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

Abstract

Breast cancer radioimmunoscintigraphy targeting HER2/neu expression is a growing field of work in nuclear medicine research. In this study, trastuzumab was successively labeled with [(67)Ga] GaCl3 after conjugation with DOTA-NHS-ester. The conjugates were purified by molecular filtration, the average number of DOTA conjugated per mAb was calculated and total concentration was determined by spectrophotometric method. DOTA-Trastuzumab was labeled with (67)Ga. Radiochemical purity, integrity of protein after radiolabeling and stability of (67)Ga-DOTA-Trastuzumab were determined followed by biodistribution studies in wild-type rats (30 ± 5.5 μCi, 2, 4 and 24 h 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 was 5.8:1. The final compound was stable in presence of PBS at 37ºC and room temperature. The sample was showed to have similar patterns of migration in the gel electrophoresis similar to the native protein. The accumulation of the radiolabeled antibody in liver, spleen, kidney, heart and other tissues demonstrates. (67)Ga-DOTA-Trastuzumab was prepared as a surrogate for important clinically applicable radionuclides 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 treatment studies and follow-up of HER2 expression in oncology.