New approach to delivering gene therapy for cystic fibrosis

A lipid nanoparticle-based gene therapy for cystic fibrosis restores biological function in a preclinical model.

Researchers at the University of California Los Angeles (UCLA), California, have developed an approach that helps correct the activity of a membrane channel known as cystic fibrosis transmembrane conductance regulator (CFTR) in lab-grown human airway cells. Instead of using viral vectors, the scientists engineered lipid nanoparticles to deliver genome-editing components and a full-length CFTR gene template into the cells. This research represents a potential step towards developing gene therapies for diseases caused by a wide range of mutations.

'For patients who currently have no effective treatments… This kind of work represents hope – not because it will be ready tomorrow, but because it shows a path forward,' said Professor Brigitte Gomperts, co-author of the study published in Advanced Functional Materials.

The CFTR gene encodes a channel that regulates ion transport in lung epithelial cells, with more than 1000 CFTR gene variants confirmed to cause cystic fibrosis, an inherited lung disease, according to the CFTR2 database. A dysfunctional or absent channel results in impaired mucociliary clearance and the build-up of sticky, dehydrated mucus within the lungs, trapping bacteria and leading to chronic infections and progressive damage. While CFTR modulator drugs benefit approximately 90 percent of patients with cystic fibrosis, the remaining ten percent lack effective therapies.  

UCLA researchers engineered lipid nanoparticles large enough to encapsulate the complete genome-editing machinery: CRISPR/Cas9 to cut at the precise gene location, a guide RNA for accurate targeting and a linear DNA template of a full, healthy copy of CFTR for insertion via homology-directed repair.

The therapy successfully integrated a functional CFTR gene into approximately three to four percent of human airway epithelial cells carrying the severe G542X mutation. Despite this small proportion of edited cells, CFTR channel function was restored in 88 to 100 percent of the cell population. This was achieved through codon optimisation, an approach which boosts the production of a protein without altering its amino acid sequence.

'Getting all of that into a single particle – especially a gene as large as CFTR – is something that hadn't been shown before,' said Dr Ruth Foley, the first author of the study. 'If you can solve the "big gene" problem, it opens the door for a lot of other diseases as well.'

This gene therapy approach could extend beyond cystic fibrosis to other conditions caused by mutations in large, single genes. Lipid nanoparticles avoid limitations of viral vectors, including a more affordable manufacturing process and a lower risk of immune reaction following repeated dosing.

The next step is targeting airway stem cells to provide a lifelong source of healthy epithelium. The challenge is that these cells reside deep within the lung epithelium, with thick mucus in cystic fibrosis patients imposing an additional barrier.