Additional Study Information: The purpose of the study is to test the following: 1) The safety and tolerability (how you feel when you take the drug) of the study drug, 2) The pharmacokinetics (PK) (how the study drug is absorbed within your body, spread throughout your body, and eliminated from your body) of the study drug, 3) The pharmacodynamics (PD) (how the study drug affects certain proteins related to your cancer) of the study drug 4) The initial clinical effect (how the study drug affects your cancer) of the study drug, and 5) To determine the most appropriate dose (strength) and how often the drug should be taken. The drug being tested in this study, ASTX295, is investigational. This means it has not been approved for the treatment of cancer in any country. This is the first clinical study of ASTX295 in humans. In this study, all subjects will receive the study drug; there is no placebo treatment. There are 2 Phases in this study, Phase 1 (early stage) and Phase 2 (late-stage).