Inclusion Criteria:

* Diagnosis of MDS by World Health Organization criteria, and either

1. International Prognostic Scoring System (IPSS) low risk or intermediate-1 risk without 5q deletion and failed treatment (no response, loss of response, progressive disease/treatment intolerance) following:

i. 4 cycles hypomethylating agent; or ii. 4 cycles hypomethylating agent, or lenalidomide or erythropoietin stimulating agent (ESA).
2. IPSS low risk or intermediate-1 risk with 5q deletion and failed treatment following:

i. 4 cycles of lenalidomide and hypomethylating agent; or ii. 4 cycles of lenalidomide.
3. IPSS intermediate-2 risk or high risk and failed treatment following 4 cycles hypomethylating agent.
* Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 2
* Screening laboratory values:

1. Renal glomerular filtration rate (GFR) ≥ 30 ml/min;
2. Aspartate aminotransferase (AST) / Alanine aminotransferase (ALT) ≤ 3.0 times upper limit of normal;
3. Bilirubin \< 1.5 times upper limit of normal;
4. No history of HIV being HIV positive;
5. No active Hepatitis B or Hepatitis C infection.
* Life expectancy ≥ 12 weeks.
* Women of childbearing potential (WOCBP) must use study specified contraception.
* WOCBP demonstrate negative pregnancy test.
* Not breastfeeding.
* Men sexually active must use study specified contraception.

Exclusion Criteria:

* Use of chemotherapeutic agents or experimental agents for MDS within 14 days of the first day of study drug treatment.
* Use of erythroid stimulating agents, Granulocyte-colony stimulating factor (G-CSF), or Granulocyte-macrophage colony-stimulating factor (GM-CSF) within 14 days of the first day of study drug treatment, or during the study.
* Mean triplicate heart rate-corrected QT interval (QTc) \> 500 msec.
* Any of the following cardiac abnormalities:

1. QT interval \> 480 msec corrected using Fridericia's formula;
2. Risk factors for Torsade de Pointes;
3. Use of medication that prolongs the QT interval;
4. Myocardial infarction ≤ 6 months prior to first day of study drug treatment;
5. Unstable angina pectoris or serious uncontrolled cardiac arrhythmia.
* Any serious or uncontrolled medical disorder.
* Prior malignancy within the previous 3 years except for local cancers that have been cured.
* Subjects with a condition requiring systemic treatment with either corticosteroids (\> 10 mg daily prednisone equivalents) or other immunosuppressive medications within 14 days of study drug administration. Inhaled or topical steroids, and adrenal replacement doses \> 10 mg daily prednisone equivalents are permitted in the absence of active autoimmune disease.
* Use of other investigational drugs within 30 days of study drug administration.
* Major surgery within 4 weeks of study drug administration.
* Live-virus vaccination within 30 days of study drug administration.
* Allergy to study drug component.