The membrane protein carbonic anhydrase IX (CAIX) is highly expressed in many hypoxic or von Hippel-Lindau tumor suppressor–mutated tumor types. Its restricted expression in healthy tissues makes CAIX an attractive diagnostic and therapeutic target. DPI-4452 is a CAIX-targeting cyclic peptide with a DOTA cage, allowing radionuclide chelation for theranostic purposes. Here, we report CAIX expression in multiple tumor types and provide in vitro and in vivo evaluations of ⁶⁸Ga-labeled DPI-4452 ([⁶⁸Ga]Ga-DPI-4452) and ¹⁷⁷Lu-labeled DPI-4452 ([¹⁷⁷Lu]Lu-DPI-4452). Methods: CAIX expression was assessed by immunohistochemistry with a panel of tumor and healthy tissues. The molecular interactions of complexed and uncomplexed DPI-4452 with CAIX were assessed by surface plasmon resonance and cell-binding assays. In vivo characterization of radiolabeled and nonradiolabeled DPI-4452 was performed in HT-29 colorectal cancer (CRC) and SK-RC-52 clear cell renal cell carcinoma (ccRCC) human xenograft mouse models and in healthy beagle dogs. Results: Overexpression of CAIX was shown in several tumor types, including ccRCC, CRC, and pancreatic ductal adenocarcinoma. DPI-4452 specifically and selectively bound CAIX with subnanomolar affinity. In cell-binding assays, DPI-4452 displayed comparably high affinities for human and canine CAIX but a much lower affinity for murine CAIX, demonstrating that the dog is a relevant species for biodistribution studies. DPI-4452 was rapidly eliminated from the systemic circulation of beagle dogs. The highest uptake of [⁶⁸Ga]Ga-DPI-4452 and [¹⁷⁷Lu]Lu-DPI-4452 was observed in the small intestine and stomach, 2 organs known to express CAIX. Uptake in other organs (e.g., kidneys) was remarkably low. In HT-29 and SK-RC-52 xenograft mouse models, both [⁶⁸Ga]Ga-DPI-4452 and [¹⁷⁷Lu]Lu-DPI-4452 showed tumor-selective uptake; in addition, [¹⁷⁷Lu]Lu-DPI-4452 significantly reduced tumor growth. These results demonstrated the theranostic potential of DPI-4452. Conclusion: DPI-4452 selectively targets CAIX. [⁶⁸Ga]Ga-DPI-4452 and [¹⁷⁷Lu]Lu-DPI-4452 localized to tumors and were well tolerated in mice. [¹⁷⁷Lu]Lu-DPI-4452 demonstrated strong tumor growth inhibition in 2 xenograft mouse models. Thus, the 2 agents potentially provide a theranostic approach for selecting and treating patients with CAIX-expressing tumors such as ccRCC, CRC, and pancreatic ductal adenocarcinoma.

膜蛋白碳酸酐酶 IX (CAIX) 在许多缺氧或 von Hippel-Lindau 抑癌基因突变的肿瘤类型中高度表达。它在健康组织中的有限表达使 CAIX 成为有吸引力的诊断和治疗靶点。 DPI-4452 是一种具有 DOTA 笼的 CAIX 靶向环肽，可与放射性核素螯合以用于治疗诊断目的。在这里，我们报告了多种肿瘤类型中的 CAIX 表达，并提供了⁶⁸ Ga 标记的 DPI-4452 ([ ⁶⁸ Ga]Ga-DPI-4452) 和¹⁷⁷ Lu 标记的 DPI-4452 ([ ¹⁷⁷ Lu])的体外和体内评估。卢-DPI-4452）。方法：通过免疫组织化学对一组肿瘤和健康组织评估 CAIX 表达。通过表面等离子共振和细胞结合测定评估了复合和未复合的 DPI-4452 与 CAIX 的分子相互作用。在 HT-29 结直肠癌 (CRC) 和 SK-RC-52 透明细胞肾细胞癌 (ccRCC) 人异种移植小鼠模型以及健康比格犬中进行了放射性标记和非放射性标记 DPI-4452 的体内表征。结果： CAIX 在多种肿瘤类型中过度表达，包括 ccRCC、CRC 和胰腺导管腺癌。 DPI-4452 以亚纳摩尔亲和力特异性、选择性地结合 CAIX。在细胞结合测定中，DPI-4452 对人和犬 CAIX 显示出较高的亲和力，但对鼠 CAIX 的亲和力要低得多，这表明狗是生物分布研究的相关物种。 DPI-4452 迅速从比格犬的体循环中消除。 [ ⁶⁸ Ga]Ga-DPI-4452 和[ ¹⁷⁷ Lu]Lu-DPI-4452的最高摄取在小肠和胃（已知表达 CAIX 的 2 个器官）中观察到。其他器官（例如肾脏）的摄取量非常低。在HT-29和SK-RC-52异种移植小鼠模型中，[ ⁶⁸ Ga]Ga-DPI-4452和[ ¹⁷⁷ Lu]Lu-DPI-4452均表现出肿瘤选择性摄取；此外，[ ¹⁷⁷ Lu]Lu-DPI-4452 显着减少肿瘤生长。这些结果证明了 DPI-4452 的治疗诊断潜力。结论： DPI-4452 选择性靶向 CAIX。 [ ⁶⁸ Ga]Ga-DPI-4452 和[ ¹⁷⁷ Lu]Lu-DPI-4452 定位于肿瘤并且在小鼠中具有良好的耐受性。 [ ¹⁷⁷ Lu]Lu-DPI-4452 在 2 个异种移植小鼠模型中表现出强大的肿瘤生长抑制作用。因此，这两种药物可能为选择和治疗患有表达 CAIX 的肿瘤（例如 ccRCC、CRC 和胰腺导管腺癌）的患者提供治疗诊断方法。