 Acute myeloid leukemia AML is a heterogeneous group of diseases characterized by uncontrolled proliferation of the myeloid line of white blood cells and impaired production of normal blood cells. If untreated, patients die of infection or bleeding usually in a matter of weeks. CSL360 is a neutralising monoclonal antibody which is believed to target the cells that are thought to drive AML but that are not effectively killed by standard treatment. The aims of the study are to determine a biologically active dose of CSL360 and generate understanding of a rational schedule of administration for future studies. 