This trial studies the side effects of enasidenib and to see how well it works in treating patients with acute myeloid leukemia that has come back after treatment (relapsed) or has been difficult to treat with chemotherapy (refractory). Patients must also have a specific genetic change, also called a mutation, in a protein called IDH2. Enasidenib may stop the growth of cancer cells by blocking the mutated IDH2 protein, which is needed for cell growth.