Production and Quality Control of [67Ga]-DOTA-trastuzumab for Radioimmunoscintigraphy

Breast cancer radioimmunoscintigraphy targeting HER2/neu expression is a growing fieldof work in nuclear medicine research. In this study, trastuzumab was successively labeledwith [67Ga] GaCl3 after conjugation with DOTA-NHS-ester.The conjugates were purified by molecular filtration, the average number ofDOTA conjugated per mAb was calculated and total concentration was determined byspectrophotometric method. DOTA-Trastuzumab was labeled with 67Ga. Radiochemicalpurity, integrity of protein after radiolabeling and stability of 67Ga-DOTA-Trastuzumab weredetermined followed by biodistribution studies in wild-type rats (30 ± 5.5 μCi, 2, 4 and 24h p.i.).The radioimmunoconjugate was prepared with a radiochemical purity of higher than 95%(RTLC). The average chelate to antibody ratio (c/a) for the conjugate used in this study was5.8:1. The final compound was stable in presence of PBS at 37ºC and room temperature. Thesample was showed to have similar patterns of migration in the gel electrophoresis similarto the native protein. The accumulation of the radiolabeled antibody in liver, spleen, kidney,heart and other tissues demonstrates.67Ga-DOTA-Trastuzumab was prepared as a surrogate for important clinically applicableradionuclides used in SPECT and PET including In-111 and Cu-64 as a model of radiolabeling.It is also a potential compound for molecular imaging of SPECT for diagnosis and treatmentstudies and follow-up of HER2 expression in oncology.