MT2023-29: Long-term Follow-up of Subjects With Sickle Cell Disease Treated With ExVivo Gene Therapy Using Autologous Hematopoietic Stem Cells Transduced With a Lentiviral Vector

The purpose of this study is to evaluate the long-term safety and ability of a transplant with gene modified stem cells (autologous stem cell transplant) to treat sickle cell disease. Participants must have received investigational gene therapy with bb1111 in a clinical study sponsored by bluebird bio. There is no additional treatment associated with this study as this is a long-term follow-up study.