Inclusion Criteria

Key Inclusion Criteria (Part 1 and Part 2):

- Diagnosis of MDS by bone marrow biopsy.

- International Prognostic Scoring System (IPSS) score of low or intermediate-1 risk
MDS.

- May have received prior therapy for MDS.

- Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0, 1 or 2.

- Adequate liver and renal function.

- Additional criteria exist.

Key Exclusion Criteria (Part 1 and Part 2):

- History of bone marrow transplant.

- Treatment for MDS other than transfusions or a stable dose (≥ 4 weeks) of
hematopoietic growth factors on the day of the first dose of study drug.

- Concomitant malignancies or previous malignancies with less than a 2-year
disease-free interval at the time of enrollment.

- Treatment with an investigational medicinal product that is not expected to be
cleared by the first dose of study drug or that has demonstrated to have prolonged
side effects.

- Treatment with azacitidine or decitabine within 2 weeks prior to first dose of study
drug.

- Chronic use (> 2 weeks) of greater than physiologic doses of corticosteroids (dose
equivalent to > 20 mg/day of prednisone) within 4 weeks prior to first dose of study
drug.

- Treatment with an immunomodulatory agent within 4 weeks prior to the first dose of
study drug.

- Additional criteria exist.