Design, Synthesis, and Evaluation of 99mTc-Labeled PSMA-Targeting Dimeric Tracers: Comparison of Glutamate−Urea−Lysine (EuK) and Aminoadipic Acid−Urea−Lysine (AuK) Targeting Groups

Abstract In clinical practice of prostate cancer (PCa) management, the high renal uptake of prostate-specific membrane antigen (PSMA)-targeted radiotracers remains a significant concern. To address this challenge, the study systematically evaluated molecular modification strategiestargeting moieties, linker types, and coligand compositionsfor their effects on tracer pharmacokinetics. Among candidates, [99mTc]Tc-EuK2-LPRO-HYNIC-EDDA was the most promising for single-photon emission computed tomography (SPECT) imaging. It binds PSMA stably with nanomolar affinity (Kd = 16.28 nM), and the high blocking efficiency in vitro and in vivo subsequently confirmed excellent targeting specificity. The tracer cleared rapidly from nontarget organs, effectively mitigating renal accumulation and giving high target-to-background ratios. Crucially, high-contrast SPECT/CT images obtained 2−6 h post-injection indicate clinical promise for routine and delayed PCa imaging. Additionally, density functional theory (DFT) and molecular dynamics (MD) simulations provided critical theoretical insights into coordination structure, ligand−protein interaction mechanisms, and correlations between conformational differences and biological activity.