Copper-64-immunoPET imaging: bench to bedside

Nanobody-Based PET Imaging of CD47 Expression in Thyroid Carcinoma

Thyroid cancer is the most common malignant tumor in the endocrine system. A significant correlation has been established between elevated CD47 expression and the progression of thyroid carcinoma. This study aims to evaluate the diagnostic potential of immuno-positron emission tomography (immunoPET) utilizing CD47-targeting nanobodies in thyroid cancer tumor models. Immunohistochemistry (IHC) was employed to evaluate CD47 expression in patients with thyroid cancer, as well as in anaplastic thyroid carcinoma (ATC) xenograft tumor (OCUT-2C) and differentiated thyroid cancer (DTC) xenograft tumors (TPC-1 and BCPAP). Two nanobodies, C2 and its albumin-binding derivative (ABDC2), specifically targeting CD47 were labeled with 68Ga. The tracers were evaluated using immunoPET imaging in models of thyroid cancer. IHC revealed that CD47 was highly expressed in 34.69% of the tumor tissues from patients with thyroid cancer. Additionally, high levels of CD47 expression were observed in OCUT-2C, TPC-1, and BCPAP tumor tissues. Micro-PET imaging using [68Ga]Ga-NOTA-C2 and [68Ga]Ga-NOTA-ABDC2 demonstrated clear visualization of OCUT-2C tumors. Notably, the tumor uptake of [68Ga]Ga-NOTA-ABDC2 was significantly higher than that of [68Ga]Ga-NOTA-C2 at each imaging time point. Additionally, [68Ga]Ga-NOTA-ABDC2 exhibited specific uptake in the TPC-1 and BCPAP models. This study confirmed that [68Ga]Ga-NOTA-ABDC2 as a innovative PET imaging radiotracer targeting CD47 presented specific and higher tumor uptake to accurately identify CD47 expression and diagnose thyroid cancer. The clinical application of these imaging strategies may aid in selecting patients for CD47-targeted therapies and evaluating their subsequent responses.

ImmunoPET Imaging of Trop2 Expression in Bladder Cancer Using [64Cu]Cu-NOTA-Trodelvy

Trop2 exhibits significantly elevated expression in numerous solid malignancies, playing a crucial role in tumor advancement, whereas its presence in healthy tissues is minimal. In this study, we investigated Trop2 expression in bladder cancer models using [64Cu]Cu-NOTA-Trodelvy for immunoPET imaging. In HT-1376 models, [64Cu]Cu-NOTA-Trodelvy effectively visualized tumor as early as 12 h p.i. (10.30 ± 1.45% ID/g), with tumor uptake increasing and peaking at 48 h p.i. (13.73 ± 1.16% ID/g), highlighting its potential for tumor imaging. Control groups also demonstrated low tumor uptake (5.27 ± 1.14% ID/g at 48 h in the blocking group; 6.33 ± 0.74% ID/g at 48 h in UM-UC-3; 4.50 ± 0.30% ID/g at 48 h in the [64Cu]Cu-NOTA-IgG group). Long-term fluorescence imaging further confirmed the tumor uptake rate in the IRDye 800CW-Trodelvy group was significantly higher than in the IRDye 800CW-Trodelvy blockade group (P < 0.001). Our findings demonstrated that [64Cu]Cu-NOTA-Trodelvy enables specific and prolonged tumor accumulation in bladder cancer models, providing precise and noninvasive monitoring of Trop2 expression.

Preclinical evaluation of 64Cu/177Lu-labelled anti-CD30 monoclonal antibody for theranostics in CD30-positive lymphoma

PURPOSE

CD30 serves as an ideal therapeutic target for lymphoma, but its variable expression and high relapse rate pose challenges in targeted therapy. This study aims to label the anti-CD30 monoclonal antibody with 64Cu/177Lu for immuno-positron emission tomography (immuno-PET) and radioimmunotherapy (RIT).

METHODS

CD30 binding kinetics of anti-CD30-IgG (IMB16) were measured by Biolayer interferometry (BLI). Western blotting screened lymphoma cell lines for CD30 expression. Flow cytometry and immunofluorescence validated the specific binding of IMB16. IMB16 was conjugated to p-SCN-Bn-NOTA(NOTA) and p-SCN-Bn-DOTA(DOTA) for radiolabeling with 64Cu and 177Lu. [64Cu]Cu-NOTA-IMB16 and [177Lu]Lu-DOTA-IMB16 were used for immuno-PET and RIT in subcutaneous lymphoma NSG mouse models.

RESULTS

IMB16 had a strong binding affinity to CD30 according to the BLI. Western blotting revealed high CD30 expression in Karpas299 cells and negative expression in Raji cells. Flow cytometry and immunofluorescence confirmed specific binding of IMB16 to CD30 on cell surface. Radiochemical purity of [64Cu]Cu-NOTA-IMB16 and [177Lu]Lu-DOTA-IMB16 exceeded 95%. In Immuno-PET imaging, CD30-positive Karpas299 tumours had a mean uptake value of 19.2 ± 0.9%ID/g (n = 3) at 24 h post-injection, significantly higher than Karpas299-blocked and Raji-negative groups (P < 0.001). A high radiation dose (300µCi) of [177Lu]Lu-DOTA-IMB16 significantly inhibited tumour growth (80.2 ± 17.6% standardized tumour volume, n = 5) at 10 days post-injection, compared to controls. Ex vivo biodistribution and histological staining supported in vivo PET imaging and RIT results.

CONCLUSIONS

Labelling IMB16 with 64Cu enabled non-invasive assessment of CD30 expression, while 177Lu labelling effectively suppressed tumour growth in CD30-positive lymphoma. CD30-targeted theranostic show promise for patient stratification and treatment enhancement, warranting further clinical evaluation.

Navigating the landscape of PD-1/PD-L1 imaging tracers: from challenges to opportunities

Immunotherapy targeted to immune checkpoint inhibitors, such as the program cell death receptor (PD-1) and its ligand (PD-L1), has revolutionized cancer treatment. However, it is now well-known that PD-1/PD-L1 immunotherapy response is inconsistent among patients. The current challenge is to customize treatment regimens per patient, which could be possible if the PD-1/PD-L1 expression and dynamic landscape are known. With positron emission tomography (PET) imaging, it is possible to image these immune targets non-invasively and system-wide during therapy. A successful PET imaging tracer should meet specific criteria concerning target affinity, specificity, clearance rate and target-specific uptake, to name a few. The structural profile of such a tracer will define its properties and can be used to optimize tracers in development and design new ones. Currently, a range of PD-1/PD-L1-targeting PET tracers are available from different molecular categories that have shown impressive preclinical and clinical results, each with its own advantages and disadvantages. This review will provide an overview of current PET tracers targeting the PD-1/PD-L1 axis. Antibody, peptide, and antibody fragment tracers will be discussed with respect to their molecular characteristics and binding properties and ways to optimize them.

State of the Art in Radiolabeling of Antibodies with Common and Uncommon Radiometals for Preclinical and Clinical Immuno-PET

Inert and stable radiolabeling of monoclonal antibodies (mAb), antibody fragments, or antibody mimetics with radiometals is a prerequisite for immuno-PET. While radiolabeling is preferably fast, mild, efficient, and reproducible, especially when applied for human use in a current Good Manufacturing Practice compliant way, it is crucial that the obtained radioimmunoconjugate is stable and shows preserved immunoreactivity and in vivo behavior. Radiometals and chelators have extensively been evaluated to come to the most ideal radiometal–chelator pair for each type of antibody derivative. Although PET imaging of antibodies is a relatively recent tool, applications with ⁸⁹Zr, ⁶⁴Cu, and ⁶⁸Ga have greatly increased in recent years, especially in the clinical setting, while other less common radionuclides such as ⁵²Mn, ⁸⁶Y, ⁶⁶Ga, and ⁴⁴Sc, but also ¹⁸F as in [¹⁸F]AlF are emerging promising candidates for the radiolabeling of antibodies. This review presents a state of the art overview of the practical aspects of radiolabeling of antibodies, ranging from fast kinetic affibodies and nanobodies to slow kinetic intact mAbs. Herein, we focus on the most common approach which consists of first modification of the antibody with a chelator, and after eventual storage of the premodified molecule, radiolabeling as a second step. Other approaches are possible but have been excluded from this review. The review includes recent and representative examples from the literature highlighting which radiometal–chelator–antibody combinations are the most successful for in vivo application.