Similarly, we achieved a frequency of 5% gene editing at the endogenous β-globin gene in human CD34+ haematopoietic progenitor cells treated once with SCF and γPNA/donor DNA NPs ex vivo, and we showed that these cells can engaft into NOD-scid IL2rγnull mice with persistent evidence of gene editing, supporting the eventual translatability of our approach to individuals with thalassaemia. Here, KITLG is linked to thalassemia.