⁶⁴Cu-Based Pretargeted Immuno-Positron Emission Tomography and Near-Infrared Fluorescence Imaging of the Vascular Endothelial Growth Factor

Pretargeted immuno-positron emission tomography (PET)/near-infrared fluorescence (NIRF) using bioorthogonal chemistry between radioisotope- or fluorophore-labeled Reppe anhydrides and vascular endothelial growth factor (VEGF)-specific monoclonal antibody bevacizumab–tetrazine conjugates was developed. The pretargeting approach provided a high target-to-background contrast. An in vivo investigation clearly indicated the suitability of the 64Cu-radiolabeled Reppe anhydride for pretargeted PET imaging of VEGF-expressing colorectal tumors. The radiation exposure to healthy tissues decreased as a result of the rapid elimination of the PET probe. Pretargeted NIRF imaging was also used to visualize the VEGF expression in HCT116 tumors using bevacizumab–tetrazine/cyanine 5-labeled Reppe anhydride chemistry