Zhang Mingru, Ye Jiajun, Xie Zhaojuan, Wang Yirong, Ma Wenhui, Kang Fei, Yang Weidong, Wang Jing, Chen Xiaoyuan
Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, China.
Departments of Diagnostic Radiology, Surgery, Chemical and Biomolecular Engineering, and Biomedical Engineering, Yong Loo Lin School of Medicine and Faculty of Engineering, National University of Singapore, Singapore 119074, Singapore.
Mol Pharm. 2022 May 2;19(5):1548-1556. doi: 10.1021/acs.molpharmaceut.2c00051. Epub 2022 Mar 31.
High and sustained renal radioactivity accumulation is a major challenge in peptide-based radionuclide imaging and therapy. However, neutral endopeptidase (NEP)-based enzymatic hydrolysis to release and excrete the radioactive fragments has been proven to be an effective and promising way to reduce renal accumulation. Despite the improvement, the effect is still far from being satisfactory. To further reduce kidney uptake, we studied the relationship between the enzymatic reaction rate and the substrate concentration and came up with a combined probe strategy. Model compounds Boc-MVK-Dde and Boc-MFK-Dde were used for an enzymatic digestion study. NOTA-Exendin 4 and NOTA-MVK-Exendin 4 were labeled with Cu for dose-dependent micro-positron emission tomography (PET) studies. Groups 1 and 2 were injected with 0.2 and 0.8 nmol of Cu-NOTA-Exendin 4, respectively. Groups 3-6 were injected with 0.2, 0.8, 1.0, and 1.4 nmol of Cu-NOTA-MVK-Exendin 4, respectively. Groups 7 and 8 were co-injected with 0.2 nmol of Cu-NOTA-MVK-Exendin 4 and NOTA-MVK-PEG5K (1.3 and 2.6 nmol). The radioactivity uptakes were determined and compared within and among the groups. The cleavage study for both Boc-MVK-Dde and Boc-MFK-Dde indicated that within a certain concentration range, the enzyme digestion rate increased with increasing substrate concentration. The microPET images showed that the renal clearance could be accelerated significantly by increasing the injection dose of Cu-NOTA-MVK-Exendin 4, with the kidney uptakes being 60.98, 43.01, and 16.10 % ID/g at 1 h for groups 3, 4 and 5, respectively. Unfortunately, the tumor uptakes were also significantly inhibited as the injected dose of the tracer increased. However, with the co-injection of NOTA-MVK-PEG5K, the renal accumulation was significantly decreased without hampering the tumor uptake. As a result, the tumor-to-kidney ratios were significantly improved, which were 1.93, 3.47, 1.74, and 3.38 times that of group 3 at 1, 4, 24, and 48 h, respectively. The enzymatic reaction rate of NEP is dependent on the concentration of the substrates both and . The combined probe strategy developed in this study can dramatically reduce the renal accumulation of a peptide radioligand without affecting the tumor uptake, which shows great potential in peptide-based radiotheranostics.
肾脏放射性的高度持续积累是基于肽的放射性核素成像和治疗中的一个重大挑战。然而，基于中性内肽酶（NEP）的酶促水解以释放和排泄放射性片段已被证明是减少肾脏积累的一种有效且有前景的方法。尽管有所改进，但效果仍远不尽人意。为了进一步降低肾脏摄取，我们研究了酶促反应速率与底物浓度之间的关系，并提出了一种联合探针策略。使用模型化合物Boc-MVK-Dde和Boc-MFK-Dde进行酶消化研究。用铜标记NOTA-Exendin 4和NOTA-MVK-Exendin 4进行剂量依赖性微正电子发射断层扫描（PET）研究。第1组和第2组分别注射0.2和0.8 nmol的Cu-NOTA-Exendin 4。第3 - 6组分别注射0.2、0.8、1.0和1.4 nmol的Cu-NOTA-MVK-Exendin 4。第7组和第8组共同注射0.2 nmol的Cu-NOTA-MVK-Exendin 4和NOTA-MVK-PEG5K（1.3和2.6 nmol）。测定并比较组内和组间的放射性摄取。对Boc-MVK-Dde和Boc-MFK-Dde的裂解研究表明，在一定浓度范围内，酶消化速率随底物浓度的增加而增加。微PET图像显示，通过增加Cu-NOTA-MVK-Exendin 4的注射剂量可显著加速肾脏清除，第3、4和5组在1小时时肾脏摄取分别为60.98、43.01和16.10% ID/g。不幸的是，随着示踪剂注射剂量的增加，肿瘤摄取也受到显著抑制。然而，通过共同注射NOTA-MVK-PEG5K，肾脏积累显著降低，而不影响肿瘤摄取。结果，肿瘤与肾脏的比值显著提高，在1、4、24和48小时时分别是第3组的1.93、3.47、1.74和3.38倍。NEP的酶促反应速率取决于底物的浓度。本研究中开发的联合探针策略可以显著降低肽放射性配体的肾脏积累，而不影响肿瘤摄取，这在基于肽的放射诊断治疗中显示出巨大潜力。
