This study is testing a new medicine called etavopivat for kids with a blood disorder known as sickle cell disease (SCD). SCD can cause blood cells to become sickle-shaped, which might block blood flow and increase the risk of a stroke (a sudden problem in the brain caused by a lack of blood flow). The study aims to check if etavopivat is safe and helpful for kids at higher risk of stroke. Participants will take two tablets (400 mg total) of etavopivat each day for a year. They may also join an optional 48-week extension to continue monitoring the medicine's safety. Participants must visit the clinic often and meet specific health criteria. Some children will be taking a medicine called hydroxyurea, which they may already be using to help manage SCD. The study involves kids aged 12 to 16 with certain health conditions.

• Participants will take etavopivat daily for 52 weeks, with the option to extend treatment by 48 weeks.
• Clinic visits are frequent to monitor safety and progress.
• Participants must meet specific health criteria, like stable blood counts and no previous strokes.