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Background: In order to obtain an anti-CD20 conjugate to be used in future therapeutic studies with therapeutic radioisotopes, 67Ga-labeled antibody was prepared as a model of metal chelated immunoconjugate for preliminary dosimetric and biodistribution studies. Materials and Methods: Rituximab was labeled with [67Ga]-gallium chloride after residulation with freshly prepared cyclic DTPAdianhydride. The best results of the conjugation were obtained by the addition of 1 ml of a rituximab pharmaceutical solution (5 mg/ml, in phosphate buffer, pH=8) to a glass tube pre-coated with DTPAdianhydride (0.01 mg) at 25|o|C with continuous mild stirring for 30 min. The final isotonic 67Ga-DTPArituximab complex was checked by gel electrophoresis for radiolysis/chemolysis control. Radio-TLC was performed to ensure the formation of only one species. Preliminary in vivo studies in normal rat model were performed to determine the biodistribution of the radioimmunoconjugate up to 6 hours. Results: Radio-thin layer chromatography showed an overall radiochemical purity of 96-99% at optimized conditions (specific activity =300-500 MBq/mg, labeling efficiency 77%). Gel electrophoresis showed no protein cleavage after radiolabeling. Conclusion: Preliminary in vivo studies in normal rat model showed [67Ga]-DTPA-rituximab is a good probe for bio-dosimetry of therapeutic rituximab conjugates.
Iran. J. Radiat. Res., 2007 4 (4): 187-193

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Background: In order to diagnose the site of thrombi, radiolabeled streptokinase can be prepared. The radiolabeled compound can be used in imaging of thrombi in many cardiovascular diseases. Materials and Methods: Streptokinase was successively labeled with [67Ga]-gallium chloride using cyclic DTPA-dianhydride. The conjugation with DTPA was optimized for concentration, time and temperature followed by size exclusion chromatography using G-50 Sephadex. The radiochemical purity of the tracer was checked using HPLC and ITLC methods. The biodistribution studies were performed in normal rats up to 167 h using tissue counting and preliminary SPECT studies up to 2 h. Results: The radiolabeled enzyme was prepared in 60 minutes after incubation at room temperature, with the radiochemical purity of >95% (HPLC) and >99% (ITLC) methods. The radioactivity was accumulated in lung, intestine and liver as shown by scarification and SPECT (Single Photon Emission Computed Tomography) methods. Conclusion: Radiolabeled Streptokinase was prepared in suitable radiochemical purity and its biodistribution is comparable to other radiolabeled proteins. Further studies are required to investigate the imaging properties of the tracer in appropriate animal model. Iran. J. Radiat. Res., 2009 6 (4): 195-200