Pharmacokinetics and Safety of Endari (L-glutamine) in Sickle Cell Disease Patients

Inclusion Criteria: 1. 5 years of age and older at Screening. 2. Has documented diagnosis of SCD with known genotype (HbSS, HbSβ0 and HbSC). 3. Written informed consent provided by patient or the patient's legally authorized representative. 4. Non-pregnant females of childbearing age must agree to avoid pregnancy during the study and to practice a recognized form of birth control during the course of the study (e.g., barrier, birth control pills, or abstinence). Inclusion Criteria for Healthy Volunteers: 1. No known hematologic illness. 2. No known renal impairment. 3. 18 Years of age or older at screening. 4. Written informed consent provided by patient or the patient's legally authorized representative. 5. African American and Hispanic participants preferred. Exclusion Criteria: 1. Recent significant medical condition that required hospitalization (other than sickle cell crisis) within 2 months prior to starting L-glutamine therapy. 2. History of chronic kidney disease Stage 4 (glomerular filtration rate \[GFR\]=15-29) or Stage 5 (GFR\<15 mL/min/1.73 m2). 3. History of chronic liver disease Child Pugh class C (10-15 points). 4. Received any blood products 3 months prior to starting L-glutamine therapy. 5. Currently pregnant or lactating or planning to conceive during the study period. 6. Currently taking or has taken any form of glutamine supplement within 30 days prior to starting L-glutamine therapy. 7. Has been treated with an investigational medication/treatment within 30 days prior to starting L-glutamine therapy. 8. Is currently enrolled in an investigational drug or device study and/or has participated in such a study within 30 days prior to starting L-glutamine therapy. 9. Factors that would, in the judgment of the investigator, make it difficult for the patient to comply with study requirements. 10. Patient is currently being treated with crizanlizumab or voxelotor. Exclusion Criteria for Healthy Volunteers: 1. Known allergies to L-glutamine. 2. Informed consent document was not completed and signed. 3. Currently pregnant or lactating or planning to conceive during the study period. 4. Known hematologic illness, renal or hepatic impairment. 5. Received any blood products within 3 months of starting L-glutamine therapy.