**Gene Editing for Sickle Cell Disease Study** This study explores a new treatment called *gene editing* for Sickle Cell Disease (SCD), a condition where red blood cells are sickle-shaped instead of round, causing health issues. The treatment aims to increase fetal hemoglobin (HbF) to reduce SCD symptoms by editing genes using CRISPR/Cas9, a tool that changes genes in cells. Participants will receive a medicine called motixafortide to help move special cells called hematopoietic stem and progenitor cells (HSPCs) into their blood. If motixafortide isn't suitable, plerixafor will be used instead. These cells are collected and edited in a lab. After editing, participants receive a chemotherapy drug called Busulfan before the gene-edited cells are given back to them. The study lasts 3 years, with an additional 12-year follow-up. **Key Points:** - Participation involves 3 years of follow-up, plus a further 12-year long-term follow-up study. - Participants must be 18-24.9 years old with specific SCD conditions and meet other health criteria. - The study includes using chemotherapy and requires specific medicines to prepare cells for gene editing.