This study looks at how long red blood cells (RBCs) last in people with sickle cell disease (SCD) who regularly receive blood transfusions. SCD is a blood disorder that causes RBCs to change shape and break down. This can lead to problems like strokes. Regular blood transfusions help by adding healthy RBCs to the blood. In this study, a small portion of the transfused RBCs will be labeled with a safe marker called biotin. Participants will return for check-ups on Day 1, weekly for 3 months, and then monthly for another 3 months to see how long these marked RBCs survive. There is also an optional study using a special type of treated RBC called INTERCEPT RBCs.

• Participants need to visit the clinic multiple times over 6 months.
• This study involves using a special marker to track RBC survival.
• An optional part of the study uses a different type of treated blood cells.