Trop2 immuno-PET/CT imaging of prostate cancer: a proof-of-concept translational study

Prostate cancer (PCa) is the second leading cause of death in men and is highly prone to metastasis. This study aims to develop the novel immuno-PET/CT tracer targeting trophoblast cell surface antigen 2 (Trop2), a transmembrane protein overexpressed in aggressive prostate malignancies, and to investigate its diagnostic value in preclinical studies as well as its potential utility in detecting metastases in PCa patients.

Integrated analysis of TCGA, GEO, and HPA datasets revealed Trop2 overexpression in prostate adenocarcinoma. By labeling two Trop2-targeted nanobodies (His-tagged T4 and His-tag-free RT4) with ⁶⁸Ga and ¹⁸F, we synthesized three radiotracers, [⁶⁸Ga]Ga-NOTA-T4, [¹⁸F]AlF-RESCA-T4, and [¹⁸F]AlF-RESCA-RT4. Preclinical validation included cellular assays and xenograft studies for ⁶⁸Ga/¹⁸F-T4 variants, followed by a first-in-human trial evaluating [¹⁸F]AlF-RESCA-RT4 in ten treatment-naïve PCa patients.

Bioinformatics analysis demonstrated Trop2 as a promising target for PCa diagnosis and treatment. In preclinical studies, both [⁶⁸Ga]Ga-NOTA-T4 and [¹⁸F]AlF-RESCA-T4 illustrated high affinity to Trop2, specific tumor uptake (4.33 ± 0.38 %ID/g and 5.50 ± 0.69 %ID/g at 60 min, respectively) in Trop2-positive xenograft mouse models with minimal background distribution. In the translational study, [¹⁸F]AlF-RESCA-RT4 outperformed standard [¹⁸F]-FDG imaging in metastatic prostate cancer patients, detecting 62.4% more lymph node metastases (SUVmax 21.58 ± 13.12 vs. 4.80 ± 1.77) and 69.4% more bone lesions (SUVmax 7.83 ± 4.32 vs. 4.72 ± 1.22). No adverse events were observed.

This work successfully establishes that Trop2 is a new biomarker for PCa, and Trop2 immuno-PET/CT imaging can detect PCa lymph node and osseous metastases. The superior tumor-to-background contrast and clinical safety of [¹⁸F]AlF-RESCA-RT4 support its translational potential to guide Trop2-targeted therapies and enhance personalized treatment strategies.

NCT06851663. Retrospectively registered 02/24/2025.