The purpose of this research study is to learn more about the safety and effects of CTX001 (the “Study Product”) in patients ages 12 to 35 years who have been diagnosed with severe sickle cell disease.

 A gene in stem cells will then be edited to help the stem cells make more fetal hemoglobin. Higher levels of fetal hemoglobin can improve red blood cell sickling.

This Phase 2 clinical research study is evaluating the safety and effectiveness of a once-daily oral investigational medicine that may improve anemia and reduce the need for red blood cell (RBC) transfusions among some patients who are chronically transfused.