Development and evaluation of ⁶⁸Ga-DOTA-EP-1: A novel PET tracer targeting EpCAM for malignant tumor diagnosis

EpCAM is overexpressed in solid tumors and is a promising pan-tumor imaging target, yet clinically applicable PET tracers are limited. We developed and evaluated a novel EpCAM-targeted tracer, ⁶⁸Ga-DOTA-EP-1. The peptide sequence EP-1 (YEVHTYYLD) was previously identified as an EpCAM-binding ligand via high-throughput bi-functional microarray screening. Based on this scaffold, we performed chemical modification by conjugating a DOTA chelator via an Acp linker to enable ⁶⁸Ga radiolabeling for PET imaging. After labeling, stability, lipophilicity, protein binding, and specificity were evaluated in EpCAM-positive and -negative cell lines. In vivo PET imaging, biodistribution, immunohistochemistry, and toxicity were performed in tumor-bearing mice, followed by a preliminary clinical study. ⁶⁸Ga-DOTA-EP-1 exhibited high radiochemical purity and excellent stability. Cellular uptake was significantly higher in EpCAM-positive cells (P < 0.05), with high binding affinity confirmed by blocking and IC₅₀ assays. PET imaging showed markedly higher uptake in EpCAM-positive xenografts, significantly reduced by blocking. Preliminary clinical imaging demonstrated favorable safety and clear visualization of hepatic metastases. These findings suggest that ⁶⁸Ga-DOTA-EP-1 has the potential to serve as an EpCAM-targeted PET tracer with favorable specificity and a promising safety profile for further clinical evaluation.