A Phase 3, Multicenter, Randomized, Double-blind Study to Compare the Efficacy and Safety of Oral Azacitidine Plus Best Supportive Care Versus Placebo Plus Best Supportive Care in Subjects With Red Blood Cell Transfusion-dependent Anemia and Thrombocytopenia Due to IPSS Lower-risk Myelodysplastic Syndromes

Inclusion Criteria:

- 18 years or older

- Have a documented diagnosis of MDS

- Anemia that requires red blood cell transfusions

- Thrombocytopenia (sustained for at least 21 days) within 14 days prior to
randomization

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

- Must agree to follow pregnancy precautions as required by protocol.

- Must be willing to consent to two or more bone marrow aspirate procedures to be
completed during study.

Exclusion Criteria:

- Secondary or hypoplastic MDS or other subtype with eligibility for treatment with
immunotherapy

- Prior treatment with azacitidine, decitabine, other hypomethylating agents and
lenalidomide

- Prior allogeneic or autologous stem cell transplant

- Eligible for allogenic or autologous stem cell transplant

- History of inflammatory bowel disease (eg, Crohn's disease, ulcerative colitis),
celiac disease (ie, sprue), prior gastrectomy or upper bowel removal, or any other
gastrointestinal disorder or defect

- Thrombocytopenia secondary to other possible causes, including medication(s),
congenital disorder(s), immune disorder(s), or microvascular disorder(s)

- Use of cytotoxic, chemotherapeutic, targeted or investigational agents/therapies,
thrombopoiesis-stimulating agents (TSAs), erythropoiesis-stimulating agents (ESAs)
and other red blood cell hematopoietic growth factors, and within 28 days prior to
randomization

- Ongoing adverse events from previous treatment, regardless of the time period

- Concurrent use of iron-chelating agents, (except for subjects on a stable dose for at
least 8 weeks (56 days) prior to randomization), corticosteroid (except for subjects
on a stable or decreasing dose for ≥ 1 week prior to randomization for medical
conditions other than MDS)

- Prior history of cancer, other than MDS, unless the subject has been free of the
disease for ≥ 3 years. (Basal or squamous cell carcinoma of the skin, carcinoma in
situ of the cervix, carcinoma in situ of the breast, and incidental histologic
finding of prostate cancer) (T1a or T1b using the tumor, nodes, metastasis [TNM]
clinical staging system is allowed)

- Significant active cardiac disease within the previous 6 months

- Uncontrolled systemic fungal, bacterial, or viral infection

- Known Human Immunodeficiency Virus (HIV) or Hepatitis C (HCV) infection, or evidence
of active Hepatitis B Virus (HBV) infection

- Known clinically significant anemia due to iron, vitamin B12, or folate deficiencies,
or autoimmune or hereditary hemolytic anemia, or gastrointestinal bleeding

- Abnormal coagulation parameters

- Abnormal liver function test results

- Abnormal kidney function test results

- Known or suspected hypersensitivity to azacitidine or mannitol

- Any significant medical condition, laboratory abnormality, or psychiatric illness