[Lu]Lu-labeled anti-claudin-18.2 antibody demonstrated radioimmunotherapy potential in gastric cancer mouse xenograft models.

Purpose: Gastric cancer (GC), one of the most prevalent and deadliest tumors worldwide, is often diagnosed at an advanced stage with limited treatment options and poor prognosis. The development of a CLDN18.2-targeted radioimmunotherapy probe is a potential treatment option for GC.

Methods: The CLDN18.2 antibody TST001 (provided by Transcenta) was conjugated with DOTA and radiolabeled with the radioactive nuclide Lu. The specificity and targeting ability were evaluated by cell uptake, imaging and biodistribution experiments. In BGC823/AGS mouse models, the efficacy of [Lu]Lu-TST001 against CLDN18.2-expressing tumors was demonstrated, and toxicity was evaluated by H&E staining and blood sample testing.

Results: [Lu]Lu-TST001 was labeled with an 99.17%±0.32 radiochemical purity, an 18.50 ± 1.27 MBq/nmol specific activity and a stability of ≥ 94% after 7 days. It exhibited specific and high tumor uptake in CLDN18.2-positive xenografts of GC mouse models. Survival studies in BGC823 and AGS tumor-bearing mouse models indicated that a low dose of 5.55 MBq and a high dose of 11.10 MBq [Lu]Lu-TST001 significantly inhibited tumor growth compared to the saline control group, with the 11.1 MBq group showing better therapeutic efficacy. Histological staining with hematoxylin and eosin (H&E) and Ki67 immunohistochemistry of residual tissues confirmed tumor tissue destruction and reduced tumor cell proliferation following treatment. H&E showed that there was no significant short-term toxicity observed in the heart, spleen, stomach or other important organs when treated with a high dose of [Lu]Lu-TST001, and no apparent hematotoxicity or liver toxicity was observed.

Conclusion: In preclinical studies, [Lu]Lu-TST001 demonstrated significant antitumor efficacy with acceptable toxicity. It exhibits strong potential for clinical translation, providing a new promising treatment option for CLDN18.2-overexpressing tumors, including GC.