This study is looking at a new way to treat sickle cell disease (SCD), a condition where red blood cells are shaped like a sickle and can cause pain and other health issues. The treatment involves using a special gene therapy called **BAH243**. This study is open to people aged 2 to 50 years old with SCD.

Participants will be part of the study for up to 2 years after their stem cell transplant. They might also be asked to join a longer follow-up study for 13 more years. This will help doctors understand how safe and effective the treatment is over time. The study is designed to be as safe as possible, with careful checks before moving on to new participants.

• The study lasts up to 15 years in total.
• Participants must have specific types of SCD and meet certain health conditions.
• There are potential risks and benefits, which should be discussed with your doctor.