The study is testing a new medicine called etavopivat to help people with sickle cell disease, a condition where red blood cells are shaped like a sickle and can block blood vessels, causing pain and damage. The goal is to see if etavopivat can reduce these pain crises, organ damage, and tiredness. Participants will either receive etavopivat or a placebo (a pill with no medicine), determined by chance. The study lasts about 2 years.

• Duration: The study will last for about 2 years.
• Participant Requirements: Ages 12 and up with sickle cell disease and 1-15 pain crises in the past year.
• Exclusions: More than 15 crises, certain medications or treatments like transfusions, liver or kidney issues.

Participants should not have had certain treatments recently and must have documented sickle cell disease. They cannot join if they have severe liver or kidney problems, or if they travel less than 100 meters in a walking test. This study helps find if etavopivat is effective and safe for sickle cell disease.