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Updated: Aug 4, 2025
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Automated Preparation of [68Ga]Ga-3BP-3940 on a Synthesis Module for PET Imaging of the Tumor Microenvironment
Published on: April 25, 2025
Synthesis and Preclinical Evaluation of a Novel FAPI-04 Dimer for Cancer Theranostics
Xuan Zhong1,2, Jingru Guo3, Xiuping Han4
1Nanjing University of Chinese Medicine, Nanjing 210046, China.
Abstract:
Overexpression of fibroblast activation protein (FAP) in cancer-associated fibroblasts in a wide variety of tumors enables a highly selective targeting strategy using FAP inhibitors (FAPIs). Quinoline-based FAPIs labeled with radionuclides have been widely developed for tumor-targeted nuclear medicine imaging. However, the short retention time of FAPIs at the tumor site limits their application in radionuclide therapy. In this study, a novel FAPI-04 dimer was synthesized and labeled with radionuclides to prolong the retention time in tumors for imaging and therapy. To prepare the FAPI-04 dimer complex, DOTA-Suc-Lys-(FAPI-04)2, we used Fmoc-Lys(Boc)-OH as the linker to conjugate two FAPI-04 structures by an amide reaction. The resulting product was further modified by DOTA groups to allow for conjugation with radioactive metals. Both [68Ga]Ga-(FAPI-04)2 and [177Lu]Lu-(FAPI-04)2 showed a radiochemical purity of >99% and remained stable in vitro. In vivo, micro-PET images of SKOV3, A431, and H1299 xenografts revealed that the tumor uptake of [68Ga]Ga-(FAPI-04)2 was about twice that of [68Ga]Ga-FAPI-04 and that the accumulation of [68Ga]Ga-(FAPI-04)2 at the tumor site did not significantly decrease even 3h after injection. The tumor-abdomen ratio of [68Ga]Ga-(FAPI-04)2 images was significantly higher than that of [18F]F-FDG images. For radionuclide therapy, [177Lu]Lu-(FAPI-04)2 effectively retarded tumor growth and displayed good tolerance. In conclusion, the DOTA-Suc-Lys-(FAPI-04)2 design enhanced its uptake in FAP-expressing tumors, improved its retention time at the tumor site, and produced high-contrast imaging in xenografts after radionuclide labeling. Furthermore, it showed a noticeable antitumor effect. DOTA-Suc-Lys-(FAPI-04)2 provides a new approach for applying FAPI derivatives in tumor theranostics.
Insights
A novel dimeric fibroblast activation protein inhibitor (FAPI) derivative, DOTA-Suc-Lys-(FAPI-04)2, enhances tumor uptake and retention for improved nuclear imaging and radionuclide therapy. This FAPI dimer shows significant potential in cancer theranostics.
Area of Science:
- Nuclear Medicine
- Oncology
- Radiochemistry
Background:
- Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts across various tumors, making it a selective target.
- FAP inhibitors (FAPIs) labeled with radionuclides are used for tumor imaging, but their short retention limits therapeutic applications.
- Developing FAPIs with improved tumor retention is crucial for effective radionuclide therapy.
Purpose of the Study:
- To synthesize and evaluate a novel dimeric FAPI derivative (DOTA-Suc-Lys-(FAPI-04)2) for enhanced tumor targeting, imaging, and radionuclide therapy.
- To investigate the biodistribution, retention, and efficacy of radiolabeled FAPI dimer in preclinical cancer models.
- To assess the potential of the FAPI dimer for improved tumor theranostics.
Main Methods:
- Synthesis of the DOTA-Suc-Lys-(FAPI-04)2 complex using Fmoc-Lys(Boc)-OH as a linker.
- Radiolabeling of the dimer with Gallium-68 ([68Ga]) for imaging and Lutetium-177 ([177Lu]) for therapy.
- In vitro stability assessment and in vivo micro-PET imaging in SKOV3, A431, and H1299 xenografts.
- Evaluation of antitumor efficacy and tolerance of [177Lu]Lu-(FAPI-04)2 in tumor-bearing models.
Main Results:
- The radiolabeled FAPI dimer ([68Ga]Ga-(FAPI-04)2) demonstrated >99% radiochemical purity and in vitro stability.
- In vivo studies showed approximately twofold higher tumor uptake and prolonged retention of [68Ga]Ga-(FAPI-04)2 compared to the monomeric FAPI.
- The FAPI dimer achieved significantly higher tumor-to-background ratios than [18F]F-FDG.
- [177Lu]Lu-(FAPI-04)2 effectively inhibited tumor growth with good tolerance.
Conclusions:
- The DOTA-Suc-Lys-(FAPI-04)2 design significantly enhances FAP-targeting efficacy, improving tumor uptake and retention.
- Radiolabeled FAPI dimer enables high-contrast imaging and demonstrates a notable antitumor effect, supporting its theranostic potential.
- This novel dimeric FAPI derivative offers a promising strategy for advancing FAPI-based tumor theranostics.
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