隐匿性淋巴结扩散和转移性疾病需要对甲状腺癌进行长期影像学和生化评估，甲状腺癌是一种具有弥漫性、小体积疾病倾向的疾病。我们开发了一种 64Cu 标记的血小板衍生生长因子受体 α (PDGFRA) 抗体，用于转移性甲状腺乳头状癌 (PTC) 中 PDGFRA 的免疫 PET。目前的工作描述了小环状 PDGFRA 靶向肽的发现、它们的结合特征，以及用正电子发射体镓 68 (68Ga) 进行放射性标记，用于甲状腺癌模型的体外和体内表征。使用具有两个独立文库和七种不同细胞系的噬菌体展示技术，通过三轮生物淘选以及流式细胞术和重组蛋白的比较分析来选择特定的肽序列。通过使用磷酸化和细胞迁移测定完成表型结合分析。使用荧光标记的 PDGFRA 肽通过热泳和流式细胞术分析体外蛋白质结合。候选肽经过 NOTA 螯合剂修饰，用于 68Ga 放射性标记。在各种甲状腺癌细胞系中研究了体外细胞摄取。 68Ga 标记肽的体内研究包括代谢稳定性和 PET 成像。根据含有和不含 PDGFR α 亚基的生物淘选实验，从原始库（1013 种化合物）中鉴定出了 5 种不同的肽组，从而产生了约 50 种肽。随后的表型筛选揭示了两个核心肽序列（CP16 和 CP18），它们证明了 PDGFRA 磷酸化和细胞迁移水平的显着变化。丙氨酸扫描子文库是根据这两个先导肽序列创建的，并且使用 68Ga-GaCl3 在 pH 4.5 下对肽进行放射性标记，在 34-40 分钟内得到 RCP > 95%，包括 SPE 纯化。环肽 CP18.5 通过视觉干涉颜色测定显示出对细胞迁移、流式细胞术和结合的最强影响。 68Ga 标记的 PDGFRA 靶向肽在甲状腺癌模型中显示出细胞和肿瘤摄取升高，其中 68Ga-NOTA-CP18.5 是主要候选肽。然而，与 68Ga-NOTA-CP18 相比，68Ga-NOTA-CP18.5 的体内代谢稳定性受到损害，但不影响肿瘤摄取或清除情况。第一代放射性标记环肽已被开发为新型放射性示踪剂，特别是 68Ga-NOTA-CP18.5，用于甲状腺癌中 PDGFRA 的分子成像。

Occult nodal spread and metastatic disease require longstanding imaging and biochemical assessments for thyroid cancer, a disease that has a propensity for diffuse, small-volume disease. We have developed a 64Cu-labeled platelet-derived growth factor receptor α (PDGFRA) antibody for immuno-PET of PDGFRA in metastatic papillary thyroid cancer (PTC). The present work describes the discovery of small cyclic PDGFRA-targeting peptides, their binding features, and radiolabeling with positron emitter gallium-68 (68Ga) for in vitro and in vivo characterization in thyroid cancer models. Phage-display technology with two separate libraries and seven different cell lines was used through three rounds of biopanning as well as flow cytometry and comparative analysis with recombinant protein to select specific peptide sequences. Phenotypic binding analysis was completed by using phosphorylation and cell migration assays. In vitro protein binding was analyzed with thermophoresis and flow cytometry using the fluorescent-labeled PDGFRA peptide. Peptide candidates were modified with the NOTA chelator for radiolabeling with 68Ga. In vitro cell uptake was studied in various thyroid cancer cell lines. In vivo studies of 68Ga-labeled peptides included metabolic stability and PET imaging. From the original library (1013 compounds), five different peptide groups were identified based on biopanning experiments with and without the α subunit of PDGFR, leading to ∼50 peptides. Subsequent phenotypic screening revealed two core peptide sequences (CP16 and CP18) that demonstrated significant changes in the level of PDGFRA phosphorylation and cell migration. Alanine scan sublibraries were created from these two lead peptide sequences, and peptides were radiolabeled using 68Ga-GaCl3 at pH 4.5, resulting in RCP > 95% within 34-40 min, including SPE purification. Cyclic peptide CP18.5 showed the strongest effects on cell migration, flow cytometry, and binding by visual interference color assay. 68Ga-labeled PDGFRA-targeting peptides showed elevated cell and tumor uptake in models of thyroid cancer, with 68Ga-NOTA-CP18.5 being the lead candidate. However, metabolic stability in vivo was compromised for 68Ga-NOTA-CP18.5 vs 68Ga-NOTA-CP18 but without impacting tumor uptake or clearance profiles. First-generation radiolabeled cyclic peptides have been developed as novel radiotracers, particularly 68Ga-NOTA-CP18.5, for the molecular imaging of PDGFRA in thyroid cancer.