A humanized monoclonal antibody directed against the activator of g-proteins signaling (AGS) cell surface protein AGS-16 with potential antineoplastic activity. Anti-AGS-16 monoclonal antibody AGS-16M18 selectively binds to AGS-16, triggering complement-dependent cell lysis (CDCL) and antibody-dependent cell-mediated cytotoxicity (ADCC) in tumor cells expressing AGS-16. While normally expressed at low levels in the proximal tubules of the kidney, AGS-16 has been found to be overexpressed in more than 95% of kidney and 40% of liver neoplasms.