ABSTRACT
Claudin18.2(CLDN18.2)is a tight junction protein that is overexpressed in a variety of solid tumors such as gastrointestinal cancer and oesophageal cancer.It has been identified as a promising target and a potential biomarker to diagnose tumor,evaluate efficacy,and determine patient prognosis.TST001 is a recombinant humanized CLDN18.2 antibody that selectively binds to the extracellular loop of human Claudin18.2.In this study,we constructed a solid target radionuclide zirconium-89(89Zr)labled-TST001 to detect the expression of in the human stomach cancer BGC823CLDN18.2 cell lines.The[89Zr]Zr-des-ferrioxamine(DFO)-TST001 showed high radiochemical purity(RCP,＞99％)and specific activity(24.15±1.34 GBq/μmol),and was stable in 5％human serum albumin,and phosphate buffer saline(＞85％RCP at 96 h).The EC50 values of TST001 and DFO-TST001 were as high as 0.413±0.055 and 0.361±0.058 nM(P＞0.05),respectively.The radiotracer had a significantly higher average standard uptake values in CLDN18.2-positive tumors than in CLDN18.2-negative tumors(1.11±0.02 vs.0.49±0.03,P=0.0016)2 days post injection(p.i.).BGC823CLDN18.2 mice models showed high tumor/muscle ratios 96 h p.i.with[89Zr]Zr-DFO-TST001 was much higher than those of the other imaging groups.Immunohistochemistry results showed that BGC823CLDN18.2 tumors were highly positive(+++)for CLDN18.2,while those in the BGC823 group did not express CLDN18.2(-).The results of ex vivo biodistribution studies showed that there was a higher distribution in the BGC823CLDN18.2 tumor bearing mice(2.05±0.16％ID/g)than BGC823 mice(0.69±0.02％ID/g)and blocking group(0.72±0.02％ID/g).A dosimetry estimation study showed that the effective dose of[89Zr]Zr-DFO-TST001 was 0.0705 mSv/MBq,which is within the range of acceptable doses for nuclear medicine research.Taken together,these re-sults suggest that Good Manufacturing Practices produced by this immuno-positron emission tomog-raphy probe can detect CLDN18.2-overexpressing tumors.