An antibody-drug conjugate (ADC) composed of a human monoclonal antibody directed against the tumor-associated antigen (TAA) CD19 (cluster of differentiation 19), that is site-specifically conjugated with a tumor-cleavable beta-glucuronide linker to a tumor-cleavable prodrug of pyrrolobenzodiazepine (PBD) dimer, with potential antineoplastic activity. Upon intravenous administration, the monoclonal antibody moiety of anti-CD19 ADC IKS03 targets and binds to CD19 expressed on tumor cells. Upon binding and internalization, both the linker and prodrug are selectively cleaved by lysosomal b-glucuronidase overexpressed in tumor cells. Free PBD is released and forms highly cytotoxic DNA interstrand cross-links, thereby blocking cell division and killing CD19-expressing cancer cells. CD19 antigen is a B-cell specific cell surface antigen overexpressed in B-cell lineage malignancies.