IBI343 is an anti-CLDN18.2 ADC; it binds CLDN18.2, internalizes, and releases a topoisomerase I inhibitor payload that causes DNA damage and apoptosis (±ADCC/CDC). Topoisomerase I is the intracellular payload target, not the antigen recognized by the drug, so cells expressing only topoisomerase I are not specifically targeted or directly killed.