Purpose

Cadherin-17 (CDH17) is a calcium-dependent cell adhesion protein that is overexpressed in several adenocarcinomas, including gastric, colorectal, and pancreatic adenocarcinoma. High levels of CDH17 have been linked to metastatic disease and poor prognoses in patients with these malignancies, fueling interest in the protein as a target for diagnostics and therapeutics. Herein, we report the synthesis, in vitro validation, and in vivo evaluation of a CDH17-targeted ⁸⁹Zr-labeled immunoPET probe.

Methods

The CDH17-targeting mAb D2101 was modified with an isothiocyanate-bearing derivative of desferrioxamine (DFO) to produce a chelator-bearing immunoconjugate — DFO-D2101 — and flow cytometry and surface plasmon resonance (SPR) were used to interrogate its antigen-binding properties. The immunoconjugate was then radiolabeled with zirconium-89 (t_1/2 ~ 3.3 days), and the serum stability and immunoreactive fraction of [⁸⁹Zr]Zr-DFO-D2101 were determined. Finally, [⁸⁹Zr]Zr-DFO-D2101’s performance was evaluated in a trio of murine models of pancreatic ductal adenocarcinoma (PDAC): subcutaneous, orthotopic, and patient-derived xenografts (PDX). PET images were acquired over the course of 5 days, and terminal biodistribution data were collected after the final imaging time point.

Results

DFO-D2101 was produced with a degree of labeling of ~ 1.1 DFO/mAb. Flow cytometry with CDH17-expressing AsPC-1 cells demonstrated that the immunoconjugate binds to its target in a manner similar to its parent mAb, while SPR with recombinant CDH17 revealed that D2101 and DFO-D2101 exhibit nearly identical K_D values: 8.2 × 10⁻⁹ and 6.7 × 10⁻⁹ M, respectively. [⁸⁹Zr]Zr-DFO-D2101 was produced with a specific activity of 185 MBq/mg (5.0 mCi/mg), remained >80% stable in human serum over the course of 5 days, and boasted an immunoreactive fraction of >0.85. In all three murine models of PDAC, the radioimmunoconjugate yielded high contrast images, with high activity concentrations in tumor tissue and low uptake in non-target organs. Tumoral activity concentrations reached as high as >60 %ID/g in two of the cohorts bearing PDXs.

Conclusion

Taken together, these data underscore that [⁸⁹Zr]Zr-DFO-D2101 is a highly promising probe for the non-invasive visualization of CDH17 expression in PDAC. We contend that this radioimmunoconjugate could have a significant impact on the clinical management of patients with both PDAC and gastrointestinal adenocarcinoma, most likely as a theranostic imaging tool in support of CDH17-targeted therapies.

中文翻译：

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Cadherin-17 作为腺癌免疫 PET 的靶标

目的

Cadherin-17 (CDH17) 是一种钙依赖性细胞粘附蛋白，在多种腺癌中过度表达，包括胃癌、结直肠癌和胰腺癌。高水平的 CDH17 与这些恶性肿瘤患者的转移性疾病和不良预后有关，这激发了人们对该蛋白质作为诊断和治疗靶点的兴趣。在此，我们报告了CDH17 靶向⁸⁹ Zr 标记免疫 PET 探针的合成、体外验证和体内评估。

方法

靶向 CDH17 的 mAb D2101 用去铁敏 (DFO) 的异硫氰酸酯衍生物进行修饰，产生带有螯合剂的免疫缀合物 — DFO-D2101 — 并使用流式细胞术和表面等离子共振 (SPR) 来检测其抗原结合特性。然后用锆-89对免疫缀合物进行放射性标记（t _1/2 ~ 3.3天），并测定[ ⁸⁹ Zr]Zr-DFO-D2101的血清稳定性和免疫反应分数。最后，[ ⁸⁹ Zr]Zr-DFO-D2101 的性能在三种小鼠胰腺导管腺癌 (PDAC) 模型中进行了评估：皮下、原位和患者来源的异种移植物 (PDX)。 PET 图像在 5 天的时间内采集，并在最终成像时间点后收集最终生物分布数据。

结果

DFO-D2101 的标记程度约为 1.1 DFO/mAb。使用表达 CDH17 的 AsPC-1 细胞进行的流式细胞术表明，免疫缀合物以类似于其亲本 mAb 的方式与其靶标结合，而重组 CDH17 的 SPR 显示 D2101 和 DFO-D2101 表现出几乎相同的KD_值：8.2 × 10 ^{−分别为9}和6.7×10 ^-9 M。 [ ⁸⁹ Zr]Zr-DFO-D2101 的比活性为 185 MBq/mg (5.0 mCi/mg)，在 5 天的时间内在人血清中保持 >80% 的稳定性，并且免疫反应分数 >0.85 。在所有三种 PDAC 小鼠模型中，放射免疫缀合物均产生高对比度图像，肿瘤组织中活性浓度高，非靶器官吸收低。在两个携带 PDX 的队列中，肿瘤活性浓度高达 >60%ID/g。

结论

总而言之，这些数据强调，[ ⁸⁹ Zr]Zr-DFO-D2101 是一种非常有前途的探针，用于 PDAC 中 CDH17 表达的非侵入性可视化。我们认为，这种放射免疫结合物可能对 PDAC 和胃肠道腺癌患者的临床治疗产生重大影响，最有可能作为支持 CDH17 靶向治疗的治疗诊断成像工具。