Meng Zheng, Haoqun Ma, Tao Xu, Huiwen Mu, Qingfeng Liu, Kaijie Zhang, Yicong Bian, Hua Zhang, Wei Li, Bin Zhang, Yuanyuan Shan, Xuanhui Peng, Songbing Qin, Yan Wang, Liyan Miao
We aimed to develop and identify a single-domain antibody–based molecular probe to minimize nonspecific renal accumulation while maintaining high tumor affinity and effective uptake. <b>Methods:</b> A CLDN18.2-targeted nanobody, SNA014, was radiolabeled with <sup>68</sup>Ga to yield [<sup>68</sup>Ga]Ga-SNA014.
High renal uptake limits the clinical translation of Claudin 18.2 (CLDN18.2) nanobody probes. We aimed to develop and identify a single-domain antibody–based molecular probe to minimize nonspecific renal accumulation while maintaining high tumor affinity and effective uptake. Methods: A CLDN18.2-targeted nanobody, SNA014, was radiolabeled with 68Ga to yield [68Ga]Ga-SNA014. The binding capability of [68Ga]Ga-SNA014 was evaluated in vitro using flow cytometry, immunohistochemistry, and cell-binding assays. The biologic behavior of [68Ga]Ga-SNA014 in vivo was assessed through small-animal PET imaging, biodistribution studies, and blood pharmacokinetic analysis in human gastric adenocarcinoma xenograft models (both wild-type and CLDN18.2-overexpressing). Furthermore, a preliminary clinical evaluation of [68Ga]Ga-SNA014 was conducted in 3 patients with gastric cancer, including whole-body PET/CT imaging and radiation dosimetry analysis. Results: [68Ga]Ga-SNA014 was successfully synthesized with high radiochemical purity (>95%) and excellent stability both in vitro and in vivo. The probe demonstrated strong binding affinity and specificity toward AGSCLDN18.2 cells. Small-animal PET/CT images of AGSCLDN18.2 tumor–bearing mice exhibited high tumor and stomach uptake and low kidney uptake, and pretreatment with succinylated gelatin further reduced kidney retention. Blood clearance revealed a rapid elimination profile, with a half-life of 47.68 ± 1.83 min. In human PET/CT studies, distinct visualization of lesions was achieved up to 0.5 h postinjection. Dosimetry analysis revealed that the effective radiation dose of [68Ga]Ga-SNA014 was lower than that of standard [18F]FDG PET/CT. Conclusion: These findings demonstrated that [68Ga]Ga-SNA014 exhibits high affinity and specificity and excellent targeting performance and safety, enabling precise detection of CLDN18.2-overexpressing tumors.