Daunorubicin is an inhibitor of DNA topoisomerase II . Daunorubicin is an anthracycline antibiotic. It is also used as an effective chemotherapeutic agent against tumors especially acute myeloid leukaemia and acute lymphocytic leukaemia. Daunorubicin can affect the metabolism and synthesis of DNA and RNA. In the in vitro assay, daunorubicin inhibits the incorporation of thymidine and uridine into L1210 cells. It also inhibits the incorporation of labeled precursors into the isolated DNA and RNA from incubated cells. When treated with leukemic cells isolated from acute lymphocytic leukemia patients, daunorubicin significantly inhibits the biosynthesis of the DNA and RNA macromolecules .