Figure 4.

(A,B) Positron emission tomography/computed tomography (PET/CT) images of ⁶⁸Ga-labeled anti-HER2 nanobody in patients with breast cancer showing uptake in tumor lesions. Images were obtained 90 min post injection. (A) A patient with invaded lymph nodes in the mediastinum and left hilar region. (B) A patient with bone metastasis in the pelvis. Data adapted from Keyaerts et al. (2016).³⁷ (C) ^99mTc-labeled anti-human PD-L1 nanobody can visualize human PD-L1⁺ melanoma tumors engrafted in athymic nude mice; however, no signal was observed in PD-L1⁻ tumors. Lack of signal in the tumors when an irrelevant control nanobody was used further confirmed the specificity of the observed signal. Single-photon emission computed tomography/CT images were obtained 1 h post injection. Data adapted from Broos et al. (2019).⁶⁴ (D,E) Complete Freund’s adjuvant was injected into the left paw. Twenty-four hours later, mice were imaged with ¹⁸F-labeled anti-mouse CD11b nanobody, which detected an influx of CD11b⁺ cells into the site of inflammation. Lymphoid organs were also detected (∼1–3% of lymphoid cells in secondary lymphoid organs are CD11b⁺). (E) ¹⁸F-2-fluoro-2-deoxyglucose (¹⁸F-FDG) failed to detect the influx of CD11b⁺ cells in the same model. PET/CT images were acquired 2 h post injection of the radiolabeled heavy-chain variable domain or ¹⁸F-FDG.

Data adapted from Rashidian et al. (2015).⁹