This study is for patients that have been diagnosed with a type of cancer called Acute Myeloid Leukemia (AML). The investigational drug in this study is ONO-7475. The purpose of this study is to see whether ONO-7475 slows down the growth of cells that cause cancers like leukemias such as AML. The estimated duration of study participation in Part A is 6 months. You can continue in the study as long as you are gaining benefit from the study treatment.