FAP和αβ3双靶向分子标记物的结构优化及其在荷瘤鼠体内的生物分布研究

Structure Optimization and Their Biodistribution in Tumor-bearing Mice on FAP and αβ3 Dual Targeting Molecular Probes

  • 摘要: 为避免单靶标记物检测肿瘤时易出现误诊漏诊,本文设计并合成了能同时靶向FAP和αβ3受体的两种异源二聚体放射性显像剂68Ga-FAPI-RGD-01和68Ga-FAPI-RGD-02,并对其进行了microPET显像研究和初步U87MG荷瘤鼠生物分布研究。高效液相色谱分析结果表明,二者均具有良好的体外稳定性,无论是在生理盐水体系还是在胎牛血清体系中均可以维持大于95%的放化纯度。U87MG荷瘤鼠的microPET显像结果表明,相比于68Ga-FAPI-RGD-01,68Ga-FAPI-RGD-02具有更高的肿瘤摄取比,以及更低的心脏、肝脏、肾脏和肌肉组织摄取,表明其具有优异的药代动力学性能和肿瘤显像效果。以上结果表明,68Ga-FAPI-RGD-02具有临床疾病诊断的巨大潜力。

     

    Abstract: Fibroblast activation protein (FAP) is a crucial biomarker for the activation of tumor associated fibroblasts, served as an excellent target for both the diagnosis and treatment of cancer. In recent years, a variety of quinoline-based FAP inhibitors (FAPIs) have been developed, such as FAPI-02, FAPI-04 and FAPI-46, which were used to positron emission tomography (PET) imaging for clinical patients. However, high expression of FAP also occurs in chronic inflammation, fibrosis, arthritis, atherosclerotic plaques and cardiac fibrosis, which results in a compromised sensitivity/selectivity in distinguishing cancers from other FAP-positive diseases, such as chronic inflammation and fibrosis. Additionally, integrin receptor αβ3 highly expresses on the surface of various tumor cells and neovascular endothelial cells, including those in lung cancer, glioblastoma, breast cancer, and osteosarcoma, but absent in resting endothelial cells of normal tissues. Integrin receptor αβ3 plays an important role in regulating tumor growth, angiogenesis, local invasiveness, and metastatic potential. However, RGD-based radiotracers, including multimeric RGD peptides with enhanced integrin-targeting efficiency have only moderate tumor uptake. Based on this, in this paper two heterologous dimeric radiotracers, 68Ga-FAPI-RGD-01 and 68Ga-FAPI-RGD-02, were designed and synthesized, which are based on the quinoline-based FAPI-02 for targeting FAP, a cyclic RGD peptide for targeting αβ3, a 1,4,7-triazacyclononanetriacetic acid (NOTA) group for radionuclide labeling, and poly (ethylene glycol) linker. And then, the two radiotracers were used to study the microPET imaging and preliminary biodistribution in U87MG tumor-bearing mice. The excellent in vitro stability of both 68Ga-FAPI-RGD-01 and 68Ga-FAPI-RGD-02 was confirmed through high-performance liquid chromatography analysis, which could maintain radiochemical purity over 95% in PBS buffer solution or in serum medium for at least 4 h. The radiotracers also show favorable binding affinity and specificity through affinity assays of protein and receptor in vitro, and microPET imaging of U87MG tumor-bearing mice in vivo. Subsequently, the pharmacokinetics of the two radiotracers were assessed in healthy ICR mice, microPET imaging and biodistribution were performed in U87MG tumor-bearing mice, and comparing the performance of the 68Ga-FAPI-RGD-01 and 68Ga-FAPI-RGD-02 tracers. Compared to 68Ga-FAPI-RGD-01, 68Ga-FAPI-RGD-02 exhibits higher tumor uptake and lower uptake in the heart, liver, kidneys, and muscle tissues. In addition, compared to FAPI-02, RGD, and FAPI-02+RGD blocking groups, the tumor uptake and retention of 68Ga-FAPI-RGD-02 is very much higher than these blocking groups through microPET imaging studies. It is indicated that superior pharmacokinetic performance and tumor imaging effect for 68Ga-FAPI-RGD-02, demonstrating its enormous potential in clinical disease diagnosis.

     

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