State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, 4221-116 Xiang'An South Rd, Xiamen 361102, China.
Institute of Clinical Pharmacy & Pharmacology, Jining First People's Hospital, Jining Medical University, Jining 272000, China.
Theranostics. 2022 Jan 1;12(1):422-433. doi: 10.7150/thno.68182. eCollection 2022.
Fibroblast activation protein (FAP) targeted molecular imaging radiotracers have shown promising preclinical and clinical results in tumor diagnosis. However, rapid clearance and inadequate tumor retention of these molecules have hindered them for further clinical translation in cancer therapy. In this study, we aimed to develop a series of albumin binder-truncated Evans blue (EB) modified FAP targeted radiotracers, and optimize the pharmacokinetic (PK) characteristics to overcome the existing limitations in order to apply in the radionuclide therapy of cancer. A series of compounds with the general structure of EB-FAPI-Bn were synthesized based on a FAP inhibitor (FAPI) variant (FAPI-02) and radiolabeled with LuCl. To verify the binding affinity and FAP targeting specificity of these tracers , U87MG cell uptake and competition assays were performed. Preclinical PK was evaluated in U87MG tumor-bearing mice using SPECT imaging and biodistribution studies. The lead compound EB-FAPI-B1 was selected and cancer therapeutic efficacy of Lu-EB-FAPI-B1 was assessed in U87MG tumor-bearing mice. Lu-EB-FAPI-B1, B2, B3, B4 were stable in PBS (pH 7.4) and saline for at least 24 h. EB-FAPI-B1 showed high binding affinity (IC = 16.5 nM) to FAP , which was comparable with that of FAPI-02 (IC = 10.9 nM). SPECT imaging and biodistribution studies of Lu-EB-FAPI-B1, B2, B3, B4 have proved their prominently improved tumor accumulation and retention at 96 h post-injection, especially for Lu-EB-FAPI-B1, high tumor uptake and low background signal make it the optimal compound. Compared to the saline group, noteworthy tumor growth inhibitions of Lu-EB-FAPI-B1 have been observed after administration of different dosages. In this study, several EB modified FAPI-02 related radiopharmaceuticals have been synthesized successfully and evaluated. High binding affinity and FAP targeting specificity were identified and . Remarkably enhanced tumor uptake and retention of EB-FAPI-B1 were found over the unmodified FAPI-02. Lu-EB-FAPI-B1 showed remarkable tumor growth suppression in U87MG tumor model with negligible side effects, indicating that Lu-EB-FAPI-B1 is promising for clinical application and transformation.
成纤维细胞激活蛋白（FAP）靶向分子成像放射性示踪剂在肿瘤诊断方面显示出有前途的临床前和临床结果。然而，这些分子的快速清除和不足的肿瘤保留阻碍了它们在癌症治疗中的进一步临床转化。在这项研究中，我们旨在开发一系列白蛋白结合物-截断 Evans 蓝（EB）修饰的 FAP 靶向放射性示踪剂，并优化药代动力学（PK）特征以克服现有局限性，以便应用于癌症的放射性核素治疗。 基于 FAP 抑制剂（FAPI）变体（FAPI-02），我们合成了一系列具有 EB-FAPI-Bn 一般结构的化合物，并使用 LuCl 进行放射性标记。为了验证这些示踪剂的结合亲和力和 FAP 靶向特异性，进行了 U87MG 细胞摄取和竞争测定。使用 SPECT 成像和生物分布研究在 U87MG 荷瘤小鼠中评估了初步的 PK。选择了先导化合物 EB-FAPI-B1，并在 U87MG 荷瘤小鼠中评估了 Lu-EB-FAPI-B1 的癌症治疗效果。在 PBS（pH 7.4）和盐水中，Lu-EB-FAPI-B1、B2、B3、B4 至少稳定 24 小时。EB-FAPI-B1 对 FAP 表现出高结合亲和力（IC = 16.5 nM），与 FAPI-02（IC = 10.9 nM）相当。Lu-EB-FAPI-B1、B2、B3、B4 的 SPECT 成像和生物分布研究证明，它们在注射后 96 小时的肿瘤积累和保留方面有了明显的改善，特别是 Lu-EB-FAPI-B1，高肿瘤摄取和低背景信号使其成为最佳化合物。与生理盐水组相比，在给予不同剂量后，观察到 Lu-EB-FAPI-B1 对肿瘤生长的显著抑制。 在这项研究中，成功合成并评估了几种 EB 修饰的 FAPI-02 相关放射性药物。鉴定了高结合亲和力和 FAP 靶向特异性。发现 EB-FAPI-B1 的肿瘤摄取和保留显著增强。Lu-EB-FAPI-B1 在 U87MG 肿瘤模型中表现出显著的肿瘤生长抑制作用，且副作用可忽略不计，表明 Lu-EB-FAPI-B1 具有临床应用和转化的潜力。
