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Abstract: Aim: PR81 is a monoclonal antibody that binds with high affinity to MUC1 antigen that is over expressed in 80% of breast cancers. In this study, we developed a method for indirect labeling of PR81 with lutetium-177 and performed all preclinical qualifications in production of a biologic agent for radioimmunotherapy of breast cancer. Materials and Methods: The radiochemical purity and in vitro stability of 177Lu labeled PR81 was determined by instant thin layer chromatography. The immunoreactivity and cell toxicity of the complex were tested on MCF7 cell line. The biodistribution and scintigraphy studies were performed in BALB/c mice with breast tumor. Results: The radiochemical purity was 91.2±3.8% after 2 h. The in vitro stabilities in phosphate buffer and human blood serum were 83.1±3.4% and 76.2±3.6% at 96 h, respectively. The immunoreactivity of the complex was 83.4±2.4%. The cell toxicity study showed that the complex inhibited 85.2±3.4% growth of MCF7 cells at a concentration of 2500 ng/ml after 96 h. The biodistribution and scintigraphy studies showed the accumulation of the complex at the site of tumors with high sensitivity and specificity. Conclusion: The results showed that one may consider 177Lu-DOTA–PR81 as a potential radiopharmaceutical for therapy of human breast cancer, which needs further investigations. [Copyright &y& Elsevier]

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]

Abstract: Human epithelial mucin, MUC1, is commonly overexpressed in adenocarcinoma that includes more than 80% of breast cancers. The PR81 is a murine anti-MUC1 monoclonal antibody (MAb) that was prepared against the human breast cancer. We developed an indirect method for labeling of this antibody with 99mTc in order to use the new preparation in immunoscintigraphy studies of BALB/c mice bearing breast tumors. The 99mTc–PR81 complex was prepared using the HYNIC as a chelator and tricine as a coligand. The labeling efficiency determined by instant thin-layer chromatography (ITLC) was 89.2%±4.7%, and radiocolloides measured by cellulose nitrate electrophoresis were 3.4%±0.9%. The in vitro stability of labeled product was determined at room temperature by ITLC and in human serum by gel filtration chromatography — 88.3%±4.6% and 79.8%±5.7% over 24 h, respectively. The integrity of labeled MAb was checked by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis, and no significant fragmentation was seen. The results of cell binding studies showed that both labeled and unlabeled PR81 were able to compete for binding to MCF 7 cells. Biodistribution studies performed in female BALB/c mice with breast tumor xenografts at 4, 16 and 24 h after the 99mTc-HYNIC-PR81 injection demonstrated a specific localization of the compound at the site of tumors and minimum accumulation in non target organs. The tumor imaging was performed in BALB/c mice with breast xenograft tumors at 4, 8, 12, 16, 20, 24, 28, 32 and 36 h after the complex injection. The tumors were visualized with high sensitivity after 8 h. The findings showed that the new radiopharmaceutical is a promising candidate for radioimmunoscintigraphy of the human breast cancer. [Copyright &y& Elsevier]