Testing the Addition of an IDH2 Inhibitor, Enasidenib, to Usual Treatment (Cedazuridine-Decitabine) for Higher-Risk Myelodysplastic Syndrome (MDS) With IDH2 Mutation (A MyeloMATCH Treatment Trial)

Inclusion Criteria: * GENERAL MYLEOMATCH REGISTRATION CRITERIA: * Patients must be registered to the Master Screening and Reassessment Protocol (MYELOMATCH) and assigned to this protocol by the MATCHBox Treatment Verification Team. * Participants must not have received prior anti-cancer therapy for AML or MDS. * Note: Hydroxyurea to control the white blood cell count (WBC) is allowed. * Note: Prior erythroid stimulating agent (ESA) is not considered prior therapy for the purposes of eligibility. * Participants must not be currently receiving any cytarabine-containing therapy other than up to 1 g/m\^2 of cytarabine, which is allowed for urgent cytoreduction. The use of prior hydroxyurea, all-trans retinoic acid (ATRA), BCR-ABL directed tyrosine kinase inhibitor, erythropoiesis-stimulating agent, thrombopoietin receptor agonist and lenalidomide is allowed * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Patients must have a morphologically-confirmed diagnosis of MDS with a Revised International Prognostic Scoring System (IPSS-R) score ≥ 4. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Patients must have a detectable pathogenic IDH2 mutation based on the National Cancer Institute (NCI) Myeloid Panel. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): No prior treatment with deoxyribonucleic acid (DNA) methyltransferase inhibitors (ASTX727, azacitidine, or decitabine). * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Prior treatment with growth factors (ESA, granulocyte colony-stimulating factor \[g-CSF\], thrombopoietin \[TPO\] agonist) or luspatercept is allowed. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Prior treatment with lenalidomide with a maximum limit of 1 month of exposure is allowed. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Patients with therapy-related MDS are allowed. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Age ≥ 18 years. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Total bilirubin ≤ 1.5 x upper limit of normal (ULN) * Unless elevated due to Gilbert's syndrome. In patients with Gilbert's syndrome, if the total bilirubin is ≤ 3.0 x ULN, then they are eligible for enrollment. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase \[SGOT\])/alanine aminotransferase (ALT) (serum glutamic-pyruvic transaminase \[SGPT\]) ≤ 3.0 x upper limit of normal (ULN). * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Creatinine clearance ≥ 30 mL/min * To be calculated using Cockroft Gault formula. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Not pregnant and not nursing, because this study involves: an agent that has known genotoxic, mutagenic and teratogenic effects. * Therefore, for women of childbearing potential only, a negative pregnancy test done as part of screening lab work prior to registration is required. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): HIV-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months prior to registration are eligible for this trial. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated. * REGISTRATION ELIGIBILITY CRITERIA (STEP 1): Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load. * RE-REGISTRATION ELIGIBILITY CRITERIA (STEP 2): Patients on the ASTX727 monotherapy arm (Regimen 1) that do not achieve a CR (complete response), CRL (CR with limited count recovery), or CRh (CR with partial count recovery) after completing 6 cycles of study treatment. * RE-REGISTRATION ELIGIBILITY CRITERIA (STEP 2): ECOG performance status ≤ 2. * RE-REGISTRATION ELIGIBILITY CRITERIA (STEP 2): Total bilirubin ≤ 1.5 x upper limit of normal (ULN). * Unless elevated due to Gilbert's syndrome. In patients with Gilbert's syndrome if the total bilirubin is ≤ 3.0 x ULN, then they are eligible for enrollment. * RE-REGISTRATION ELIGIBILITY CRITERIA (STEP 2): AST (SGOT)/ALT (SGPT) ≤ 3.0 x upper limit of normal (ULN) * RE-REGISTRATION ELIGIBILITY CRITERIA (STEP 2): Creatinine clearance ≥ 30 mL/min * To be calculated using Cockroft Gault formula. * RE-REGISTRATION ELIGIBILITY CRITERIA (STEP 2): Not pregnant and not nursing, because this study involves: an agent that has known genotoxic, mutagenic and teratogenic effects.