Gallium-68 Labeled Positron Emission Computed Tomography Tracer Targeting Glypican-3 with High Contrast for Hepatocellular Carcinoma Imaging

Hepatocellular carcinoma (HCC) represents the predominant form of primary liver cancer, yet early, precise, and noninvasive detection continues to pose a considerable clinical challenge. Glypican-3 (GPC3), a membrane-bound proteoglycan, is markedly overexpressed in most HCC cases, while exhibiting low expression in normal and hepatitis-affected liver tissues. Given its crucial role in malignant transformation and tumor progression, GPC3 emerges as a compelling target for imaging. In this study, we developed and evaluated 2 ⁶⁸Ga-labeled GPC3-targeted positron emission tomography (PET) probes, each incorporating either polyethylene glycol (PEG) or 4-(<i>p</i>-methylphenyl)butanoic acid (an albumin-binding moiety). Comparative analyses revealed that ⁶⁸Ga-ALB-GBP, which includes the albumin-binding moiety, exhibited superior in vivo stability, enhanced tumor uptake, and an improved tumor-to-liver ratio relative to ⁶⁸Ga-PEG₂-GBP in subcutaneous HCC mouse models. Micro-PET/computed tomography imaging of orthotopic liver cancer with ⁶⁸Ga-ALB-GBP demonstrated a tumor-to-liver ratio of 2.29 ± 0.13 and a tumor-to-muscle ratio of 13.03 ± 1.63 at 3 h postinjection, outperforming the performance of the clinically used ¹⁸F-fluorodeoxyglucose PET imaging. These findings suggest that ⁶⁸Ga-ALB-GBP is a promising diagnostic tool for HCC and a strong candidate for clinical translation with potential utility in both diagnostic and therapeutic settings. Moreover, the incorporation of an albumin-binding moiety into PET tracers significantly extends blood circulation time, thereby enhancing bioavailability and facilitating high-contrast PET imaging.