Radiolabeled Angiopep-2 Peptide Vector as a Preclinical Platform for Blood-Brain Barrier Targeting: Synthesis,...

Brain tumor therapy remains limited by the blood-brain barrier (BBB), which restricts drug access. BBB-penetrating peptides offer a promising strategy for delivering therapeutic and diagnostic payloads. Angiopep-2 is a well-established vector, yet novel radioconjugates based on this vector remain of interest. We report the synthesis and evaluation of DOTA-Angiopep-2 for radiolabeling with Lutetium-177 (¹⁷⁷Lu) and Terbium-161 (¹⁶¹Tb). Notably, ¹⁷⁷Lu serves as a β- and γ-emitter, whereas ¹⁶¹Tb is an Auger and β-emitter; both are utilized in therapy and SPECT imaging. Peptides were synthesized via solid-phase peptide synthesis. Cytotoxicity assays in T98 glioblastoma cells showed that Angiopep-2 is well-tolerated, maintaining ~100% viability at 20 μM and a moderate decline up to 100 μM. Radiolabeling achieved yields > 95% with excellent radiochemical stability at room temperature for up to 10 days and moderate stability in the presence of human serum. Biodistribution in healthy CFW mice showed a brain-associated radioactivity of 0.24% ± 0.05% IA/g at 5 min p.i. and a 12-fold increase in the brain-to-blood ratio (0.028-0.339) by 60 min p.i. These results support DOTA-Angiopep-2 as a versatile platform for radionuclide delivery and a potential candidate for future glioma-targeted studies. Further studies in tumor-bearing models are ongoing to evaluate therapeutic efficacy and translational potential.