A Study of Nicotinamide With Oral Tetrahydrouridine and Decitabine to Treat High Risk Sickle Cell Disease

Inclusion Criteria:

• Age 18 years or older.

• Written informed consent provided by the subject before study entry.

• Confirmed sickle cell disease (SCD) as determined by hemoglobin electrophoresis orliquid chromatography.

• Subject is in his/her steady state and not having any acute complication due to SCD (i.e., hospitalization, acute pain, or acute chest syndrome in the past 14 days).

• Weight at least 40kg

• Regular compliance with comprehensive care and previous therapy.

• Symptomatic SCD is defined as having one of following, despite at least 6 months ofhydroxyurea therapy, or refuse to take hydroxyurea for personal reasons: fetalhemoglobin <0.5 g/dL, or 3 or more pain episodes per year requiring parenteralnarcotics, or 1 or more acute chest syndrome episodes, or Hemoglobin <9 g/dL andabsolute reticulocyte count <250,000/mm3.

Exclusion Criteria:

• Inability to give informed consent.

• Experienced severe sepsis or septic shock within the previous 12 weeks.

• Last HU dose was ingested within the previous 4 weeks.

• Currently pregnant or breast-feeding.

• Alanine Aminotransferase (ALT) ≥ 3 times the upper limit of normal or albumin <2.0mg/dL or direct (conjugated) bilirubin ≥ 1.5 mg/dl.

• Serum creatinine >2.9 mg/dL and calculated creatinine clearance <30 mL/min.

• Platelet count >800 x 109/L.

• Absolute neutrophil count <1.5 x 109/L.

• Female of active childbearing potential who is unwilling to use at least one of thetwo following forms of birth control: (i) not having heterosexual sexual contactbeginning at the screening visit and continuing until 4 weeks after the last dose ofdecitabine OR (ii) intrauterine device (IUD).

• Sexually active male who is unwilling to use a condom when engaging in any sexualcontact with a female with child-bearing potential, beginning at the screening visitand continuing until 4 weeks after taking the last dose of THU and decitabine. Thisrequirement applies also to males who have had a successful vasectomy.

• Altered mental status or recurrent seizures requiring anti-seizure medications.

• Moribund or any concurrent disease (e.g., hepatic, renal, cardiac, metabolic) ofsuch severity that death within 24 weeks is likely.

• Concurrent diagnosis of malignancy including known Myelodysplastic syndrome,leukemia, or an abnormal karyotype.

• New York Heart Association (NYHA) class III/IV status.

• Eastern Co-operative Oncology Group (ECOG) performance status ≥3.

• Participant is on chronic transfusion therapy

• Known history of illicit drug or alcohol abuse within the past 12 months.

• Other experimental or investigational drug therapy in the past 28 days.

• Taking l-glutamine within the last 28 days

• Being positive for HIV infection