Advancements in nuclear imaging using radiolabeled nanobody tracers to support cancer immunotherapy

Abstract

The evolving landscape of cancer immunotherapy has revolutionized cancer treatment. However, the dynamic tumor microenvironment has led to variable clinical outcomes, indicating a need for predictive biomarkers. Noninvasive nuclear imaging, using radiolabeled modalities, has aided in patient selection and monitoring of their treatment response. This approach holds promise for improving diagnostic accuracy, providing a more personalized treatment regimen, and enhancing the clinical response. Nanobodies or single-domain antibodies, derived from camelid heavy-chain antibodies, allow early timepoint detection of targets with high target-to-background ratios. To date, a plethora of nanobodies have been developed for nuclear imaging of tumor-specific antigens, immune checkpoints, and immune cells, both at a preclinical and clinical level. This review comprehensively outlines the recent advancements in nanobody-based nuclear imaging, both on preclinical and clinical levels. Additionally, the impact and expected future advancements on the use of nanobody-based radiopharmaceuticals in supporting cancer diagnosis and treatment follow-up are discussed.

Keywords: cancer; diagnostics; immunotherapy; nanobodies; nuclear imaging.

Graphical Abstract

Figure 1.

Overview of different targeting moieties for PET and SPECT imaging. Their unique characteristics (molecular weight and optimal imaging timepoint) and matching radionuclides are presented. ⁶⁴Cu: copper-64; ¹⁸F: fluorine-18; Fab: antigen-binding fragment; ⁶⁸Ga: gallium-68; ¹¹¹In: indium-111; ¹³¹I: iodine-131; MW: molecular weight; Nb: nanobody; PET: positron emission tomography; ScFv: single-chain variable fragment; SPECT: single-photon emission computerized tomography; ^99mTc: technetium-99m; ⁸⁹Zr: zirconium-89. Created with BioRender.com.

Figure 2.

Examples of the clinical applicability of nanobody-based nuclear imaging of human epidermal growth factor receptor 2. (A) [⁶⁸Ga]Ga-NOTA-anti-HER2-sdAb (left) and [¹⁸F]FDG (right) maximum-intensity projection PET images of a patient with a HER2-positive (3+) invasive ductal breast carcinoma with [¹⁸F]FDG-avid lymph nodes in the mediastinum. The extent of disease to the cervical lymph nodes (arrow) was better delineated on [⁶⁸Ga]Ga-NOTA-anti-HER2-Nb as compared to [¹⁸F]FDG PET. (B) Representative maximum-intensity projection images of [¹⁸F]FDG PET (left) and ^99mTc-MIRC208 SPECT (right) in a patient with HER2 overexpression (3+). [¹⁸F]FDG: ¹⁸F-2-fluoro-2-deoxyglucose; ⁶⁸Ga: gallium-68; Nb: nanobody; PET: positron emission tomography; SPECT: single-photon emission computerized tomography; ^99mTc: techenetium-99m. Images have previously been published in an adapted form by: (A) JNM. Gondry et al. Phase II Trial Assessing the Repeatability and Tumor Uptake of [⁶⁸Ga]Ga-HER2 Single-Domain Antibody PET/CT in Patients with Breast Carcinoma. J Nucl Med. 2024; 65(2):178-184. © SNMMI [38]; and (B) Theranostics. Liqiang et al. HER2-targeted dual radiotracer approach with clinical potential for noninvasive imaging of trastuzumab-resistance caused by epitope masking. Theranostics. 2022; 12(12):5551-5563 [42], under a CC BY 4.0 license.

Figure 3.

Examples of the clinical applicability of nanobody-based molecular imaging of programmed death ligand 1 and the macrophage mannose receptor (CD206). (A) Axial SPECT/CT (top) and corresponding CT-imaging (bottom) of the programmed death ligand 1 (PD-L1) targeting and ^99mTc-labeled nanobody NM-01 in a patient with a high PD-L1-expressing primary non-small cell lung cancer (arrow). (B) Maximum-intensity projection [⁶⁸Ga]Ga-NOTA-anti-CD206 Nb (MMR3.49) images of a non-small cell lung cancer patient at 1.5 h post-injection. CT: computed tomography; ⁶⁸Ga: gallium-68; PET: positron emission tomography; SPECT: single-photon emission computerized tomography; ^99mTc: technetium-99m. Images have previously been published in an adapted form by: (A) JNM. Xing et al. Early Phase I Study of a ^99mTc-Labeled Anti-Programmed Death Ligand-1 (PD-L1) Single-Domain Antibody in SPECT/CT Assessment of PD-L1 Expression in Non-Small Cell Lung Cancer. J Nucl Med. 2019;60(9):1213-1220. © SNMMI [65]; and (B) JNM. Gondry et al. Phase I Study of [⁶⁸Ga]Ga-Anti-CD206-sdAb for PET/CT Assessment of Protumorigenic Macrophage Presence in Solid Tumors (MMR Phase I). J Nucl Med. 2023;64(9):1378-1384. © SNMMI [22], under a CC BY 4.0 license.

Figure 4.

Overview of radiolabeled nanobodies targeting different receptors within the TME. Both markers of immune cell populations and immune checkpoint molecules are presented. CTLA-4: Cytotoxic T-lymphocyte associated protein 4; ⁶⁴Cu: copper-64; ¹⁸F: fluorine-18; ⁶⁸Ga: gallium-68; ¹¹¹In: indium-111; LAG-3: Lymphocyte-activation gene 3; MHC-II: major histocompatibility complex II; MMR: macrophage mannose receptor; PD-1: Programmed cell death protein 1; PD-L1/2: Programmed death-ligand 1/2; PET: positron emission tomography; SIRPα: Signal regulatory protein α; SPECT: single-photon emission computerized tomography; TAM: tumor-associated macrophage; ^99mTc: technetium-99m; TCR: T-cell receptor; TIGIT: T cell immunoreceptor with immunoglobulin and ITIM domain; ⁸⁹Zr: zirconium-89. Created with BioRender.com.