Inclusion Criteria:

• Diagnosis of severe aplastic anemia (bone marrow cellularity < 30%, with two of three peripheral counts at the time of initial presentation or currently low with ANC < 500/mL, pre-transfusion PLT< 20,000/mL, or pre-transfusion hemoglobin < 8 g/dL and presence of no other underlying disorder.
• Diagnosis of MDS (WHO) with bone marrow cellularity < 30%, with two of three peripheral counts at the time of initial presentation or currently low with ANC < 500/mL, pre-transfusion PLT < 20,000/mL, or pre-transfusion hemoglobin < 8 g/dL.
• Patients with MDS who have received prior biological therapy (not chemotherapy) are eligible. Hypomethylating agents and histone deacetylase inhibitors are considered as biological therapy.
• Age 15 or greater
• Adequate renal function (creatinine less than or equal to 2.0 mg/dL) unless related to the disease
• Adequate hepatic function (bilirubin less than or equal to 3.5 mg/dL) unless related to the disease
• No other investigational therapy in the past 14 days
• Able to sign consent form
• Able to comply with the need for contraception (abstinence, condom, birth control pill, or other acceptable form of contraception) during the entire study period
• Diagnosis of MDS (WHO) with bone marrow cellularity greater than 30%, with low or intermediate-1 risk by the IPSS score, and requiring treatment (i.e. transfusion-dependent)

Exclusion Criteria:

• Active and uncontrolled infection
• HIV positive test
• Pregnant or breast feeding
• Active and uncontrolled medical illness (pulmonary, cardiac, neurological, or other) that in the opinion of treating physician would likely interfere with study treatment