Abstract：
Cathepsin B (CTSB) is a lysosomal protease that is overexpressed in tumor cells. Radioimmunoconjugates (RICs) composed of CTSB-recognizing chelating agents are expected to increase the molecular weights of their radiometabolites by forming conjugates with CTSB in cells, resulting in their improved retention in tumor cells. We designed a novel CTSB-recognizing trifunctional chelating agent, azide-[111In]In-DOTA-CTSB-substrate ([111In]In-ADCS), to synthesize a RIC, trastuzumab-[111In]In-ADCS ([111In]In-TADCS), and evaluated its utility to improve tumor retention of the RIC. [111In]In-ADCS and [111In]In-TADCS were synthesized with satisfactory yield and purity. [111In]In-ADCS was markedly stable in murine plasma until 96 h postincubation. [111In]In-ADCS showed binding to CTSB in vitro, and the conjugation was blocked by the addition of CTSB inhibitor. In the internalization assay, [111In]In-TADCS exhibited high-level retention in SK-OV-3 cells, indicating the in vitro utility of the CTSB-recognizing unit. In the biodistribution assay, [111In]In-TADCS showed high-level tumor accumulation, but the retention was hardly improved. In the first attempt to combine a CTSB-recognizing unit and RIC, these findings show the fundamental properties of the CTSB-recognizing trifunctional chelating agent to improve tumor retention of RICs.
摘要：
组织蛋白酶B(CTSB)是在肿瘤细胞中过表达的溶酶体蛋白酶。由CTSB识别螯合剂组成的放射免疫缀合物（RIC）有望通过与细胞中的CTSB形成缀合物来增加其放射性代谢物的分子量，导致它们在肿瘤细胞中的保留改善。我们设计了一种新型的CTSB识别三官能螯合剂，叠氮化物-[111In]In-DOTA-CTSB-底物([111In]In-ADCS)，合成RIC，trastuzumab-[111In]In-ADCS([111In]In-TADCS),并评估了其改善RIC肿瘤保留的效用。[111In]In-ADCS和[111In]In-TADCS以令人满意的产率和纯度合成。[111In]In-ADCS在小鼠血浆中明显稳定，直到孵育后96小时。[111In]In-ADCS在体外显示与CTSB结合，并且通过添加CTSB抑制剂来阻断缀合。在内化试验中，[111In]In-TADCS在SK-OV-3细胞中表现出高水平的保留，表明CTSB识别单元的体外效用。在生物分布分析中，[111In]In-TADCS显示出高水平的肿瘤积累，但保留率几乎没有改善。在结合CTSB识别单元和RIC的第一次尝试中，这些发现显示了CTSB识别三官能螯合剂改善RIC肿瘤保留的基本特性。
