CFTR and cystic fibrosis: By applying several recently described PE improvements to the CFTR F508del correction strategy, we achieved up to 11%, 58% and 25% mean F508del correction in HEK293T cells, 16HBEge-F508del cells and primary airway epithelial cells from patients with CF, representing 26-fold, 140-fold and 59-fold improvements in F508del correction over the original PE3 editing attempt, respectively.