[ ⁶⁸ Ga]Ga-DOTA-CEND1: A Novel PET Cyclic Peptide Tracer for Noninvasive Imaging of Neuropilin-1 Expression in Pan-Tumors

As a transmembrane glycoprotein overexpressed in various tumors, neuropilin-1 (NRP-1) is involved in tumor progression, angiogenesis, and immune evasion. This study developed a novel PET cyclic peptide radiotracer [⁶⁸Ga]Ga-DOTA-CEND1 for NRP-1 detection specifically and sensitively across multiple tumor types, potentially guiding personalized NRP-1 therapeutic regimens. NRP-1 expression was assessed and confirmed through immunohistochemical analysis of tissue microarrays, Western blot, immunohistochemistry, and immunofluorescence staining. The biochemical properties of the probe were investigated through radiochemical purity, lipid-water partition coefficient, pharmacokinetics, in vivo and in vitro stabilities, and biosafety studies. To determine diagnostic sensitivity and clinical applicability, cellular uptake assays, micro positron-emission tomography/computed tomography (PET/CT), blocking studies, and ex vivo biodistribution were performed in four NRP-1 positive tumor models (fibrosarcoma, TNBC, NSCLC, and pancreatic tumor) and one NRP-1-negative model (cervical tumor). [⁶⁸Ga]Ga-DOTA-CEND1 demonstrated >95% radiochemical purity, optimal pharmacokinetics, favorable hydrophilicity, robust in vivo and in vitro stability, and an ideal biosafety profile. Micro PET/CT at 1 h postinjection revealed significantly higher tumor uptake in NRP-1 positive tumor models than in the NRP-1 negative tumor model, while coinjection with nonradioactive CEND-1 significantly reduced tumor uptake, and tumor-to-muscle ratios aligned with NRP-1 expression levels, confirming the specificity and sensitivity of the radiotracer. As the first PET cyclic peptide radiotracer, [⁶⁸Ga]Ga-DOTA-CEND1 holds great potential for noninvasively detecting NRP-1 expression across tumor types, optimizing NRP-1 targeted therapy, and evaluating therapeutic responses.