A recombinant humanized monoclonal antibody directed against the tumor-associated antigen (TAA) Claudin18.2 (CLDN18.2; A2 isoform of claudin-18), with potential immunostimulating and antineoplastic activities. Upon administration, anti-claudin18.2 monoclonal antibody AB011 specifically targets, binds to and inhibits CLDN18.2 expressed on tumor cells. This may kill CLDN18.2-expressing tumor cells and inhibit cell proliferation. CLDN18.2, a tight junction protein and stomach-specific isoform of claudin-18, is expressed on a variety of tumor cells, but its expression in healthy tissues is strictly confined to short-lived differentiated epithelial cells of the gastric mucosa.