This study of AMG 900 will be conducted in two parts: dose escalation and dose expansion. The dose escalation part of the study is aimed at evaluating the safety, tolerability and PK (pharmacokinetics) of oral AMG 900 in subjects with acute myeloid leukemia. Up to 93 subjects may be enrolled in dose escalation. The dose expansion part of the study will consist of 20 subjects with acute myeloid leukemia. The dose of AMG 900 will be dependent upon data from the dose escalation part of the study.