A humanized monoclonal antibody recognizing the tumor-specific epitope of mucin-1 (TA-MUC1), with potential antineoplastic activity. Gatipotuzumab targets and binds to the TA-MUC1 epitopes expressed on the cell surface of tumor cells, thereby potentially activating the immune system to induce an antibody-dependent cellular cytotoxicity (ADCC) against the TA-MUC1-expressing tumor cells. TA-MUC1 is designated to MUC1 epitopes with O-glycosylated carbohydrate-induced conformational structures that are tumor-specific, thereby enabling gatipotuzumab to differentiate between tumor MUC1 and non-tumor MUC1 epitopes.