A Phase 2 Open-label Study to Evaluate the Activity of Etavopivat on Transcranial Doppler Velocities in Pediatric Patients With Sickle Cell Disease Who Are at Increased Risk for Primary Stroke

Change in the timed-average-mean-maximum-velocity (TAMMV) arterial cerebral blood flow of index artery (L/R internal carotid artery [ICA], L/R middle cerebral artery [MCA]) at Week 12 versus baseline, as measured by TCD

The study will test a new medicine, etavopivat, for sickle cell disease and see if it is safe
 and helpful for participants with sickle cell disease who are at an increased risk of stroke.
 Participants will be divided into two cohorts depending on their transcranial doppler (TCD)
 ultrasound results and whether or not they receive hydroxyurea (medication that they may
 already be taking). In one cohort, participants with conditional transcranial doppler (TCD)
 or participants with abnormal TCD who are not able to receive hydroxyurea will be included.
 The study doctor will determine if the TCD result is conditional or abnormal. In another
 cohort, participants with conditional TCD or participants with abnormal TCD who are receiving
 a stable dose of hydroxyurea will be included. The study doctor will determine if the TCD
 result is conditional or abnormal. The participant will start a 52-week (1 year) treatment
 period. The participant will take 400 milligrams (mg) of etavopivat once a day for the 52
 weeks. The dose of 400 mg will be taken as 2 tablets by mouth, each containing 200 mg of
 etavopivat. Etavopivat may be taken with or without food. Each dose should be taken with a
 glass of water. As part of the study, the participants will be asked to visit the clinic
 frequently. At the end of the study, if deemed appropriate by you, your child, and the study
 doctor, your child may be offered the opportunity to participate in a separate study to
 continue receiving etavopivat.