Development of a ¹⁷⁷ Lu-Labeled Glypican-3-Targeted Antibody Radiopharmaceutical for Adjuvant Radionuclide Therapy Following Hepatocellular Carcinoma Resection

Background: Hepatocellular carcinoma (HCC) remains the major cause of cancer-related mortality worldwide due to high postoperative recurrence rates and limited treatment options for minimal residual disease (MRD). Methods: In this study, glypican-3 (GPC3)-targeted radiopharmaceutical, 177 Lu-DOTA-GPC3, was developed and evaluated as a potential adjuvant targeted radionuclide therapy for HCC. The anti-GPC3 monoclonal antibody was conjugated with DOTA and radiolabeled with 177 Lu under systematically optimized conditions. Optimization of the chelator-to-antibody ratio, pH, temperature, and incubation time was performed to maximize the radiochemical yield while preserving antibody immunoreactivity and structural integrity. The radioconjugate was purified and characterized using instant thin-layer chromatography and size-exclusion high-performance liquid chromatography. In vitro stability was assessed in phosphate-buffered saline and human serum, while cellular binding and internalization studies were conducted using GPC3-expressing HepG2 cells. In vivo biodistribution, pharmacokinetics, and therapeutic efficacy were evaluated in the tumor-bearing mice. Results: The developed radioconjugate demonstrated high radiolabeling efficiency (96.8% ± 1.2%) and radiochemical purity (>98%) with excellent stability (>95% up to 72 h). Batch-to-batch reproducibility showed minimal variability across independent preparations. Strong receptor-specific cellular binding (∼82%) and significant internalization were observed, confirming preservation of the biological activity following radiolabeling. Biodistribution studies demonstrated high tumor uptake (18.6% ± 2.1%ID/g at 48 h) with favorable tumor-to-background ratios. Therapeutic evaluation revealed up to 66.4% tumor growth inhibition and significantly prolonged survival without observable systemic toxicity. Conclusions: Findings support the potential of the 177 Lu-DOTA-GPC3 as a promising theranostic radionuclide platform for targeting GPC3-positive HCC and addressing postoperative MRD-associated recurrence.