He Yingfang, Tian Ruhua, Xu Dong, Wu Yanfei, Rina Sa, Chen Tengxiang, Guan Yihui, Xie Tianwu, Ying Tianlei, Xie Fang, Han Junbin
Institute of Radiation Medicine, Fudan University, Xietu Road 2094, Shanghai, 200032, China.
Department of Physiology, School of Basic Medicine, Guizhou Medical University, Guiyang, China.
Eur J Nucl Med Mol Imaging. 2025 Jan;52(2):611-622. doi: 10.1007/s00259-024-06941-1. Epub 2024 Oct 8.
Trophoblast glycoprotein, the so-called 5T4, is an oncofetal antigen expressed in many different cancers. However, no 5T4-specific radioligand is employed in the clinic for non-invasive diagnosis. Thus, the aim of the current study was to develop a PET radiotracer for imaging 5T4 expression in preclinical and clinical stages.
A VHH library was constructed by camel immunization. The specificity of the VHHs toward 5T4 antigen was screened through phage display biopanning and periplasmic extract enzyme-linked immunosorbent assay. 1,4,7-Triazacyclononane-1,4,7-triacetate acid (NOTA) derivative was conjugated to the selected VHH. After radiolabeling, microPET/CT and ex vivo biodistribution were conducted using BxPC-3 and MDA-MB-468 tumor-bearing mice. Cold VHH was co-injected with the tracer to challenge its binding in vivo. For the pilot clinical study, PET/CT images were acquired at 1 h after injection of tracer in patients with pathologically confirmed primary and metastatic tumors.
A library with a capacity of 1.2 × 10 colony-forming units was constructed after successful camel immunization. Nb1-40 with a median effect concentration of 0.43 nM was selected. After humanization, the resulting H006 maintained a high affinity towards 5T4. [Ga]Ga-NOTA-H006 with the molar activities of 6.48-54.2 GBq/µmol was prepared with high radiochemical purity (> 98%). Using [Ga]Ga-NOTA-H006, microPET/CT revealed a clear visualization of 5T4 expression in BxPC-3 tumor-bearing mice. Ex vivo biodistribution showed that the highest tumor-to-blood ratio (∼ 3-fold) and tumor-to-muscle ratio (∼ 5-fold) were achieved at 60 min post-injection. Co-injection of the cold H006 at a dose of 1.5 mg/kg significantly reduced the tumor uptake (p < 0.0001). In the pilot clinical study, [Ga]Ga-NOTA-H006 demonstrated its capacity to map 5T4-positive lesions in humans and yielded a mean effective dose of 3.4 × 10 mSv/MBq.
[Ga]Ga-NOTA-H006, which can visualize 5T4 expression in vivo, has been successfully developed. This opens up opportunities for non-invasively studying 5T4 expression through nuclear medicine. Further clinical investigations are warranted to explore its clinical value in disease progression and companion diagnosis.
滋养层糖蛋白，即所谓的5T4，是一种在多种不同癌症中表达的癌胚抗原。然而，临床上尚未使用5T4特异性放射性配体进行非侵入性诊断。因此，本研究的目的是开发一种用于在临床前和临床阶段成像5T4表达的正电子发射断层显像（PET）放射性示踪剂。
通过骆驼免疫构建了一个单域重链抗体（VHH）文库。通过噬菌体展示生物淘选和周质提取物酶联免疫吸附测定筛选VHH对5T4抗原的特异性。将1,4,7-三氮杂环壬烷-1,4,7-三乙酸（NOTA）衍生物与所选的VHH偶联。放射性标记后，使用携带BxPC-3和MDA-MB-468肿瘤的小鼠进行微型PET/CT和离体生物分布研究。将冷的VHH与示踪剂共同注射以挑战其在体内的结合。在初步临床研究中，在注射示踪剂1小时后，对经病理证实的原发性和转移性肿瘤患者进行PET/CT成像。
成功进行骆驼免疫后构建了一个容量为1.2×10菌落形成单位的文库。选择了中位效应浓度为0.43 nM的Nb1-40。人源化后，所得的H006对5T4保持高亲和力。制备了摩尔活度为6.48 - 54.2 GBq/µmol且放射化学纯度高（>98%）的[镓]Ga-NOTA-H006。使用[镓]Ga-NOTA-H006，微型PET/CT清晰显示了携带BxPC-3肿瘤的小鼠中5T4的表达。离体生物分布显示，注射后60分钟时肿瘤与血液的比率最高（约3倍），肿瘤与肌肉的比率最高（约5倍）。以1.5 mg/kg的剂量共同注射冷的H006可显著降低肿瘤摄取（p < 0.0001）。在初步临床研究中，[镓]Ga-NOTA-H006证明了其在人体中描绘5T4阳性病变的能力，平均有效剂量为3.4×10 mSv/MBq。
已成功开发出能够在体内可视化5T4表达的[镓]Ga-NOTA-H006。这为通过核医学非侵入性研究5T4表达开辟了机会。有必要进行进一步的临床研究以探索其在疾病进展和伴随诊断中的临床价值。
