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.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 1/16/24. Questions regarding updates should be directed to the study team contact.