Lintuzumab (also known as SGN-33 or HuM195) is a humanized monoclonal antibody that targets CD33, a cell-surface glycoprotein highly expressed on myeloid cells and on the majority of acute myeloid leukemia (AML) blasts. It was initially developed as a naked antibody aiming to induce antibody-dependent cellular cytotoxicity (ADCC) against AML cells. Later, it was extensively studied in conjugate forms, most notably as a carrier for radioactive isotopes (e.g., actinium-225 or lutetium-177) in targeted alpha-particle therapy (TAT) or radioimmunotherapy. These approaches aimed to deliver highly cytotoxic radiation directly to CD33+ leukemia cells while sparing healthy tissues. Despite extensive clinical investigation, lintuzumab has not achieved regulatory approval as a standalone therapy.