Synthesis and Preclinical Evaluation of Peptide Dimer-Based PET Tracers for Imaging VEGFR-2 Expression in Tumors

The vascular endothelial growth factor A (VEGF-A)/VEGF receptor 2 (VEGFR-2) signaling pathway is pivotal in regulating angiogenesis. We have synthesized a linear peptide-based VEGFR-2-targeted positron emission tomography (PET) tracer, but its target affinity and in vivo stability need further improvement. In this study, we developed two novel ⁶⁴Cu-labeled VEGFR-2-targeted PET dimer tracer [⁶⁴Cu]VEGF₂₂₁₅ and [⁶⁴Cu]VEGF₂₂₁₆ modified with a pegylated linear and branched linker, respectively, to optimize its pharmacokinetic properties and conducted a comprehensive preclinical assessment. Both tracers exhibited a radiochemical yield of over 95% and showed a high affinity for VEGFR-2 in U87MG cells. PET/CT imaging experiments indicated that [⁶⁴Cu]VEGF₂₂₁₅ exhibited a time-dependent accumulation in the U87MG tumor, with a maximum uptake of 4.95 ± 1.26 %ID/g at 24 h post-injection. In comparison, [⁶⁴Cu]VEGF₂₂₁₆ showed a consistently lower tumor uptake, peaking at only 3.07 ± 0.35 %ID/g. Blocking and biodistribution experiments further confirmed the specificity of [⁶⁴Cu]VEGF₂₂₁₅ for VEGFR-2. The favorable properties of [⁶⁴Cu]VEGF₂₂₁₅, including efficient synthesis, high tumor uptake, and rapid clearance from most normal organs, suggest it is a promising PET tracer for VEGFR-2-positive tumors.