RecruitingDrug trialONC201 in Treating Patients With Relapsed or Refractory Acute Leukemia or High-Risk Myelodysplastic SyndromeThis phase I/II trial studies the side effects and best dose of ONC201 and to see how well it works in treating patients with acute leukemia or high-risk myelodysplastic syndrome that has returned after a period of improvement (relapsed) or does not respond to treatment (refractory). ONC201 may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth.