This study is being conducted to assess safety and efficacy of bone marrow transplant in severe and less severely affected children. In this study, we will transplant bone marrow or cord blood from a HLA-matched brother or sister instead of the currently more common method with a HLA-identical sibling donor. This is a multicenter, single arm trial for patients between 2 and 10 years of age who have less severe HbSS or sickle beta zero thalassemia. Patient must have an HLA identical sibling donor who is less than 10 years old and who does not have HbSS, SC or sickle beta zero thalassemia.

This is a research study to find out if a study drug called EDIT-301 is safe and effective in treatment of patients with severe Sickle Cell Disease (SCD). The EDIT-301 study medicine is a new investigational therapy, which in this case means this is first-in-human use of this study drug. This study medication uses patients' own stem cells, modifies the cells with genetic modification, and transplants them back to the patient (by infusion) to treat SCD.
Participation in this study is expected to last approximately 30 months, including time for screening, collection of cells, transplant, and a 24 month follow-up period after transplant. At the end of that 24 month follow-up, the participant will be asked to participate in an additional long-term follow-up study, totaling 15 years of post-transplant follow-up.

This is a research study to find out if the study drug called BEAM-101 is safe and effective in the treatment of patients with severe Sickle cell disease (SCD). The study drug, BEAM-101 is a new investigational (experimental) therapy that is the first in human use of this drug.

The study medication uses patients' own stem cells that are harvested through apheresis (process where blood is removed, stem cells collected and blood is returned), changed by genetic modification, and transplanted back into the individual through intravenous infusion to treat severe SCD.

Participation in this study is expected to last approximately 24 months, starting at time of screening, through the collection of cells, transplantation of study drug, and 15-month follow-up period. Study visits during the screen and mobilization period will vary depending on the cell collection process, in other words, the mobilization and collection period could be 3 separate visits to harvest adequate stem cells. Subjects are then hospitalized for the conditioning period, transplantation of study drug and engraftment period (when blood counts return to normal). The follow up visits after discharge from the hospital will be monthly for the first 6 months, then every other month until 24 months post transplant period.

At the end of the 24 months, all participants will be asked to enroll in the long-term extension study for a duration of 13 years making the total follow-up period of 15 years.