This study is testing a new drug called MRX-2843 for people with certain types of blood cancer that have come back or don't respond to treatment, like acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), or mixed phenotype acute leukemia (MPAL). MRX-2843 is taken by mouth in 28-day cycles. The study is in Phase I, which means it's looking at how safe the drug is and how it behaves in the body. Up to 50 patients, including teens and adults, will join. Some patients will continue to get the drug at a set dose to learn more about its effects.

• The study lasts for multiple 28-day cycles, and patients will be closely monitored during this time.
• Participants must be at least 12 years old, weigh at least 40 kg, and have specific medical conditions.
• Women and men able to have children must use two forms of birth control during the study and for 4 months after.

If you think you might be a fit for this study, it's important to talk with your doctor to understand the risks and benefits before deciding to participate.