68Ga- and 211At-Labeled RGD Peptides for Radiotheranostics with Multiradionuclides

Probes for radiotheranostics could be produced by introducing radionuclides with similar chemical characteristics into the same precursors. We recently developed an ²¹¹At-labeled RGD peptide and a corresponding radioiodine-labeled RGD peptide. Both labeled peptides accumulated in large quantities in the tumor with similar biodistribution, demonstrating their usefulness for radiotheranostics. In this study, we hypothesized that probes for radiotheranostics combined with multiradionuclides, such as ⁶⁸Ga and ²¹¹At, have useful clinical applications. New radiolabeled RGD peptide probes were synthesized via a molecular design approach, with two labeling sites for metal and halogen. These probes were evaluated in biodistribution experiments using tumor-bearing mice. [⁶⁷Ga]Ga-DOTA-c[RGDf(4-I)K] ([⁶⁷Ga]4), Ga-DOTA-[¹²⁵I]c[RGDf(4-I)K] ([¹²⁵I]4), and Ga-DOTA-[²¹¹At]c[RGDf(4-At)K] ([²¹¹At]7) showed similar biodistribution, with high and equivalent accumulation in tumors. These results indicate the usefulness of these probes in radiotheranostics with multiradionuclides, such as a radiometal and a radiohalogen, and they could contribute to a personalized medicine regimen.