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

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