Cystic fibrosis is a prevalent genetic disorder that leads to the accumulation of thick mucus in the lungs and other body parts, causing breathing difficulties and infections. A groundbreaking gene-editing technique has been created to effectively correct the most common mutation responsible for cystic fibrosis, affecting 85% of patients. This innovation shows promise for future treatments that could be administered once and result in fewer side effects. The new method accurately and long-lastingly fixes the mutation in human lung cells, restoring cell functionality similar to the effects of Trikafta.
Researchers at the Broad Institute of MIT and Harvard and the University of Iowa have devised a gene-editing strategy that targets the predominant mutation causing cystic fibrosis, affecting 85% of patients. This breakthrough could potentially revolutionize the way treatments are developed, offering single-administration options with reduced side effects.
This novel method, featured in a recent issue of Nature Biomedical Engineering, offers precise and enduring correction of the mutation in human lung cells, resulting in functional restoration comparable to that achieved by Trikafta. The technique is rooted in prime editing, a method capable of making diverse alterations in the genome, such as insertions, deletions, and substitutions, with minimal unintended consequences. Prime editing was introduced in 2019 by David Liu’s laboratory, the Richard Merkin Professor and Director of the Merkin Institute of Transformative Technologies in Healthcare at the Broad Institute, also serving as a professor at Harvard University and an investigator at the Howard Hughes Medical Institute.
“The potential of prime editing to rectify the primary cause of cystic fibrosis and potentially offer a permanent solution for this severe condition is promising,” noted Liu, the senior researcher on the project. “Devising an efficient method to correct this challenging mutation not only sets a path for addressing cystic fibrosis but also lays the groundwork for precision corrections of other mutations causing debilitating diseases.”
The primary authors of the study were postdoctoral researcher Alex Sousa and graduate student Colin Hemez, both affiliated with Liu’s laboratory.
Genetic Restoration
Cystic fibrosis stems from mutations in the CFTR gene, disrupting ion channels responsible for transporting chloride out of cells across the cell membrane. With over 2,000 identified CFTR gene variants, 700 lead to diseases. The most prevalent mutation involves a three-base-pair CTT deletion, triggering misfolding and degradation of the ion channel protein.
Addressing the CTT deletion in CFTR has been a longstanding goal of gene-editing therapies pursued by various research groups, including Liu’s. Previous attempts, often involving CRISPR/Cas9 nuclease editing that induces double-stranded DNA breaks, have fallen short due to insufficient efficiency or the risk of generating undesired alterations in the target gene and elsewhere in the genome.
Prime editing emerges as a more versatile and controlled form of gene manipulation that eliminates the need for double-stranded breaks, offering a promising solution to this challenge. To amplify the effectiveness of correcting the CFTR mutation, Liu’s team incorporated six enhancements to the technology. These enhancements included refining the prime editing guide RNAs that govern prime editor proteins to locate and execute the necessary edit, as well as modifying the prime editor protein itself and other adjustments to enhance target site accessibility. Cumulatively, these enhancements successfully rectified approximately 60% of CTT deletions in human lung cells and about 25% in cells directly obtained from patient lungs and cultured, surpassing earlier methods that corrected less than 1% of the mutation in cells. Moreover, this new approach resulted in 3.5 times fewer unintended insertions and deletions per correction compared to previous methods employing the Cas9 nuclease enzyme.
Future research will focus on developing methods to package and deliver the prime editing system to the airways of mice and eventually humans. Recent advancements, such as lipid nanoparticles capable of reaching mouse lungs, offer promise for accelerating the translation of this innovative approach.
