An antibody-drug conjugate (ADC) composed of an immunoglobulin G1 (IgG1) monoclonal antibody directed against the tumor-associated antigen (TAA) Claudin 18.2 (CLDN18.2; A2 isoform of claudin-18) conjugated, via a cleavable linker, to a topoisomerase 1 inhibitor, with potential antineoplastic activity. Upon administration of anti-CLDN18.2 ADC SHR-A1904, the anti-CLDN18.2 monoclonal antibody moiety specifically targets and binds to CLDN18.2 expressed on tumor cells. Upon binding, internalization and linker cleavage, the topoisomerase 1 inhibitor is released and inhibits DNA topoisomerase I activity, thereby inhibiting DNA replication and resulting in cell cycle arrest and apoptosis in tumor cells expressing CLDN18.2. CLDN18.2, a tight junction protein and stomach-specific isoform of claudin-18, is expressed on a variety of tumor cells. Its expression in healthy tissues is strictly confined to short-lived differentiated epithelial cells of the gastric mucosa.