor (GRPr) antagonist, RM26, with HBED-CC chelator for 68 Ga-labeling. In vitro and vivo behavior of the peptide tracer, 68 Ga-HBED-CC-PEG2 -RM26 was assessed and compared with 68 Ga-NODAGA-PEG2 -RM26. The peptide tracers, 68 Ga-HBED-CC-PEG2 -RM26 and 68 Ga-NODAGA-PEG2 -RM26 prepared either by wet chemistry or formulated using freeze-dried kits exhibited excellent radiochemical yield and in vitro stability. The two peptide tracers cleared rapidly from the blood. Biodistribution studies in normal mice demonstrated slightly higher or comparable uptake of 68 Ga-HBED-CC-PEG2 -RM26 in GRPr-expressing organs pancreas, stomach and intestine. The preliminary studies suggest high potential of 68 Ga-HBED-CC-PEG2 -RM26 for further investigation as a GRPr imaging agent and the wide scope of HBED-CC chelator in development of 68 Ga-based peptide tracers.

中文翻译：

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GRPr 拮抗剂 68 Ga-HBED-CC-RM26 的合成、放射性标记和评价

由于 68 Ga-HBED-CC 螯合物的高热力学和动力学稳定性，无环螯合剂 HBED-CC 已获得巨大的临床意义。它为以高产率快速制备 68 Ga 基放射性示踪剂提供了一个极好的平台。因此，本研究旨在将胃泌素释放肽受体 (GRPr) 拮抗剂 RM26 与用于 68 Ga 标记的 HBED-CC 螯合剂结合。评估肽示踪剂 68 Ga-HBED-CC-PEG2 -RM26 的体外和体内行为，并与 68 Ga-NODAGA-PEG2 -RM26 进行比较。通过湿化学制备或使用冻干试剂盒配制的肽示踪剂 68 Ga-HBED-CC-PEG2 -RM26 和 68 Ga-NODAGA-PEG2 -RM26 表现出优异的放射化学产率和体外稳定性。两种肽示踪剂从血液中迅速清除。正常小鼠的生物分布研究表明，在表达 GRPr 的器官胰腺、胃和肠中，68 Ga-HBED-CC-PEG2 -RM26 的吸收略高或相当。初步研究表明 68 Ga-HBED-CC-PEG2 -RM26 作为 GRPr 显像剂和 HBED-CC 螯合剂在开发 68 Ga 肽示踪剂方面具有广泛的潜力，可用于进一步研究。