Preparation, quality control and biodistribution assessment of [111 In]In-DOTA-PR81 in BALB/c mice bearing breast tumors.

Introduction In this study, [111 In]In-DOTA-PR81 was developed and its preliminary preclinical qualifications were assessed for SPECT imaging of breast cancer. Methods DOTA-NHS-ester was practiced and successively purified by molecular filtration. The chelate:mAb ratio was determined by spectrophotometry. DOTA-PR81 was radiolabeled with In-111 and its radiochemical yield, in vitro stability, in vitro internalization and immunoreactivity tests were performed. SPECT imaging and tissue counting were applied to evaluate the tissue distribution of [111 In]In-DOTA-hIgG and [111 In]In-DOTA-PR81 in BALB/c mice bearing breast tumors. Results The radiochemical yield of [111 In]In-DOTA-PR81 complex was >95.0±0.5% (ITLC) and the specific activity was 170±44 MBq/mg. Conjugation reaction resulted in the average number of chelators attached to a mAb (c/a) of 3.4±0.3:1. The radioimmunoconjugate showed immunoreactivity towards MCF7 cell line and MUC1 antigen while its significant in vitro and in vivo stability were investigated over 48 hours respectively (93.0±1.2% in PBS and 84.0±1.3% in human serum). The peak concentration of internalized activity of [111 In]In-DOTA-PR81 was between 4 to 6 h. In comparison to control probes, the complex was accumulated with high specificity and sensitivity at the tumor site. Conclusion Achieved results indicated that [111 In]In-DOTA-PR81 could be contemplated as an appropriate radiotracer for prognostic imaging of antigens in oncology.