In Vivo Gene Editing of Lung Stem Cells Achieves Long-Term Correction for Cystic Fibrosis

In this study, highly efficient lung-targeting lipid nanoparticles (LNPs) were harnessed to deliver CRISPR-Cas9 and adenine base editors (ABEs) to lung stem cells in a mouse CF disease model. The method achieved 70% genome editing efficiency and sustained gene expression for an extended period of more than 660 days. Over 95% of cystic fibrosis transmembrane conductance regulator (CFTR) DNA was corrected, restoring CFTR protein function to levels on par with current CF therapies.

"Scientists have previously shown that genome editing in the liver is durable, but it was unknown whether the lungs had this capacity. Here, we discovered that lung-targeting lipid nanoparticles can deliver gene correction technologies to lung stem cells, which then differentiate into a healthy epithelium," says Daniel Siegwart, who led the study at the University of Texas Southwestern Medical Center.

The lung-selective organ targeting (SORT) LNPs were administered intravenously, ensuring efficient delivery to lung stem cells and overcoming barriers posed by mucus and macrophages. This non-viral approach not only ensures safety by mitigating risks associated with traditional viral delivery methods, such as immune responses and insertional mutagenesis but also paves the way for more effective treatments.

The long-term persistence of gene edits highlights the potential for this approach in treating genetic lung diseases. In addition to CF, the methodology shows promise for addressing a variety of genetic disorders affecting the lungs by achieving sustained correction in tissue-resident stem cells.

Specifically, the study focused on the R553X mutation in the CFTR gene, a common mutation in cystic fibrosis patients that introduces a premature stop codon, leading to a non-functional protein. The researchers utilised an ABE encapsulated in the LNPs to convert the adenine at position 553 to guanine. The intervention corrected the R553X nonsense mutation to the typical sequence that codes for a functional CFTR protein.

"If this finding can be translated to humans, then correction of disease-causing CFTR mutations would likely provide a long-lasting therapy for CF lung disease. The described approach may have the most immediate implications for people with nonsense mutations in CFTR," Daniel Siegwart explains, pointing to the approximately 200 known mutations that introduce a stop codon and lead to a truncated CFTR protein.

This correction was achieved in over 50% of lung stem cells in CF mouse models, significantly restoring CFTR function. The success was further validated in human bronchial epithelial cells derived from CF patients, showing substantial CFTR protein restoration and function, similar to levels achieved by the current standard of care, Trikafta.

"Before entering into the clinic, the approach would have to be deemed very safe and effective in a variety of preclinical models, including non-human primates. Most importantly, regulatory drug review and approval bodies would further review the justification for a potential medicine with high safety and ethical standards," concludes Daniel Siegwart.

Daniel Siegwart led the research at the University of Texas Southwestern Medical Center. It was published today in Science and is also mentioned in a related perspective.