Radiolabeling of monoclonal anti-vascular endothelial growth factor receptor 1 (VEGFR 1) with (177)Lu for potential use in radioimmunotherapy.

The main goal of this study was to optimize the radioimmunoconjugation of monoclonal anti-vascular endothelial growth factor receptor 1 (VEGFR 1) with (177)Lu as a potential angiogenic molecular tracer for radioimmunotherapy (RIT). For a successful radiolabeling, we chose cysteine derivative DTPA-NCS as the bifunctional chelating agent and optimized radiolabeling condition with modifications on the factors such as the reaction time and molar ratio which are known to be very critical in radiolabeling. Under the optimized conditions, radiolabeling yield was greater than 99%. Immunoactivity of the radioimmunoconjugate was investigated using combinations of radioanalytical and bioanalytical techniques (ITLC-SG, Cyclone phosphorimager, and SDS-PAGE). For biological evaluations we carried out the cell binding assay and biodistribution study using mice bearing Calu6 non-small cell lung cancer xenografts. The biodistribution study showed high specificity in accumulating in tumor tissues where the tumor-to-blood ratio was 3.25:1 24h post-injection. In conclusion, the anti-VEGFR1 monoclonal antibody for angiogenesis targeting was effectively radioconjugated with (177)Lu. This radioimmunoconjugate is applicable to detect of angiogenesis sites in various diseases and treat tumors overexpressing VEGFR 1.