Prime Editing Corrects Cystic Fibrosis Mutation

David Liu and colleagues at the Broad Institute presented yesterday the systematic optimisation of PE for correcting the cystic fibrosis transmembrane conductance regulator (CFTR) F508del mutation, a primary cause of CF.

The researchers combined several efficiency enhancements, including engineered PE guide RNAs and PEmax architecture, achieving a high correction efficiency in immortalised bronchial epithelial cells and substantial correction in patient-derived airway epithelial cells.

They used engineered PE guide RNAs (pegRNAs) protected from exonuclease degradation, the PEmax architecture, and transient expression of a dominant-negative mismatch repair protein to inhibit cellular repair mechanisms that could compromise editing efficiency.

Additionally, they employed strategic silent edits to evade cellular mismatch repair and incorporated PE6 variants and dead single-guide RNAs (dsgRNAs) to improve targeting and editing efficiency.

The results demonstrated that these combined optimisations significantly increased the correction efficiencies for CFTR F508del, reaching 58% in immortalised bronchial epithelial cells and 25% in primary airway epithelial cells derived from CF patients.

Functional assays indicated that the corrected CFTR ion channels restored over 50% of wild-type function, comparable to current CF drug treatments.

These findings suggest that the refined PE approach could offer a durable, one-time treatment for CF, pending the development of effective in vivo delivery systems.

David Liu led the study at the Broad Institute of MIT and Harvard, USA. It was published in Nature Biomedical Engineering on July 10, 2024.