A γ-AApeptide-Based Antibody-like Peptidomimetic for Enhanced EGFR-Targeted PET Imaging

Targeted imaging for the extracellular domain (ECD) of epidermal growth factor receptor (EGFR) is promising for early diagnosis and therapeutic applications toward cancers. Herein, we report the design of a γ-AApeptide-based antibody-like peptidomimetic as a radiotracer for EGFR-targeted positron emission tomography (PET) imaging. A dimeric cyclic γ-AApeptide (D1) was designed by dimerizing a previously reported EGFR-binding peptidomimetic ligand, resulting in a 6-fold enhancement in binding affinity (Kd = 0.11 μM) compared to its monomeric counterpart (M1, Kd = 0.67 μM). Both ligands were conjugated with chelators and radiolabeled with 64Cu to yield [64Cu]Cu-NOTA-M1 (monomer) and [64Cu]Cu-DOTA-D1 (dimer), respectively. In vivo PET imaging demonstrated that [64Cu]Cu-DOTA-D1 achieved significantly higher tumor uptake than [64Cu]Cu-NOTA-M1 in EGFR-positive tumor models (e.g., 10.83 ± 2.70 %ID/g vs 2.80 ± 0.72 %ID/g in U87 tumors at 4 h p.i.). Blocking and EGFR-negative control studies further confirmed the targeting specificity of [64Cu]Cu-DOTA-D1. Ex vivo biodistribution analysis showed consistent enhancement in tumor uptake (e.g., 7.94 ± 0.24 %ID/g vs 3.81 ± 0.44 %ID/g in U87 tumors at 48 h p.i.) for the dimeric tracer, accompanied by increased uptake in clearance organs. Overall, this work demonstrates that cyclic γ-AApeptides could serve as effective antibody-like peptidomimetics for EGFR targeting in vivo and provides a versatile strategy for developing peptidomimetic radiotracers for molecular imaging applications.