This study will determine the safety and efficacy of DFP-10917 in patients with AML or ALL. The Phase I dose-escalation portion of the study will determine the highest tolerable dose and regimen (7 or 14 day continuous infusion) based on safety data in patients with refractory or relapsed AML or ALL. The phase II portion will investigate the safety and efficacy of DFP-10917, at the dose and regimen to be determined in the Phase I portion, in patients with refractory or relapsed AML.