The active ingredient in a drug used with other drugs to treat acute lymphoblastic leukemia and acute myeloid leukemia. It is also being studied in the treatment of other types of cancer. Daunorubicin blocks a certain enzyme needed for cell division and DNA repair, and it may kill cancer cells. It is a type of anthracycline antibiotic and a type of topoisomerase inhibitor. Also called daunomycin.