Purpose

Prostate cancer (PCa), characterized by tumor heterogeneity, may exhibit low or absent prostate-specific membrane antigen (PSMA) expression in cancerous lesions, limiting the detection sensitivity of monospecific probes. Given that fibroblast activation protein (FAP) is frequently overexpressed in the tumor microenvironment (TME), we developed a PSMA/FAP dual-targeting tracer to address this limitation.

Methods

The precursor (PSFA-01) was synthesized by coupling a quinolone-based FAP-targeting scaffold and EuK with HBED-CC via amide bonds. The dual-receptor-binding affinity and cell uptake of PSFA-01 and [^natGa]Ga-PSFA-01 was evaluated in vitro. Micro-PET/CT imaging was performed on 22Rv1 and U87MG tumor-bearing mice. The feasibility of [⁶⁸Ga]Ga-PSFA-01 PET/CT in a clinical setting was evaluated in a metastatic prostate cancer patient, and the results were compared with those of [⁶⁸Ga]Ga-FAPI-04 and [⁶⁸Ga]Ga-PSMA-11 PET/CT.

Results

PSFA-01 and [^natGa]Ga-PSFA-01 showed high affinity for both FAP and PSMA proteins (K_i = 0.14–1.02 nM). On micro-PET/CT imaging, the 22Rv1 tumor uptake of [⁶⁸Ga]Ga-PSFA-01 (SUV_max = 3.89 ± 0.47) was higher than that of [⁶⁸Ga]Ga-PSMA-11 (SUV_max = 2.96 ± 0.48). The U87MG tumor uptake of [⁶⁸Ga]Ga-PSFA-01 was significantly higher (SUV_max = 7.29 ± 1.13) than [⁶⁸Ga]Ga-FAPI-04 (SUV_max = 0.28 ± 0.12), showing tumor to muscle ratio as 12.68 ± 1.93 at 1 h p.i. On clinical trial, the primary tumor and metastatic lesions were distinctly identified by [⁶⁸Ga]Ga-PSFA-01 (21 lesions), demonstrating superior performance compared to [⁶⁸Ga]Ga-FAPI-04 (3 lesions) and [⁶⁸Ga]Ga-PSMA-11 (13 lesions) in terms of lesion count and specificity.

Conclusions

[⁶⁸Ga]Ga-PSFA-01 exhibited satisfactory PSMA and FAP dual-receptor-targeting properties both in vitro and in vivo. This study highlights the clinical feasibility of [⁶⁸Ga]Ga-PSFA-01 PET/CT for detecting metastatic tumors of prostate cancer more sensitively compared to monomeric [⁶⁸Ga]Ga-PSMA-11 and [⁶⁸Ga]Ga-FAPI-04, which also suggests that a PSMA/FAP dual-targeted radionuclide therapy could potentially overcome challenges related to tumor heterogeneity and insufficient PSMA expression in PCa.

Trial registration

Clinical trial registry NCT06387381, Registered 1 May 2024.

中文翻译：

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[68Ga]Ga-PSFA-01：PSMA/FAP 异二价示踪剂的设计、临床前评估和首次人体 PET 研究

 目的

前列腺癌 （PCa） 以肿瘤异质性为特征，在癌性病变中可能表现出低或不存在前列腺特异性膜抗原 （PSMA） 表达，从而限制了单特异性探针的检测灵敏度。鉴于成纤维细胞活化蛋白 （FAP） 在肿瘤微环境 （TME） 中经常过表达，我们开发了一种 PSMA/FAP 双靶向示踪剂来解决这一限制。

 方法

前体 （PSFA-01） 是通过酰胺键将基于喹诺酮类的 FAP 靶向支架和 EuK 与 HBED-CC 偶联而合成的。在体外评价 PSFA-01 和 [^natGa]Ga-PSFA-01 的双受体结合亲和力和细胞摄取。对 22Rv1 和 U87MG 荷瘤小鼠进行 Micro-PET/CT 成像。在转移性前列腺癌患者中评估 [⁶⁸Ga]Ga-PSFA-01 PET/CT 在临床环境中的可行性，并将结果与 [⁶⁸Ga]Ga-FAPI-04 和 [⁶⁸Ga]Ga-PSMA-11 PET/CT 的结果进行比较。

 结果

PSFA-01 和 [^natGa]Ga-PSFA-01 对 FAP 和 PSMA 蛋白均显示出高亲和力 （K = 0.14–1.02 nM）。在显微 PET/CT 成像上，[⁶⁸Ga]Ga-PSFA-01 的 22Rv1 肿瘤摄取 （SUV_max = 3.89 ± 0.47） 高于 [⁶⁸Ga]Ga-PSMA-11 （SUV_max = 2.96 ± 0.48）。[⁶⁸Ga]Ga-PSFA-01 的 U87MG 肿瘤摄取 （SUV_max = 7.29 ± 1.13） 显著高于 [⁶⁸Ga]Ga-FAPI-04 （SUV_max = 0.28 ± 0.12），显示肿瘤与肌肉的比值为 12.68 ± 1.93 在 1 小时 p.i。在临床试验中，[⁶⁸Ga]Ga-PSFA-01 （21 个病灶） 明确鉴定了原发肿瘤和转移病灶，与 [⁶⁸Ga]Ga-FAPI-04 （3 个病灶） 和 [⁶⁸Ga]Ga-PSMA-11 （13 个病灶） 相比，在病灶数量和特异性方面表现出优异的性能。

 结论

[⁶⁸加]Ga-PSFA-01 在体外和体内均表现出令人满意的 PSMA 和 FAP 双受体靶向特性。与单体 [⁶⁸Ga]Ga-PSMA-11 和 [⁶⁸Ga]Ga-FAPI-04 相比，本研究强调了 [⁶⁸Ga]Ga-PSFA-01 PET/CT 更灵敏地检测前列腺癌转移性肿瘤的临床可行性，这也表明 PSMA/FAP 双靶向放射性核素治疗有可能克服与肿瘤异质性和 PCa 中 PSMA 表达不足相关的挑战。

 试用注册

临床试验注册NCT06387381,2024 年 5 月 1 日注册。