Nonclinical evaluation of renizgamglogene autogedtemcel for SCD and TDT

Sickle cell disease and transfusion-dependent β-thalassemia can be treated by fetal hemoglobin upregulation. Disruption of the distal BCL11A binding site at the HBG1/2 promoters to induce fetal hemoglobin using either SpCas9 or AsCas12a mimics multiple hereditary persistence of fetal hemoglobin mutations. AsCas12a showed higher editing efficiency, higher specificity, and increased fetal hemoglobin induction potential compared with SpCas9. AsCas12a-edited healthy donor CD34⁺ cells exhibited long-term, multi-lineage, and polyclonal engraftment in immunocompromised mice. High-level fetal hemoglobin induction was observed in erythroid progeny derived in vivo from edited healthy donor CD34⁺ cells and sickle cell disease or transfusion-dependent β-thalassemia donor CD34⁺ cells in vitro. In erythroid cells from patients with sickle cell disease, gene editing reduced sickling and improved rheological behaviors under deoxygenated conditions. In erythroid cells from patients with β-thalassemia, gene editing ameliorated ineffective erythropoiesis and significantly increased hemoglobin content per cell. A comprehensive off-target editing evaluation in edited CD34⁺ cells showed AsCas12a to be highly specific, with no off-target editing detected. In summary, editing CD34⁺ cells at the HBG1/2 promoter distal BCL11A binding site using AsCas12a phenocopied hereditary persistence of fetal hemoglobin mutations, demonstrating its potential as a gene editing approach for the treatment of β-hemoglobinopathies.