This research is for people with severe Sickle Cell Disease (SCD), a blood disorder where red blood cells get misshaped and cause pain. The study will test a treatment that changes genes in blood stem cells. These stem cells are called **CD34+ Hematopoietic Stem Cells**. They will be taken from the participant, fixed to make normal hemoglobin (**HbA**), and then returned through an **IV infusion** after strong medicine helps prepare the body.
**Key Points:**
- Participants must be between 12 and 40 years old.
- The study involves a treatment that uses your own stem cells.
- Participants cannot have had previous stem cell transplants or gene therapy.
Eligible participants need to have had multiple SCD crises or complications, like **VOC** (pain crises) or **ACS** (lung problems). They should also have a good performance status, meaning they can do daily activities well. Some risks include not having a matching sibling donor or prior health issues like cancer or infections. It's important for those interested to discuss all risks and benefits with their doctor.