Hu Biao, Liu Tianyu, Li Liqiang, Shi Linqing, Yao Meinan, Li Chenzhen, Ma Xiaopan, Zhu Hua, Jia Bing, Wang Fan
Medical Isotopes Research Center and Department of Radiation Medicine, School of Basic Medical Sciences, Peking University, Beijing 100191, China.
Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Nuclear Medicine, Peking University Cancer Hospital & Institute, Beijing 100142, China.
Bioconjug Chem. 2022 Jul 20;33(7):1328-1339. doi: 10.1021/acs.bioconjchem.2c00209. Epub 2022 Jun 10.
Nanobodies have been developed rapidly as targeted probes for molecular imaging owing to their high affinity, outstanding tissue penetration, and rapid blood clearance. However, the short retention time at the tumor site limits their application in targeted radionuclide therapy. In this study, we designed a dual-targeting nanobody referred to as MIRC213-709, which can specifically bind to the HER2 receptor in tumor cell lines with high affinity (by nanobody MIRC213) and endogenous IgG in plasma to prolong the half-life by the MIRC213 C-terminal fusion nanobody, MIRC709. The nanobodies were site-specifically radiolabeled with Tc and Lu, and radiochemical purity was >95% after purification. The long blood circulation time and tumor retention property of Tc/Lu-MIRC213-709 were confirmed by a blood clearance assay, single-photon emission computed tomography (SPECT), and a biodistribution study. The blood clearance assay showed that the distribution phase half-life () and elimination phase half-life () of Tc-MIRC213-709 were 6.74- and 19.04-fold longer than those of Tc-MIRC213, respectively. The SPECT/CT and biodistribution results showed that the highest uptake of Lu-MIRC213 in the NCI-N87 model was 5.24 ± 0.95% ID/g at 6 h p.i., while the highest uptake of Lu-MIRC213-709 in the NCI-N87 model was 30.82 ± 7.29% ID/g at 48 h p.i. Compared with Lu-MIRC213, Lu-MIRC213-709 had a 16.9-fold increased tumor cumulative uptake (2606 ± 195.1 vs 153.9 ± 22.37% ID/g·h). The targeted radionuclide therapy assay was performed in the NCI-N87 tumor model, and treatment monitoring ended on day 32. The post-treatment/pretreatment tumor volumes were 12.99 ± 1.66, 3.58 ± 0.96, 1.26 ± 0.17, and 1.54 ± 0.50 in the 0, 9, and 18 MBq single-dose groups and the two 9 MBq divided dose group (14 days apart), respectively. All treatment groups showed significant therapeutic effects ( < 0.0001). Thus, fusion with the IgG-binding nanobody MIRC709 provides MIRC213 derivatives with improved metabolic properties for targeted radionuclide therapy.
由于具有高亲和力、出色的组织穿透性和快速的血液清除率，纳米抗体作为分子成像的靶向探针得到了迅速发展。然而，在肿瘤部位的短保留时间限制了它们在靶向放射性核素治疗中的应用。在本研究中，我们设计了一种双靶向纳米抗体，称为MIRC213-709，它可以通过纳米抗体MIRC213与肿瘤细胞系中的HER2受体高亲和力特异性结合，并与血浆中的内源性IgG结合，通过MIRC213 C末端融合纳米抗体MIRC709延长半衰期。这些纳米抗体用锝和镥进行了位点特异性放射性标记，纯化后放射化学纯度>95%。通过血液清除试验、单光子发射计算机断层扫描（SPECT）和生物分布研究证实了锝/镥-MIRC213-709的长血液循环时间和肿瘤保留特性。血液清除试验表明，锝-MIRC213-709的分布相半衰期（）和消除相半衰期（）分别比锝-MIRC213长6.74倍和19.04倍。SPECT/CT和生物分布结果表明，在NCI-N87模型中，镥-MIRC213在注射后6小时的最高摄取量为5.24±0.95%ID/g，而镥-MIRC213-709在NCI-N87模型中在注射后48小时的最高摄取量为30.82±7.29%ID/g。与镥-MIRC213相比，镥-MIRC213-709的肿瘤累积摄取增加了16.9倍（2606±195.1对153.9±22.37%ID/g·h）。在NCI-N87肿瘤模型中进行了靶向放射性核素治疗试验，治疗监测在第32天结束。在0、9和18 MBq单剂量组以及两个9 MBq分剂量组（间隔14天）中，治疗后/治疗前的肿瘤体积分别为12.99±1.66、3.58±0.96、1.26±0.17和1.54±0.50。所有治疗组均显示出显著的治疗效果（<0.0001）。因此，与IgG结合纳米抗体MIRC709融合为MIRC213衍生物提供了改善的代谢特性，用于靶向放射性核素治疗。
