Design and Bio.evaluation of 64Cu-NOTA-Herceptin for Tumor Targeted Micro-PET Imaging

The precursor compound 2-(p-thiocyanatobenzyl). 1,4,7-triazacyclononane. 1,4,7-triacetic acid-Herceptin(NOTA-Herceptin) was synthesized by the nucleophilic addition reaction of Herceptin and bi-functional chelator NCS-Bz-NOTA. The original Herceptin and NOTA-Herceptin conjugate were investigated by UV-Vis and MALDI-TOF mass spectra. The average number of chelators per Herceptin for the conjugated used in this study was 5.4. The enzyme. linked immunosorbent assay(ELISA) was conducted to compare the biological activity of original Herceptin and NOTA. Herceptin. NOTA. Herceptin kept high immunoreactivity towards HER2 antigen. Then, the PET radio. nuclide Cu-64(T-1/2 = 12.7 h) was labeled to got the novel tumor Immuno-Theranostics probe Cu-64-NOTA-Herceptin. The labeling efficiency of Cu-64-NOTA. Herceptin was tested by Radio-TLC/HPLC. The radiolabeling yield was over 90%, the radio chemical purity was over 98% after PD-10 column purification and the specific activity was 185 MBq/nmol. The immune reactivity and specific activity of radiolabeled Herceptin with HER2 antigen were performed by HER2 positive NCI-N87 cell line and HER2 negative BGC823 cell line. Micro. PET imaging of BGC823 tumor. bearing nude mice revealed that tumor up-take of Cu-64-NOTA-Herceptin got a gradual accumulation from 4 h to 60 h after intravenous injection of 7.4 MBq radiolabeled Herceptin. Uptake in the tumor was clearly visualized by emission computed tomography. Cu-64-NOTA. Herceptin owns a great potential for molecular imaging of PET for diagnosis and follow-up of HER2 expression.