Lipid Nanoparticles Deliver Full CFTR Gene in Cystic Fibrosis Gene Therapy Advance

UCLA researchers have developed a lipid nanoparticle-based gene-editing approach capable of inserting an entire healthy gene into human airway cells, restoring key biological function in a laboratory model of cystic fibrosis and establishing a potential new path toward mutation-agnostic gene therapy for inherited lung diseases. The study, published in Advanced Functional Materials, shows that lipid nanoparticles can be engineered to carry the complex molecular cargo required for precise insertion of a large full-length gene into the genome without using viral vectors.

"This work shows that we can package everything needed for precise gene insertion into a single, non-viral delivery system. That's a critical step toward developing gene therapies that can work across many different disease-causing mutations," said the senior author of the study, a member of the UCLA Broad Stem Cell Research Center.

Cystic fibrosis is caused by mutations in a single gene, the cystic fibrosis transmembrane conductance regulator, or CFTR, which encodes a channel that helps move chloride and water across the surface of airway cells. When the channel does not function properly, mucus in the lungs becomes thick and sticky, trapping bacteria and leading to chronic infections and progressive lung damage. Although highly effective drugs known as CFTR modulators have transformed care for many people with cystic fibrosis, about 10% of patients produce little or no CFTR protein at all, leaving nothing for those drugs to act on.

"For those patients, gene therapy isn't just an improvement - it's really the only option," said a co-author of the study and associate director of translational research at the stem cell center. "You have to give the cell the ability to make the protein in the first place."

Since there are over 1,700 different mutations in the CFTR gene that can cause cystic fibrosis, the team looked to develop a universal approach that could correct any of these errors in a single edit rather than individually. Most experimental gene therapies rely on viral vectors to deliver genetic material into cells. While powerful, viral approaches can be costly to manufacture, limited in the amount of genetic material they can carry and difficult to administer more than once because the immune system can recognize and react to them.

The UCLA team instead used lipid nanoparticles as a non-viral delivery system. The particles were engineered to transport three gene-editing components simultaneously: CRISPR machinery to cut DNA at a precise location, guide molecules to target the correct genomic site, and a DNA template encoding a full, functional copy of the CFTR gene.

"Getting all of that into a single particle - especially a gene as large as CFTR - is something that hadn't been shown before," said the study's first author and a recent Ph.D. graduate from the Jonas lab at UCLA. "If you can solve the 'big gene' problem, it opens the door for a lot of other diseases as well."

The researchers tested the system in lab-grown human airway cells carrying a severe cystic fibrosis mutation that does not respond to existing drugs. The nanoparticles successfully delivered a healthy CFTR gene into about 3–4% of the cells. Despite that relatively small fraction of corrected cells, the treatment restored between 88% and 100% of normal CFTR channel function across the cell population.

The researchers say the strength of that recovery reflects not just where the gene was inserted, but how it was engineered. The replacement CFTR gene was designed to maximize protein production once it entered the cell, enabling even a small number of corrected cells to have an outsized effect. That gene design - known as codon optimization - was developed by collaborators in a UCLA lab and boosts CFTR protein production without altering the protein itself.

Unlike approaches that deliver messenger RNA - which must be repeatedly re-dosed - the new strategy inserts the corrected gene directly into the genome, potentially allowing cells and their descendants to continue producing functional CFTR over time. For long-term benefit, however, gene editing ultimately needs to reach airway stem cells, which sit deep within the lung's protective lining and regenerate the airway throughout a person's life.

"These stem cells are long-lived and constantly regenerate the airway," said a co-author who is also a professor of pediatrics and pulmonary medicine at the David Geffen School of Medicine at UCLA. "If you can correct them, you could, in theory, have a lasting source of healthy cells."

Reaching those cells remains one of the biggest challenges ahead. The airway is designed to block foreign particles, and in patients with cystic fibrosis, thick mucus creates an additional barrier.