Purpose TEM-1 (tumor endothelial marker-1) is a single-pass transmembrane cell surface glycoprotein expressed at high levels by tumor vasculature and malignant cells. We aimed to perform a preclinical investigation of a novel anti-TEM-1 scFv-Fc fusion antibody, 1C1m-Fc, which was radiolabeled with 177 Lu for use in soft tissue sarcomas models. Methods 1C1m-Fc was first conjugated to p-SCN-Bn-DOTA using different excess molar ratios and labeled with 177 Lu. To determine radiolabeled antibody immunoreactivity, Lindmo assays were performed. The in vivo behavior of [177Lu]Lu-1C1m-Fc was characterized in mice bearing TEM-1 positive (SK-N-AS) and negative (HT-1080) tumors by biodistribution and single-photon emission SPECT/CT imaging studies. Estimated organ absorbed doses were obtained based on biodistribution results. Results The DOTA conjugation and the labeling with 177 Lu were successful with a radiochemical purity of up to 95%. Immunoreactivity after radiolabeling was 86% ± 4%. Biodistribution showed a specific uptake in TEM-1 positive tumor versus liver as critical non-specific healthy organ, and this specificity is correlated to the number of chelates per antibody. A 1.9-fold higher signal at 72 h was observed in SPECT/CT imaging in TEM-1 positive tumors versus control tumors. Conclusion TEM-1 is a promising target that could allow a theranostic approach to soft-tissue sarcoma, and 1C1m-Fc appears to be a suitable targeting candidate. In this study, we observed the influence of the ratio DOTA/antibody on the biodistribution. The next step will be to investigate the best conjugation to achieve an optimal tumor-to-organ radioactivity ratio and to perform therapy in murine xenograft models as a prelude to future translation in patients.

1C1m-Fc, an anti-tumor endothelial marker 1 (TEM-1) scFv-Fc fusion protein antibody, was previously successfully radiolabeled with 177Lu. TEM-1 specific tumor uptake was observed together with a non-saturation dependent liver uptake that could be related to the number of dodecane tetraacetic acid (DOTA) chelator per 1C1m-Fc. The objective of this study was to verify this hypothesis and to find the best DOTA per 1C1m-Fc ratio for theranostic applications. 1C1m-Fc was conjugated with six concentrations of DOTA. High-pressure liquid chromatography, mass spectrometry, immunoreactivity assessment, and biodistribution studies in mice bearing TEM-1 positive tumors were performed. A multi-compartment pharmacokinetic model was used to fit the data and a global pharmacokinetic model was developed to illustrate the effect of liver capture and immunoreactivity loss. Organ absorbed doses in mice were calculated from biodistribution results. A loss of immunoreactivity was observed with the highest DOTA per 1C1m-Fc ratio. Except for the spleen and bone, an increase of DOTA per 1C1m-Fc ratio resulted in an increase of liver uptake and absorbed dose and a decrease of uptake in tumor and other tissues. Pharmacokinetic models correlated these results. The number of DOTA per antibody played a determining role in tumor targeting. One DOTA per 1C1m-Fc gave the best pharmacokinetic behavior for a future translation of [177Lu]Lu-1C1m-Fc in patients.

Background: Angiogenesis plays an important role in head and neck squamous cell carcinoma (HNSCC) progression. This pilot study was designed to compare the distribution of 68 Ga-NODAGA-RGD PET/CT for imaging α v β 3 integrins involved in tumor angiogenesis to 18 F-FDG PET/CT in patients with HNSCC. Material and methods: Ten patients (aged 58.4 ± 8.3 years [range, 44-73 years], 6 males, 4 females) with a total of 11 HNSCC were prospectively enrolled. Activity mapping and standard uptake values (SUV) from both 68 Ga-NODAGA-RGD and 18 F-FDG PET/CT scans were recorded for primary tumor and compared with the Wilcoxon signed-rank test. The relation between the SUV of both tracers was assessed using the Spearman correlation. Results: All HNSCC tumors were visible with both tracers. Quantitative analysis showed higher 18 F-FDG SUV max in comparison to 68 Ga-NODAGA-RGD (14.0 ± 6.1 versus 3.9 ± 1.1 g/mL, p = 0.0017) and SUV mean (8.2 ± 3.1 versus 2.0 ± 0.8 g/mL, p = 0.0017). Both 18 F-FDG and 68 Ga-NODAGA-RGD uptakes were neither correlated with grade, HPV status nor p16 protein expression (p ≥ 0.17). Conclusion: All HNSCC tumors were detected with both tracers with higher uptake with 18 F-FDG, however. 68 Ga-NODAGA-RGD has a different spatial distribution than 18 F-FDG bringing different tumor information.

1C1m-Fc, a promising anti-TEM-1 DOTA conjugate, was labeled with 64Cu to target cancer cells for PET imaging and predicting the efficacy and safety of a previously studied [177Lu]Lu-1C1m-Fc companion therapy. DOTA-conjugated 1C1m-Fc was characterized by mass spectrometry, thin layer chromatography and immunoreactivity assessment. PET/CT and biodistribution studies were performed in human neuroblastoma xenografted mice. Absorbed doses were assessed from biodistribution results and extrapolated to 177Lu based on the [64Cu]Cu-1C1m-Fc data. The immunoreactivity was ≥ 70% after 48 h of incubation in serum, and the specificity of [64Cu]Cu-1C1m-Fc for the target was validated. High-resolution PET/CT images were obtained, with the best tumor-to-organ ratios reached at 24 or 48 h and correlated with results of the biodistribution study. Healthy organs receiving the highest doses were the liver, the kidneys and the uterus. [64Cu]Cu-1C1m-Fc could be of interest to give an indication of 177Lu dosimetry for parenchymal organs. In the uterus and the tumor, characterized by specific TEM-1 expression, the 177Lu-extrapolated absorbed doses are overestimated because of the lack of later measurement time points. Nevertheless, 1C1m-Fc radiolabeled with 64Cu for imaging would appear as an interesting radionuclide companion for therapeutic application with [177Lu]Lu-1C1m-Fc.

Background : Angiogenesis plays an important role in head and neck squamous cell carcinomas (HNSCC) progression. This pilot study was designed to compare the distribution of 68 Ga-NODAGA-RGD PET/CT for imaging α v β 3 integrins involved in tumor angiogenesis to 18 F-FDG PET/CT in patients with HNSCC. Material and methods : Ten patients (aged: 58.4 ± 8.3 years [range: 44–73 years], 6 males, 4 females) with a total of 11 HNSCC were prospectively enrolled. Activity mapping and standard uptake values (SUV) from both 68 Ga -NODAGA-RGD and 18 F-FDG PET/CT scans were recorded for primary tumor and compared with the Wilcoxon signed-rank test. The relation between the SUV of both tracers was assessed using the Spearman correlation. Results : All HNSCC tumors were visible with both tracers. Quantitative analysis showed higher 18 F-FDG SUV max in comparison to 68 Ga-NODAGA-RGD (14.0 ± 6.1 versus 3.9 ± 1.1 g/mL, p=0.0017) and SUV mean (8.2 ± 3.1 versus 2.0 ± 0.8 g/mL, p=0.0017). Both 18 F-FDG and 68 Ga-NODAGA-RGD uptake were neither correlated with grade, HPV nor p16 protein expression (p≥0.17). Conclusion : All HNSCC tumors were detected with both tracers with higher uptake with 18 F-FDG, however. 68 Ga-NODAGA-RGD has a different spatial distribution than 18 F-FDG bringing different tumor information.