Peng Tukang, Huang Gang, Zhao Haitao, Liu Jianjun
Department of Nuclear Medicine, Institute of Clinical Nuclear Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 210000, China.
Shanghai Key Laboratory of Molecular Imaging, Shanghai University of Medicine and Health Sciences, Shanghai 210000, China.
Bioconjug Chem. 2025 Jan 15;36(1):116-126. doi: 10.1021/acs.bioconjchem.4c00564. Epub 2025 Jan 2.
To enhance the affinity of peptide ligands for their targets, covalent warheads can be engineered to facilitate irreversible binding. This study aimed at exploring the potential of a Ga-labeled peptidomimetic radioligand, [Ga]Ga-DOTA-RQAR-kbt, for PET imaging through its irreversible binding to the suppression of tumorigenicity 14 (ST14). An Arg-Gln-Ala-Arg (RQAR) tetrapeptide was conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid for gallium-68 radiolabeling. The covalent warhead ketobenzothiazole was constructed as a serine trap for ST14 protease, resulting in the formation of DOTA-RQAR-kbt. We compared both the and properties of [Ga]Ga-DOTA-RQAR-kbt with those of its reversible-binding counterparts, [Ga]Ga-DOTA-RQAR-OH. DOTA-RQAR-kbt exhibits high affinity for ST14 and irreversibly binds to ST14, as evidenced by the lack of ST14 activity recovery following ultrafiltration. In contrast, DOTA-RQAR-OH shows reversible binding and has low affinity for ST14. PET/CT imaging confirmed the superior tumor targeting of [Ga]Ga-DOTA-RQAR-kbt compared to the [Ga]Ga-DOTA-RQAR-OH, with robust signals observed at 0.5, 1, and 2 h postinjection. Blocking studies underscored the probe's specificity, as they revealed a marked reduction in tumor uptake in the presence of excess RQAR-kbt. Biodistribution studies demonstrated significantly higher tumor uptake for [Ga]Ga-DOTA-RQAR-kbt, with 0.89 ± 0.03%ID/g at 1 h postinjection, which was reduced to 0.25 ± 0.03%ID/g ( < 0.01) in the presence of excess RQAR-kbt. In this proof-of-concept study, an irreversibly binding peptidomimetic radioligand targeting ST14 was evaluated, demonstrating improved tumor uptake compared with its reversibly binding counterparts. This approach holds promise for improving the potency of covalent radiotracers as PET agents.
为了增强肽配体与其靶标的亲和力，可以设计共价弹头以促进不可逆结合。本研究旨在探索一种镓标记的拟肽放射性配体[Ga]Ga-DOTA-RQAR-kbt通过与抑癌基因14（ST14）不可逆结合用于正电子发射断层扫描（PET）成像的潜力。将精氨酸-谷氨酰胺-丙氨酸-精氨酸（RQAR）四肽与1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸缀合用于镓-68放射性标记。构建共价弹头酮苯并噻唑作为ST14蛋白酶的丝氨酸陷阱，从而形成DOTA-RQAR-kbt。我们比较了[Ga]Ga-DOTA-RQAR-kbt与其可逆结合对应物[Ga]Ga-DOTA-RQAR-OH的体外和体内特性。DOTA-RQAR-kbt对ST14表现出高亲和力并与其不可逆结合，超滤后ST14活性未恢复证明了这一点。相比之下，DOTA-RQAR-OH显示出可逆结合且对ST14的亲和力较低。PET/CT成像证实，与[Ga]Ga-DOTA-RQAR-OH相比，[Ga]Ga-DOTA-RQAR-kbt具有更好的肿瘤靶向性，注射后0.5、1和2小时观察到强烈信号。阻断研究强调了该探针的特异性，因为在存在过量RQAR-kbt的情况下肿瘤摄取明显降低。生物分布研究表明，[Ga]Ga-DOTA-RQAR-kbt的肿瘤摄取显著更高，注射后1小时为0.89±0.03%ID/g，在存在过量RQAR-kbt的情况下降至0.25±0.03%ID/g（<0.01）。在这项概念验证研究中，评估了一种靶向ST14的不可逆结合拟肽放射性配体，与可逆结合对应物相比，其肿瘤摄取有所改善。这种方法有望提高共价放射性示踪剂作为PET试剂的效能。
