Claudin18.2 (CLDN18.2), a member of tight junction protein family, is strictly limited to differentiated epithelial cells of gastric mucosa and multiple tumor types, such as gastric, esophageal and pancreatic cancers. We have generated a novel species cross-reactive CLDN18.2 specific antibody, and labeled it with “Next Generation” radionuclide I-124 (124I-18B10).
I-124 was produced by the medical cyclotron using 124Te (p, n) 124I reaction. In the cell-based assay, the uptake of 124I-18B10 in MKN45-CLDN18.2 (CLDN18.2+ cell line) and MKN45 (CLDN18.2- cell line) were detected at 10, 30, 60 and 120 min, and the blocking group using cold 18B10 antibody to block uptake was also evaluated. PDX-bearing mice, which were selected by immunohistochemical (IHC) method and assessed as CLDN18.2+ or CLDN18.2-, were injected with either 18.5 MBq 18F- fluorodeoxyglucose (18F-FDG), or 124I-18B10, or 124I-hIgG via the tail vein, and Micro-PET/CT images were taken at 2, 60 and 120h post injection.
The specific activity of 124I-18B10 was 0.62 mCi/mg antibody and the labeling rate was higher than 95%. The cell-based assay showed that specific uptake of it by the MKN45-CLDN18.2 cells was significantly higher than that of by the MKN45 cells (23.51±0.47 % vs 8.69±0.35 % at 2 h, P<0.05). Both uptake assay and competitive binding assay in the MKN45-CLDN18.2 cells showed that cold 18B10 antibody could significantly reduce the uptake and binding of 124I-18B10 (15.33±0.82 % at 2 h, P<0.05). As expected, the uptake of 124I-hIgG was low (5.21±0.29 % at 2 h). In PDX bearing mice, the uptake of 18F-FDG in tumor sites was low. The distribution of 124I-18B10 in CLDN18.2+ PDX bearing mice was increasingly enriched in the tumor sites over time. The uptake signals of 124I-18B10 in CLDN18.2- PDX bearing mice in all tissues and tumors remained similar at different time points.
The 124I-18B10 antibody has good radio-chemical characteristics and stability. The cell uptake assay and competitive binding assay demonstrated that the probe is highly specific to CLDN18.2. Micro-PET images of PDX bearing mice demonstrated that 124I-18B10 was enriched in the lesion of CLDN18.2 positive tumors rather than negative tumors or normal tissues.
Peking University Cancer Hospital & Institute.
Has not received any funding.
F. Teng, Y. Gu, X. Qian: Full/Part-time employment: Research, Mabspace Biosciences (Suzhou) Co. Ltd., Suzhou, China. All other authors have declared no conflicts of interest.