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Abstract: Introduction: In the present study, Herceptin was labeled with lutetium-177 via DOTA, and the necessary preclinical quality control tests (in vitro and in vivo) were performed to evaluate its use as a radioimmunotherapy agent. Material and Methods: Herceptin was conjugated to DOTA as a chelator in three different conjugation buffers (ammonium acetate, carbonate and HEPES buffer); each of the resulting conjugates was compared with respect to in vitro characteristics such as number of chelates per antibody, incorporated activity, immunoreactivity and in vitro stability in PBS buffer and blood serum. The biodistribution study and gamma camera imaging were performed in mice bearing breast tumors. To assess the therapeutic effects of 177Lu-Herceptin, cytotoxicity was investigated for 7 days in a SKBr3 breast cancer cell line. Results: Carbonate buffer was the best conjugation buffer (number of chelates per antibody: 6; incorporated activity: 81%; immunoreactivity: 87%; buffer stability: 86%; serum stability: 81%, after 4 days). The efficient tumor uptake observed in the biodistribution studies was consistent with the gamma camera image results. At a concentration of 4 μg ml−1, 177Lu-Herceptin (surviving cells: 5±0.6% of the total cells) of the total cells corresponded to an approximately eightfold increase in cytotoxicity in comparison to unmodified Herceptin (surviving cells: 43±3.9%). Conclusion: The new complex described herein could be considered for further evaluation in animals and potentially in humans as a radiopharmaceutical for use in the radioimmunotherapy of breast cancer. These results may be important for patients who cannot tolerate the therapeutic dosage of Herceptin currently used because of heart problems. [Copyright &y& Elsevier]

Abstract: Aim: Trastuzumab is a monoclonal antibody that is used in treating breast cancer. We labeled this monoclonal antibody with lutetium-177 and performed in vitro quality control tests as a first step in the production of a new radiopharmaceutical. Material and Methods: Trastuzumab was labeled with lutetium-177 using DOTA as chelator. Radiochemical purity and stability in buffer and human blood serum were determined using thin layer chromatography. Immunoreactivity and toxicity of the complex were tested on MCF7 breast cancer cell line. Results: The radiochemical purity of the complex was 96±0.9%. The stabilities in phosphate buffer and in human blood serum at 96 h postpreparation were 93±1.2% and 85±3.5%, respectively. The immunoreactivity of the complex was 89±1.4%. At a concentration of 1 nM, the complex killed 70±3% of MCF7 cells. At 1.9 nM, 90±5% of the cells were killed. Conclusions: The results showed that the new complex could be considered for further evaluation in animals and possibly in humans as a new radiopharmaceutical for use in radioimmunotherapy against breast cancer. [Copyright &y& Elsevier]