Editing the core region in HPFH deletions alters fetal and adult globin expression for treatment of f3-hemoglobinopathies

Reactivation of fetal hemoglobin (HbF) is a commonly adapted strategy to ameliorate 0-hemoglobinopathies. However, the continued production of defective adult hemoglobin (HbA) limits HbF tetramer production affecting the therapeutic ben-efits. Here, we evaluated deletional hereditary persistence of fetal hemoglobin (HPFH) mutations and identified an 11-kb sequence, encompassing putative repressor region (PRR) to 0-globin exon-1 (0E1), as the core deletion that ablates HbA and exhibits superior HbF production compared with HPFH or other well-established targets. PRR-0E1-edited hematopoi-etic stem and progenitor cells (HSPCs) retained their genome integrity and their engraftment potential to repopulate for long-term hematopoiesis in immunocompromised mice pro-ducing HbF positive cells in vivo. Furthermore, PRR-0E1 gene editing is feasible without ex vivo HSPC culture. Impor-tantly, the editing induced therapeutically significant levels of HbF to reverse the phenotypes of both sickle cell disease and 0-thalassemia major. These findings imply that PRR-0E1 gene editing of patient HSPCs could lead to improved thera-peutic outcomes for 0-hemoglobinopathy gene therapy.