FAP-targeted radioligand therapy with 68Ga/177Lu-DOTA-2P(FAPI)2 enhance immunogenicity and synergize with PD-L1 inhibitors for improved antitumor efficacy

Dual-targeted alpha therapy mitigates prostate cancer and boosts immune checkpoint blockade therapy

Alpha radionuclide with a high emitting energy and short emitting range has emerged as a new tool for the treatment of advanced tumors; however, its clinical usage stringently depends on delivery vehicle. Here, we report on Sigma-1 receptor and PSMA dual-specific peptide with efficient 225‑actinium labeling (225Ac-S1R/PSMA-P) for targeted alpha therapy and alpha-immunotherapy of murine prostate tumor. 225Ac-S1R/PSMA-P with a high specific activity and radiostability exhibited upgraded cell binding and uptake while diminished efflux in RM1-PSMA+ cancer cells. Intriguingly, 225Ac-S1R/PSMA-P afforded a peak uptake of 34.7 ± 3.2 %ID/g and elevated the radioactivity in the tumor over 7 days, with a tumor/kidney ratio of 12.2 ± 1.2 and minimal deposition in blood and other normal tissues like liver and muscle. A single injection of 225Ac-S1R/PSMA-P effectively shrank large LNCaP-FGC tumors at 1.85 or 5.5 kBq, and completely eradicated highly malignant murine RM1-PSMA+/RM1 tumors at 33.3 kBq. We further showed that 225Ac-S1R/PSMA-P at a low dose of 3.7 kBq could boost immune checkpoint blockade therapy of murine RM1-PSMA+/RM1 tumor, leading to 5 out of 7 mice tumor-free that showed durable antitumor immune memory. 225Ac-S1R/PSMA-P with excellent targeting and immune activation ability has a great clinical potential for treating advanced prostate cancer patients.

Based on small molecules: development and application of fibroblast activation protein inhibitors radiopharmaceutical in tumor precision therapy

The discovery of biomarkers for malignant tumors is driving the development of new radiopharmaceuticals in nuclear medicine. The development and optimization of novel radiopharmaceuticals to occupy an increasingly important role in tumor diagnosis and treatment. In recent years, fibroblast activation protein (FAP) has gained attention as a promising tumor target due to its widespread expression across various tumors. FAP inhibitor (FAPI) radiopharmaceuticals are considered to be the most promising to be developed for targeting FAP due to their rapid and specific tumor targeting. This review briefly outlines the developmental history of FAP-targeted small-molecule enzyme activity inhibitors, highlighting the effective role of targeting molecules, linkers, and certain functional groups in the delivery of radioisotopes to cancerous tissues. These development strategies will serve as a reference for the further development and application of relevant radiopharmaceuticals. This review also delineates the progress on clinical FAPI as a radioisotope delivery vehicle for the targeted radioligand therapy of tumors and introduces the latest combination therapy involving FAPI radiopharmaceutical for tumor treatment. The findings provide novel therapeutic insights into the targeted radioligand therapy of tumors.

Comparison of PERCIST5, imPERCIST5, and PERCIMT Criteria for Early Assessment of Pembrolizumab Response with FDG-PET/CT in Metastatic Bladder Cancer Patients

Background/Objectives: Immunotherapy is an essential part of metastatic bladder cancer treatment. Our main objective was to study the prognostic value of FDG-PET/CT in early assessment of response to Pembrolizumab in metastatic bladder cancers using PERCIST5, imPERCIST5, and PERCIMT criteria. Methods: A total of 42 patients were evaluated with FDG-PET/CT at baseline and after 3-4 cycles of Pembrolizumab. Treatment response was blindly assessed with PERCIST5, imPERCIST5, and PERCIMT. Imaging and clinical data were collected. Progression was defined clinically using oncologist reports. Results: A total of 37 patients were evaluable with the PERCIST5 and imPERCIST5 criteria and included in the analysis. Median disease-specific progression-free survival (PFS) and overall survival (OS) were 152 and 363 days, respectively. All response criteria were significantly associated with PFS. When response was dichotomized in responders versus non-responders all scores were significantly associated with OS. When response was dichotomized in progressors versus non-progressors, only PERCIST5 (hazard ratio (HR) 2.2) and PERCIMT (HR 2.6) were significantly associated with OS, while imPERCIST was not (HR 1.6). Two patients had pseudoprogression (5%), both being adequately classified as non-progressors with PERCIMT criteria. Conclusions: Early response to immunotherapy as assessed with FDG-PET is a strong prognostic factor in bladder cancer patients, especially using the PERCIST5 or PERCIMT criteria. The latter seems clinically useful as it is simple to perform and its specific definition of metabolic progression correctly ruled-out patients with significant clinical benefit of Pembrolizumab in our study.

New Targets for Imaging in Nuclear Medicine

Nuclear medicine is rapidly evolving with new molecular imaging targets and advanced computational tools that promise to enhance diagnostic precision and personalized therapy. Recent years have seen a surge in novel PET and SPECT tracers, such as those targeting prostate-specific membrane antigen (PSMA) in prostate cancer, fibroblast activation protein (FAP) in tumor stroma, and tau protein in neurodegenerative disease. These tracers enable more specific visualization of disease processes compared to traditional agents, fitting into a broader shift toward precision imaging in oncology and neurology. In parallel, artificial intelligence (AI) and machine learning techniques are being integrated into tracer development and image analysis. AI-driven methods can accelerate radiopharmaceutical discovery, optimize pharmacokinetic properties, and assist in interpreting complex imaging datasets. This editorial provides an expanded overview of emerging imaging targets and techniques, including theranostic applications that pair diagnosis with radionuclide therapy, and examines how AI is augmenting nuclear medicine. We discuss the implications of these advancements within the field's historical trajectory and address the regulatory, manufacturing, and clinical challenges that must be navigated. Innovations in molecular targeting and AI are poised to transform nuclear medicine practice, enabling more personalized diagnostics and radiotheranostic strategies in the era of precision healthcare.

[18F]FAPI- 04 PET/CT for pathologic response assessment in pancreatic cancer patients with systemic treatment

PURPOSE

To study the association between [18F]FAPI- 04 uptake on positron emission tomography/computed tomography (PET/CT) and pathologic treatment response (PTR) in patients with pancreatic cancer (PC).

METHODS

We enrolled 59 patients from August 2021, of whom 28 underwent surgical treatment after systemic therapy. The patients were investigated for a correlation between baseline fibroblast activation protein inhibitor (FAPI) uptake and PTR using College of American Pathologists (CAP) scores. The FAPI PET variables include standardised uptake value (SUV)max, SUVmean, metabolic tumour volume (MTV), and total lesion FAP expression (TLF). A PET/CT scan obtained before surgery in 14 patients facilitated assessing changes in FAPI uptake through treatment, and their association with PTR. Multiplex immunohistochemistry (mIHC) analysis identified the FAPI biodistribution in the PC tumours.

RESULTS

The SUVmax correlated positively with FAP expression in PC tissues. However, there was no correlation between baseline variables and the CAP scores. Treatment resulted in remarkably reduced MTV and TLF in all patients. The baseline SUVmax and SUVmean of patients with a good PTR (CAP score ≤ 2) differed from those after treatment (p = 0.001). An FITC-FAPI probe intuitively showed that cancer-associated fibroblasts (CAFs) and tumour cells had a similar FITC-FAPI fluorescence intensity, indicating a negative association between tumour regression and [18F]FAPI- 04 uptake.

CONCLUSION

Greater changes in FAPI uptake through treatment were associated with a better PTR in patients with PC and might be valuable in predicting prolonged survival. These results are clinically meaningful when selecting candidates for conversion surgery during systemic treatment.