Chemically Evolved Integrin α5β1-Targeted Peptide PET Tracers for Orthotopic Pancreatic Ductal Adenocarcinoma Detection.

Pancreatic ductal adenocarcinoma (PDAC) remains a lethal malignancy characterized by a dense desmoplastic microenvironment. Integrin α5β1 mediates tumor-stroma interactions via fibronectin binding and is markedly upregulated in PDAC, making it an attractive drug target; however, α5β1-targeted radiotracers for PDAC imaging remain scarce. Here, we developed α5β1-targeted peptide radiotracers to evaluate their preclinical potential for PET/CT imaging of PDAC. Using the fibronectin-derived peptide AV3 (RYYRITY) as a scaffold, we performed stepwise chemical evolution through alanine scanning and noncanonical amino acid engineering, leading to a focused library of 15 structurally evolved AV3 analogues radiolabeled with gallium-68. The radiotracers were systematically evaluated by in vitro assays, microPET/CT imaging, and ex vivo biodistribution. Among them, [68Ga]Ga-HKA-008 exhibited enhanced stability, increased tumor uptake, and improved retention compared with [68Ga]Ga-DOTA-AV3. Notably, [68Ga]Ga-HKA-008 demonstrated notable uptake in orthotopic pancreatic tumors in vivo, suggesting the feasibility of α5β1-targeted radiotracers for PDAC imaging.