Gene-modified CD34+ cells(St. Jude Children's Research Hospital)

This study is being done to test the safety of a new treatment called gene editing in Sickle Cell Disease (SCD) patients and to see if a single dose of this genetically modified cellular product will increase the amount of a certain hemoglobin called fetal hemoglobin (HbF) and help reduce the symptoms of SCD.
Primary Objective
* To assess the safety of autologous infusion of clustered regularly interspaced palindromic repeats (CRISPR)/ CRISPR associated protein (Cas9)-edited CD34+ hematopoietic stem and progenitor cells (HSPCs) in patients with severe SCD.
Secondary Objective
* To assess the efficacy autologous infusion of CRISPR/Cas9 genome-edited CD34+ HSPCs into patients with severe SCD.