Study of SX-682 Alone and in Combination With Oral or Intravenous Decitabine in Subjects With Myelodysplastic Syndrome

Inclusion Criteria:

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

1. International Prognostic Scoring System (IPSS) low risk or intermediate-1 riskpatients without 5q deletion: i. Dose escalation portion: failed prior treatment with at least 4 cyclesstarted of a hypomethylating agent (HMA; azacitidine or decitabine) defined asno response to treatment, loss of response at any time point, or progressivedisease/intolerance to therapy. ii. Dose expansion portion: failed prior treatment defined as no response totreatment with at least 4 cycles started of HMA, loss of response at any timepoint, or progressive disease/intolerance to therapy ("HMA failure"); or noprior treatment with HMA ("HMA naive").

2. IPSS low risk or intermediate-1 risk patients with 5q deletion: i. Dose escalation portion: failed prior treatment with at least 4 cyclesstarted of lenalidomide and 4 cycles of hypomethylating agent (azacitidine ordecitabine) defined as no response to treatment, loss of response at any timepoint, or progressive disease/intolerance to therapy. ii. Dose expansion portion: same as non-del(5q) lower risk cohort + requirementof failed prior treatment with lenalidomide defined as no response to treatmentwith at least 4 cycles started of lenalidomide, loss of response at any timepoint, or progressive disease/intolerance to therapy.

3. IPSS intermediate-2 risk or high risk patients: HMA failure or HMA naïve asdefined above.

• 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 timesupper 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 thefirst 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 thefirst 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 with the exception of drugsthat are considered absolutely essential for the care of the subject;

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 2 years except for local cancers that have beencured; or patients who have been adequately treated and have low risk ofreoccurrence.

• 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 adrenalreplacement doses > 10 mg daily prednisone equivalents are permitted in the absenceof 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.