Researchers have refined the primary editing (PE) method for correcting the F508del mutation in the cystic fibrosis transmembrane conductance regulator (CFTR), a significant cause of cystic fibrosis. They combined several efficiency improvements, including engineered PE guide RNAs and PEmax architecture. They achieved high correction efficiency in immortalized bronchial epithelial cells and substantial correction in patient-derived airway epithelial cells. In addition, they used strategic silent modifications to evade cellular mismatch repair and incorporated PE6 variants and dead simple guide RNAs (dsgRNAs) to improve targeting and editing efficiency. Results showed that these combined optimizations significantly increased the correction efficiency for CFTR F508del, reaching 58% in immortalized bronchial epithelial cells and 25% in primary airway epithelial cells derived from cystic fibrosis patients. Functional analyses indicated that corrected CFTR ion channels restored more than 50% of wild-type function, comparable to current drug treatments for cystic fibrosis.
