[Direct and indirect labeling with 99mTc of an antireceptor monoclonal antibody of EGF]. / Marcaje directo e indirecto con 99mTc de un anticuerpo monoclonal antireceptor del factor de crecimiento epidérmico.

INTRODUCTION: Radiolabeled monoclonal antibodies (MAbs) have been a useful tool for diagnostic imaging and therapy in Oncology. The aim of this study was to carry out the indirect 99mTc radiolabeling of ior egf/r3, monoclonal antibody (MAb) specific for epidermal growth factor (EGF) receptor, and the comparison with a direct 99mTc radiolabeling approach. MATERIAL AND METHODS: Cyclic anhydride of the diethylenetriaminepentaacetic acid (ADTPA) was employed as bifunctional chelating agent in the indirect monoclonal antibody radiolabeling and it was coupled to MAb at molar ratios of 20:1, 50:1 and 200:1 (ADTPA:MAb). For the direct radiolabeling, the reduction of MAb was performed with 2-mercaptoethanol (2ME), based on Schwarz's method. Biological activity was measured by Flow Cytometry. Biodistribution studies were performed at 1, 3 and 24 h after injection of the radiolabeled antibody in Wistar rats. RESULTS: After 30 min of 99mTc radiolabeling of the ior egf/r3 MAb, the radiochemical purity values were between 80.0 +/- 1.8 and 90.0 +/- 1.2 % for the indirect method using ADTPA, while it was 94.8 +/- 1.6 % for the direct approach using 2ME. Stability of the 99mTc-radiopharmaceuticals was similar for both methods. The biological activity was similar for both antibody formulations. There were no significant differences for the biodistribution to normal organs for both radiolabeled antibodies. CONCLUSIONS: Use of ADTPA was shown to be an efficient method for the 99mTc labeling of the monoclonal antibody ior egf/r3. Radiolabeling using 2ME showed higher radiochemical purity.

Marcaje directo e indirecto con 99mTc de un anticuerpo monoclonal antireceptor del factor de crecimiento epidérmico / Direct and indirect labeling with 99mTc of an antireceptor monoclonal antibody of EGF

Introducción: La utilización de anticuerpos monoclonales (AcMs) radiomarcados ha sido una valiosa herramienta dentro de la Oncología, tanto para el diagnóstico por medio de imágenes como para la terapia. Constituye el objetivo fundamental del presente trabajo la radiomarcación indirecta con 99mTc del anticuerpo monoclonal (AcM) ior egf/r3, el cual es específico para el receptor del factor de crecimiento epidérmico (FCE), y la comparación de este procedimiento con un método directo. Material y métodos: Para el marcaje indirecto del anticuerpo se empleó el anhidrido cíclico del ácido dietilentriaminopentaacético (ADTPA) como agente quelantante bifuncional, realizándose la conjugación al AcM ior egf/r3 a relaciones molares de 20:1, 50:1 y 200:1 (ADTPA:AcM). El radiomarcaje directo del anticuerpo se basó en el método de Schwarz, utilizando el 2-mercaptoetanol (2ME) como agente reductor. La actividad biológica se determinó por citometría de flujo. Los estudios de biodistribución se realizaron a 1, 3 y 24 h de inyectado el anticuerpo radiomarcado en ratas Wistar. Resultados: A los 30 minutos de radiomarcado el AcM con 99mTc, se encontraron valores de pureza radioquímica entre 80,0 ± 1,8 y 90,0 ± 1,2 % mediante el ADTPA; mientras que con el 2ME, la pureza radioquímica fue de 94,8 ± 1,6. Se encontró similitud tanto en la estabilidad de los radiofármacos obtenidos por ambos métodos, como en la actividad biológica resultante. Los estudios de biodistribución muestran cierto nivel de captación en hígado, sangre y bazo, que no resultaron significativos. Conclusiones: Se demostró que el AcM ior egf/r3 puede ser radiomarcado de manera eficiente por vía indirecta, utilizando el ADTPA como agente quelatante bifuncional. Se obtuvo una mayor pureza radioquímica mediante el radiomarcaje con 2ME

Introduction: Radiolabeled monoclonal antibodies (MAbs) have been a useful tool for diagnostic imaging and therapy in Oncology. The aim of this study was to carry out the indirect 99mTc radiolabeling of ior egf/r3, monoclonal antibody (MAb) specific for epidermal growth factor (EGF) receptor, and the comparison with a direct 99mTc radiolabeling approach. Material and methods: Cyclic anhydride of the diethylenetriaminepentaacetic acid (ADTPA) was employed as bifunctional chelating agent in the indirect monoclonal antibody radiolabeling and it was coupled to MAb at molar ratios of 20:1, 50:1 and 200:1 (ADTPA:MAb). For the direct radiolabeling, the reduction of MAb was performed with 2-mercaptoethanol (2ME), based on Schwarz's method. Biological activity was measured by Flow Cytometry. Biodistribution studies were performed at 1, 3 and 24 h after injection of the radiolabeled antibody in Wistar rats. Results: After 30 min of 99mTc radiolabeling of the ior egf/r3 MAb, the radiochemical purity values were between 80.0 ± 1.8 and 90.0 ± 1.2 % for the indirect method using ADTPA, while it was 94.8 ± 1.6 % for the direct approach using 2ME. Stability of the 99mTc-radiopharmaceuticals was similar for both methods. The biological activity was similar for both antibody formulations. There were no significant differences for the biodistribution to normal organs for both radiolabeled antibodies. Conclusions: Use of ADTPA was shown to be an efficient method for the 99mTc labeling of the monoclonal antibody ior egf/r3. Radiolabeling using 2ME showed higher radiochemical purityIntroduction: Radiolabeled monoclonal antibodies (MAbs) have been a useful tool for diagnostic imaging and therapy in Oncology. The aim of this study was to carry out the indirect 99mTc radiolabeling of ior egf/r3, monoclonal antibody (MAb) specific for epidermal growth factor (EGF) receptor, and the comparison with a direct 99mTc radiolabeling approach. Material and methods: Cyclic anhydride of the diethylenetriaminepentaacetic acid (ADTPA) was employed as bifunctional chelating agent in the indirect monoclonal antibody radiolabeling and it was coupled to MAb at molar ratios of 20:1, 50:1 and 200:1 (ADTPA:MAb). For the direct radiolabeling, the reduction of MAb was performed with 2-mercaptoethanol (2ME), based on Schwarz's method. Biological activity was measured by Flow Cytometry. Biodistribution studies were performed at 1, 3 and 24 h after injection of the radiolabeled antibody in Wistar rats. Results: After 30 min of 99mTc radiolabeling of the ior egf/r3 MAb, the radiochemical purity values were between 80.0 ± 1.8 and 90.0 ± 1.2 % for the indirect method using ADTPA, while it was 94.8 ± 1.6 % for the direct approach using 2ME. Stability of the 99mTc-radiopharmaceuticals was similar for both methods. The biological activity was similar for both antibody formulations. There were no significant differences for the biodistribution to normal organs for both radiolabeled antibodies. Conclusions: Use of ADTPA was shown to be an efficient method for the 99mTc labeling of the monoclonal antibody ior egf/r3. Radiolabeling using 2ME showed higher radiochemical purity

2,3,5,6-Tetrafluorophenyl N-(S-benzoylthioacetyl)glycylglycyl- p-aminobenzoate, a heterobifunctional (99m)Tc ligand for precomplexed antibody labeling.

Heterobifunctional (99m)Tc ligands are useful for antibody labeling using the precomplexation route. The aim of this work was to synthesize a ligand, which has sufficient chemical stability to be complexed with (99m)Tc without inactivating the reactive conjugation group. Using 2,3,5,6-tetrafluorophenyl N-(S-benzoylthioacetyl)glycylglycyl-p-aminobenzoate (OC2) >60% of the (99m)Tc complex was obtained at 80 degrees C in 20 min, which was separated from the free ligand and impurities by HPLC. After solvent evaporation, (99m)Tc-OC2 was conjugated with the monoclonal antibody mAb425 in 50% radiochemical yield. In all, the labeling method required about 1 h preparation time. The immunoreactive fraction of the (99m)Tc-OC2 mAb425 conjugate was 81%, indicating preserved binding capability after conjugation. Compared to recently described methods, which need in situ activation of the (99m)Tc complex, the application of OC2 saved time and reduced the number of manipulations with radioactive material.