Study to Evaluate the Safety and Tolerability of EP0042

This study tests an experimental oral drug called EP0042 in people with difficult-to-treat blood cancers, including acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and chronic myelomonocytic leukemia (CMML), whose cancer has returned or stopped responding to prior treatments. **You may be eligible if...** - You are 18 years old or older - You have been diagnosed with AML, MDS, or CMML confirmed by pathology - Your cancer has returned (relapsed) or stopped responding (refractory) to prior treatments, and you have exhausted or are ineligible for other available therapies - You are in reasonable general health (ECOG performance status 0–2) - You are able to swallow pills - You have had your cancer's mutation status tested **You may NOT be eligible if...** - Your disease is well-controlled or in complete remission - You have serious uncontrolled medical conditions - You are unable to complete at least one 28-day treatment cycle - You are pregnant or breastfeeding - You have severe liver or kidney problems Talk to your doctor to see if this trial is right for you.