Hepatocellular carcinoma (HCC) is a significant cause of morbidity and mortality worldwide, with limited therapeutic options for advanced disease. Targeted α-therapy is an emerging class of targeted cancer therapy in which α-particle–emitting radionuclides, such as ²²⁷Th, are delivered specifically to cancer tissue. Glypican-3 (GPC3) is a cell surface glycoprotein highly expressed on HCC. In this study, we describe the development and in vivo efficacy of a ²²⁷Th-labeled GPC3-targeting antibody conjugate (²²⁷Th-octapa-αGPC3) for treatment of HCC in an orthotopic murine model. Methods: The chelator p-SCN-Bn-H₄octapa-NCS (octapa) was conjugated to a GPC3-targeting antibody (αGPC3) for subsequent ²²⁷Th radiolabeling (octapa-αGPC3). Conditions were varied to optimize radiolabeling of ²²⁷Th. In vitro stability was evaluated by measuring the percentage of protein-bound ²²⁷Th by -ray spectroscopy. An orthotopic athymic Nu/J murine model using HepG2-Red-FLuc cells was developed. Biodistribution and blood clearance of ²²⁷Th-octapa-αGPC3 were evaluated in tumor-bearing mice. The efficacy of ²²⁷Th-octapa-αGPC3 was assessed in tumor-bearing animals with serial measurement of serum α-fetoprotein at 23 d after injection. Results: Octapa-conjugated αGPC3 provided up to 70% ²²⁷Th labeling yield in 2 h at room temperature. In the presence of ascorbate, at least 97.8% of ²²⁷Th was bound to αGPC3-octapa after 14 d in phosphate-buffered saline. In HepG2-Red-FLuc tumor-bearing mice, highly specific GPC3 targeting was observed, with significant ²²⁷Th-octapa-αGPC3 accumulation in the tumor over time and minimal accumulation in normal tissue. Twenty-three days after treatment, a significant reduction in tumor burden was observed in mice receiving a 500 kBq/kg dose of ²²⁷Th-octapa-αGPC3 by tail-vein injection. No acute off-target toxicity was observed, and no animals died before termination of the study. Conclusion: ²²⁷Th-octapa-αGPC3 was observed to be stable in vitro; maintain high specificity for GPC3, with favorable biodistribution in vivo; and result in significant antitumor activity without significant acute off-target toxicity in an orthotopic murine model of HCC.

肝细胞癌 (HCC) 是全世界发病率和死亡率的重要原因，晚期疾病的治疗选择有限。靶向 α 疗法是一类新兴的靶向癌症疗法，其中发射 α 粒子的放射性核素（例如²²⁷ Th）专门递送至癌组织。Glypican-3 (GPC3) 是一种在 HCC 上高度表达的细胞表面糖蛋白。^{在这项研究中，我们描述了227} Th 标记的 GPC3 靶向抗体偶联物 ( ²²⁷ Th-octapa-αGPC3) 在原位小鼠模型中治疗 HCC的开发和体内疗效。方法：螯合剂p -SCN-Bn-H ₄octapa-NCS (octapa) 与 GPC3 靶向抗体 (αGPC3) 偶联，用于随后的²²⁷ Th 放射性标记 (octapa-αGPC3)。改变条件以优化²²⁷ Th 的放射性标记。体外稳定性通过射线光谱测量蛋白质结合的^{227 Th 的百分比来评价。}开发了使用 HepG2-Red-FLuc 细胞的原位无胸腺 Nu/J 鼠模型。在荷瘤小鼠中评估了²²⁷ Th-octapa-αGPC3 的生物分布和血液清除率。通过在注射后 23 天连续测量血清甲胎蛋白，评估了²²⁷ Th-octapa-αGPC3 在荷瘤动物中的功效。结果： Octapa 缀合的 αGPC3 提供高达 70% ²²⁷室温下 2 小时内的标记产量。在存在抗坏血酸的情况下，在磷酸盐缓冲盐水中 14 天后，至少 97.8% 的²²⁷ Th 与 αGPC3-octapa 结合。在 HepG2-Red-FLuc 荷瘤小鼠中，观察到高度特异性的 GPC3 靶向，随着时间的推移肿瘤中显着的²²⁷ Th-octapa-αGPC3 积累和正常组织中的最小积累。治疗后 23 天，在通过尾静脉注射接受 500 kBq/kg 剂量的²²⁷ Th-octapa-αGPC3 的小鼠中观察到肿瘤负荷显着降低。没有观察到急性脱靶毒性，也没有动物在研究结束前死亡。结论： ²²⁷观察到 Th-octapa-αGPC3 在体外稳定；保持对 GPC3 的高特异性，具有良好的体内生物分布；并在 HCC 的原位小鼠模型中产生显着的抗肿瘤活性而没有显着的急性脱靶毒性。