Safety and Efficacy Study of PRI-724 in Subjects With Advanced Myeloid Malignancies

PRI-724 is a new investigational drug being studied to treat subjects with cancer who have advanced myeloid malignancies. PRI-724 is thought to work by blocking the Wnt signaling pathway that cancer cells need to grow and spread (metastasize). Purpose: * To test the safety of PRI-724 when taken intravenously (through the vein). * To observe whether PRI-724 can slow or stop the progression of leukemia. * To find the Maximum Tolerated Dose (highest safe dose) in the first two parts of the study. * To find the dose of PRI-724 that should be used in the third part of the study and possible future clinical trials that will study effectiveness and additional safety. * To test the safety of combining PRI-724 with an approved cancer drug called dasatinib in treating chronic myeloid leukemia (CML). * To evaluate whether the combination of PRI-724 with the approved cancer drug dasatinib slows or stops the progression of chronic myeloid leukemia (CML). * To test the safety of combining PRI-724 with an approved cancer drug called Cytarabine in treating acute myelogenous leukemia (AML). * To evaluate whether the combination of PRI-724 with the approved cancer drug Cytarabine slows or stops the progression of acute myelogenous leukemia (AML). * To measure how much PRI-724 appears and remains in the blood after infusion. * To measure several signals called biomarkers associated with cancer in the blood to see if PRI-724 affects those signals. Study Design: This will be a single center, open-label escalating-dose cohort study with 3 parts: Part I during which the MTD will be determined in acute group patients; Part II during which the MTD will be determined in non-acute group patients; and Part III during which safety and tolerability of escalating doses of PRI-724 will be assessed in combination with dasatinib for CML patients or low dose ara-C therapy for AML patients ≥ 65 years of age.