Leflunomide in Combination With Decitabine for Treatment of Relapsed or Refractory Myelodysplastic Syndromes

Inclusion Criteria: * Patient has pathologically confirmed diagnosis of MDS * Patient has currently measurable disease meeting the following criteria: * Bone marrow biopsy with more than 5% blasts, AND * Absolute neutrophil count (ANC) less than 1,000/mcL, and/or platelet count less than 100,000/mcL and/or hemoglobin levels less than 10g/dL * Patient has received one prior treatment with a DNA methyltransferase inhibitor (DNMTi), also commonly called hypomethylating agent (HMA). Patients whose MDS has IDH1/IDH2 mutations should have received at least one available IDH1/IDH2 inhibitor * Patient has an Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to 2 * Patient has the following required baseline laboratory data (eligibility can be based on local lab results): * Total serum bilirubin level less than or equal to 2 times ULN * Estimated glomerular filtration rate (eGFR) greater than or equal to 45 mL/min/1.73 m2 * Patients who have undergone alloHSCT are eligible if they are more than 28 days post stem cell infusion, have no evidence of GVHD \> Grade 1, and are more than a week off all immunosuppressive therapy * If a female of childbearing potential, the patient has a negative serum or urine pregnancy test result within 7 days prior to the first dose of treatment. Women of non-childbearing potential are those who are postmenopausal greater than one year or who have had a bilateral tubal ligation or hysterectomy * If female of childbearing potential or a male patient, patient agrees to use an effective contraceptive method from the time of informed consent, during the course of the study, and for 3 months following the last dose of treatment * Patient understands and voluntarily signs the written informed consent prior to any study-specific procedures. A copy of the signed informed consent form will be retained by the treating institution Exclusion Criteria: * Patients receiving any other investigational agents, or concurrent chemotherapy or immunotherapy * Patients with progression to acute myeloid leukemia * Patients with other malignancies requiring systemic chemotherapy, immunotherapy or targeted therapy in the last four weeks * Patients with uncontrolled bacterial, viral or fungal infections (undergoing appropriate treatment and with progression of clinical symptoms) * Patients with active or latent tuberculosis * Uncontrolled intercurrent illness including, but not limited to, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that per Principal Investigator's judgment would limit compliance with study requirements * Females who are pregnant or breast feeding * Any other clinical conditions that in the opinion of the investigator would make the subject unsuitable for the study