Study of the Effect of Etavopivat on Cerebral Hemodynamic Response in Children With Sickle Cell Disease

Inclusion Criteria: * Homozygous hemoglobin SS (HbSS) or hemoglobin S/beta0 thalassemia (HbS/β0 thal) * Hemoglobin (Hb): Hb ≤ 9.0 g/dL at baseline * Concomitant hydroxyurea (HU) therapy is allowed if the dose has been stable for at least 3 months with no anticipated need for dose adjustments during the study and no sign of hematological toxicity Exclusion Criteria: * Any one of the following requiring a medical facility visit within 14 days prior to signing the informed consent form: * Vaso-occlusive crisis (VOC) * Acute chest syndrome (ACS) * Splenic sequestration * Dactylitis * Requires chronic transfusion therapy * Abnormal TCD in the last 12 months * RBC transfusion within 60 days of screening * Severe renal dysfunction at the Screening Visit or on chronic dialysis * Hepatic dysfunction * Clinically relevant cardiac or pulmonary disease- e.g., congenital heart defect, uncompensated heart failure, or any unstable cardiac condition, arrhythmic heart condition, pulmonary fibrosis, pulmonary hypertension * Major surgery involving the stomach or small intestine * Chemotherapy or radiation within the past 2 years * History of overt clinical stroke within previous 2 years or any history of an intracranial hemorrhage * Clinically significant bacterial, fungal, parasitic, or viral infection currently receiving or that will require therapy * Female who is breast feeding or pregnant