Cumulated Activity Comparison of <sup>64</sup>Cu-/<sup>177</sup>Lu-Labeled Anti-Epidermal Growth Factor Receptor Antibody in Esophageal Squamous Cell Carcinoma Model.

Laffon, Eric; Thumerel, Matthieu; Jougon, Jacques; Marthan, Roger · J Nucl Med · 2017

basic_science · Level V

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Abstract

This work aimed at estimating the kinetic parameters, and hence cumulated activity (A<sub>C</sub>), of a diagnostic/therapeutic convergence radiopharmaceutical, namely <sup>64</sup>Cu-/<sup>177</sup>Lu-labeled antibody (<sup>64</sup>Cu-/<sup>177</sup>Lu-cetuximab), that acts as anti-epidermal growth factor receptor. <b>Methods:</b> In mice bearing esophageal squamous cell carcinoma tumors, to estimate uptake (K), release rate constant (k<sub>R</sub>), and hence A<sub>C</sub>, a kinetic model analysis was applied to recently published biodistribution data of immuno-PET imaging with <sup>64</sup>Cu-cetuximab and of small-animal SPECT/CT imaging with <sup>177</sup>Lu-cetuximab, including blood and TE-8 tumor. <b>Results:</b> K, k<sub>R</sub>, and A<sub>C</sub> were estimated to be 0.0566/0.0593 g⋅h<sup>-1</sup>⋅g<sup>-1</sup>, 0.0150/0.0030 h<sup>-1</sup>, and 2.3 × 10<sup>10</sup>/4.1 × 10<sup>12</sup> disintegrations (per gram of TE-8 tumor), with an injected activity of 3.70/12.95 MBq, for <sup>64</sup>Cu-/<sup>177</sup>Lu-cetuximab, respectively. <b>Conclusion:</b> A model is available for comparing kinetic parameters and A<sub>C</sub> of the companion diagnostic/therapeutic <sup>64</sup>Cu-/<sup>177</sup>Lu-cetuximab that may be considered as a step for determining whether one can really use the former to predict dosimetry of the latter.

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