Preparation and Preliminary Evaluation of a Novel 68 Ga-Labeled Linear Peptide PET Probe Targeting Nectin-4

Objectives: Nectin-4 has been successfully used as a target for tumor therapy. Although several bicyclic peptides and antibodies, Nectin-4 positron emission tomography (PET) probes, have been reported for tumor imaging and expression detection, their production costs or pharmacokinetics still need further improvement. This study developed a novel linear peptide PET probe for rapid examination of Nectin-4-related tumors. Methods: [⁶⁸Ga]Ga-NOTA-SP was prepared by a one-step chelation reaction, and its quality control was carried out by using radio-high-performance liquid chromatography and thin-layer chromatography. Molecular docking was used to predict the predominant binding of NOTA-SP to Nectin-4. Cell experiments using SW780 cells and PET/computed tomography (CT) imaging, using the SW780 tumor model, were performed to assess the specific binding and targeting ability of [⁶⁸Ga]Ga-NOTA-SP to Nectin-4. Normal BALB/c mice were used to investigate the plasma concentration-time curves. Results: Under optimal labeling conditions, the labeling efficiency of [⁶⁸Ga]Ga-NOTA-SP can reach above 95%, with a molar-specific activity of 2.45 MBq/nmol and high in vitro stability. The high specificity of [⁶⁸Ga]Ga-NOTA-SP to Nectin-4 is demonstrated by molecular docking and cell uptake experiment, showing a binding energy of -5.4 kcal/mol and K_d value of 2.483 nM, which was further confirmed by PET-CT imaging. Conclusions: [⁶⁸Ga]Ga-NOTA-SP using a linear peptide as a vector shows favorable pharmacokinetics and specific targeting ability to Nectin-4, enabling rapid tumor mouse model imaging. It would be a promising PET/CT imaging probe for optimizing Nectin-4-related tumor diagnoses and therapy.