LOS ANGELES, Calif. – Researchers at UCLA have developed a nonviral gene-editing strategy that could help pave the way for one-time treatments for people with cystic fibrosis (CF).
The experimental therapy uses lipid nanoparticles — tiny fatty molecules — to insert a full, healthy copy of the CFTR gene into human airway cells, restoring protein function in laboratory tests.
“This work shows that we can package everything needed for precise gene insertion into a single, non-viral delivery system,” Steven Jonas, MD, PhD, senior author of the study and a member of the UCLA Broad Stem Cell Research Center, said in a UCLA press release detailing the team’s work in a lab model of CF.
According to Jonas, “That’s a critical step toward developing gene therapies that can work across many different disease-causing mutations.”
The study, “Lipid Nanoparticles for the Delivery of CRISPR/Cas9 Machinery to Enable Site-Specific Integration of CFTR and Mutation-Agnostic Disease Rescue,” was published in the journal Advanced Functional Materials.
CF is caused by mutations in the CFTR gene, which provides instructions for a protein channel also named CFTR that regulates the movement of chloride — salt — and water across the cell membrane. When the channel is missing or is dysfunctional, thick, sticky mucus builds up in the lungs, leading to infection, inflammation, and progressive damage.
A modern class of medications called CFTR modulators has helped enhance the functionality of the CFTR protein. In recent years, such treatments have dramatically improved outcomes for many people with CF.
However, about 10% of patients produce no or too little CFTR protein.
“For those patients, gene therapy isn’t just an improvement — it’s really the only option,” said Brigitte Gomperts, MD, coauthor 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.”
UCLA team working toward a universal gene therapy for CF
Given the more than 1,700 mutations associated with CF, the UCLA team aimed to design a universal gene therapy.
To date, modified viruses have been used in most gene therapies to carry genetic material into cells. But these have limitations, namely that the amount of genetic material they can deliver is limited. These viruses also can trigger an immune reaction that precludes redosing.
To overcome such hurdles, the researchers engineered lipid nanoparticles to carry three components of the gene-editing machinery: CRISPR — a gene-editing system that acts like molecular scissors to cut DNA at a precise spot — guide molecules for precise targeting, and a complete, healthy 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, PhD, the study’s first author. “If you can solve the ‘big gene’ problem, it opens the door for a lot of other diseases as well.”
When tested in lab-grown human airway cells with a severe CF mutation unresponsive to current therapies, the gene editing treatment inserted a healthy CFTR gene into approximately 3% to 4% of cells, the researchers noted.
The data showed that CFTR channel activity across the cell population was restored to between 88% and 100% of normal levels.
According to the researchers, this restoration was partly due to the way the replacement gene was engineered, as it was designed to maximize protein production once inside the cell. That enables an outsized effect from the small number of corrected cells, per the team.
Thick mucus in airways creates roadblock in delivering treatment
Importantly, by inserting a therapeutic gene directly into the genome, the new strategy may allow cells to continue producing working CFTR protein over time, with no need of redosing, the researchers noted.
For the effects to last, however, the gene editing therapy will need to reach airway stem cells located deep within the lung’s protective lining, which continually renew and repair lung tissue.
“These stem cells are long-lived and constantly regenerate the airway,” said Gompert. “If you can correct them, you could, in theory, have a lasting source of healthy cells.”
The thick mucus in the airways that is a hallmark of CF represents another difficulty in reaching those cells.
Jonas noted that “this paper is a proof of concept.” According to the scientist, also 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.”
Because lipid nanoparticles are adaptable and do not use viral components, the platform could eventually offer a more flexible, scalable, and affordable alternative to traditional gene therapies, according to the investigators.
“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.”
The investigators noted that this work is still in its early stages.
“Translation of the findings reported in this study will further require the development of methods to overcome delivery challenges notoriously facing CF-directed therapeutics,” the scientists wrote.
Looking toward, though, the scientists say this strategy perhaps may be extended to other inherited lung diseases — and potentially disorders affecting different organs — that are caused by a variety of mutations in large genes.
According to Gomperts, “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.”
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Steven Jonas, MD, PhD