Fu Wenhui, Parent Ephraim E, Gleba Justyna J, Knight Joshua A, Muzik Otto, Copland John A, Cai Hancheng
Department of Radiology, Mayo Clinic, Jacksonville, Florida 32224, United States.
Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida 32224, United States.
Mol Pharm. 2025 Jul 7;22(7):4056-4067. doi: 10.1021/acs.molpharmaceut.5c00325. Epub 2025 May 22.
Advanced thyroid cancers are aggressive and often refractory to the current standard of care. The thyroid-stimulating hormone receptor (TSHR) is highly expressed in thyroid cancers and rarely expressed outside the thyroid, making it a viable target for developing radiotheranostics for imaging and therapy of advanced thyroid cancer. This study reports the radiosynthesis and preclinical evaluation of a Cu-labeled human antibody for positron emission tomography (PET) imaging of TSHR expression in advanced thyroid cancer mouse models. Human anti-TSHR recombinant antibody K1-70 (TSHR-Ab) was labeled with copper-64, yielding [Cu]Cu-NOTA-TSHR-Ab with a radiochemical yield of 46.89 ± 3.74%, radiochemical purity of 98.77 ± 0.89%, and specific activity >212 GBq/μmol ( = 5). studies on TSHR-positive (THJ529T) and wild-type (THJ529T) cells demonstrated the radiotracer's high specificity and nanomolar binding affinity for THJ529T cells, with a dissociation constant () of 4.74 nM and an inhibition constant () of 0.92 nM. ImmunoPET imaging in mice bearing dual-flank tumors (THJ529T and THJ529T) at multiple time points (1, 2, 4, 18, 24, and 48 h) postinjection (p.i.) revealed rapid tumor targeting and high uptake in TSHR-positive thyroid tumors (SUV: 3.63 ± 0.42, 3.82 ± 0.44, and 4.09 ± 0.56 at 18, 24, and 48 h p.i., respectively). Co-injection studies with varying doses of unlabeled TSHR-Ab (0, 25, 50, 100 μg) demonstrated that the coinjection significantly reduced background signals, especially in the spleen, liver, and bone, with a dose of 25 μg effectively reducing off-target signals without affecting tumor uptake. Biodistribution and immunohistochemistry analyses supported these immunoPET imaging results. Furthermore, a comparison study with traditional [F]FDG PET imaging showed that [Cu]Cu-NOTA-TSHR outperformed [F]FDG in tumor detection. In conclusion, [Cu]Cu-NOTA-TSHR-Ab is a promising radiotracer for PET imaging of TSHR-positive advanced thyroid cancers, with the potential to guide and monitor TSHR-targeted therapies. Further clinical evaluation of [Cu]Cu-NOTA-TSHR-Ab could provide valuable insights for patient stratification and optimization of anti-TSHR treatments.
晚期甲状腺癌具有侵袭性，通常对当前的标准治疗方法难治。促甲状腺激素受体（TSHR）在甲状腺癌中高表达，在甲状腺外很少表达，这使其成为开发用于晚期甲状腺癌成像和治疗的放射诊疗药物的可行靶点。本研究报告了一种用于晚期甲状腺癌小鼠模型中TSHR表达正电子发射断层扫描（PET）成像的铜标记人抗体的放射性合成及临床前评估。人抗TSHR重组抗体K1-70（TSHR-Ab）用铜-64标记，得到[⁶⁴Cu]Cu-NOTA-TSHR-Ab，放射化学产率为46.89±3.74%，放射化学纯度为98.77±0.89%，比活度>212 GBq/μmol（n = 5）。对TSHR阳性（THJ529T）和野生型（THJ529T）细胞的研究表明，该放射性示踪剂对THJ529T细胞具有高特异性和纳摩尔级结合亲和力，解离常数（KD）为4.74 nM，抑制常数（KI）为0.92 nM。在双侧肿瘤（THJ529T和THJ529T）小鼠注射后（p.i.）的多个时间点（1、2、4、18、24和48小时）进行的免疫PET成像显示，TSHR阳性甲状腺肿瘤快速靶向且摄取高（分别在注射后18、24和48小时时SUV：3.63±0.42、3.82±0.44和4.09±0.56）。用不同剂量的未标记TSHR-Ab（0、25、50、100μg）进行的共注射研究表明，共注射显著降低了背景信号，尤其是在脾脏、肝脏和骨骼中，25μg的剂量有效降低了非靶向信号而不影响肿瘤摄取。生物分布和免疫组织化学分析支持了这些免疫PET成像结果。此外，与传统的[¹⁸F]FDG PET成像的比较研究表明，[⁶⁴Cu]Cu-NOTA-TSHR在肿瘤检测方面优于[¹⁸F]FDG。总之，[⁶⁴Cu]Cu-NOTA-TSHR-Ab是一种用于TSHR阳性晚期甲状腺癌PET成像的有前景的放射性示踪剂，具有指导和监测TSHR靶向治疗的潜力。对[⁶⁴Cu]Cu-NOTA-TSHR-Ab的进一步临床评估可为患者分层和抗TSHR治疗的优化提供有价值的见解。
