New gene editing approach offers hope for cystic fibrosis patients

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 - tiny fat-based particles widely used to deliver mRNA vaccines - 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."

Dr. Steven Jonas, senior author of the study and member, 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 Dr. Brigitte Gomperts, 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."

A new way to deliver a complete gene

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.

In this study, 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 Ruth Foley, 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 Dr. Donald Kohn's lab at UCLA and boosts CFTR protein production without altering the protein itself. 

Toward durable, one-time therapies

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 Gomperts, 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.

"This paper is a proof of concept," said Jonas, who is also an assistant professor of pediatrics at the medical school and a member of the California NanoSystems Institute. "It shows that we can package and deliver the right genetic cargo. The next challenge is getting it to the right cells in the body."

A platform with broader implications

Because lipid nanoparticles are modular and do not rely on viral components, the approach could be more flexible, scalable and potentially more affordable than traditional gene therapies.

"This kind of platform gives you room to iterate," Foley said. "If you need to re-dose or adapt the cargo for a different disease, you're not starting from scratch."

Beyond cystic fibrosis, the researchers say the strategy could be applied to other genetic lung diseases - and potentially conditions in other tissues - caused by large genes with many possible mutations.

"For patients who currently have no effective treatments," Gomperts said, "this kind of work represents hope - not because it will be ready tomorrow, but because it shows a path forward."

Additional authors include Paul G. Ayoub, Vrishti Sinha, Colin Juett, Alicia Sanoyca, Emily C. Duggan, Lindsay E. Lathrop, Priyanka Bhatt, Kevin Coote and Beate Illek.

The research was supported by the National Institutes of Health, the Cystic Fibrosis Foundation, the California Institute for Regenerative Medicine and the Cystic Fibrosis Research Institute.