Wave Life Sciences made headlines on October 16th as the first company to treat a genetic condition by editing RNA at the clinical level. This breakthrough highlights RNA editing's potential to address diseases where DNA editing faces limitations, offering a more flexible and potentially safer therapeutic approach. The rapid development of mRNA vaccines during the COVID-19 pandemic has already demonstrated the vital role RNAs play beyond gene expression and regulation.
The Science of RNA Editing
Cells synthesize messenger RNA (mRNA) using DNA instructions to create functional proteins. Errors during transcription can lead to faulty proteins and debilitating disorders. RNA editing allows scientists to correct these mRNA mistakes before protein synthesis. One key technique involves adenosine deaminase acting on RNA (ADAR) enzymes, which convert adenosine to inosine, mimicking guanosine. This triggers cellular mechanisms to correct the mRNA, restoring its original function and enabling the production of normal proteins.
Scientists use guide RNAs (gRNAs) to direct ADAR enzymes to specific mRNA locations. This site-specific RNA editing holds promise for treating various genetic conditions.
Clinical Applications and Development
Wave Life Sciences is using RNA editing to treat alpha-1 antitrypsin deficiency (AATD), an inherited disorder causing protein buildup affecting the liver and lungs. Their therapy, WVE-006, uses a gRNA to guide ADAR enzymes to single-point mutations in the SERPINA1 gene's mRNA, which provides instructions for producing α-1 antitrypsin. By correcting these mutations, cells can produce α-1 antitrypsin at normal levels.
"The ability to target specific RNA sequences with ADAR enzymes opens new avenues for treating genetic diseases," says Dr. [Name], lead researcher at Wave Life Sciences. "Our initial results with WVE-006 are promising, and we are eager to explore its potential further."
Wave Life Sciences plans to extend its RNA editing technology to Huntington’s disease, Duchenne muscular dystrophy, and obesity, conditions often associated with single-point mutations. Other companies, including Korro Bio, ProQr Therapeutics, and Shape Therapeutics, are also using ADAR enzymes for RNA editing in diseases like Parkinson’s, heart disease, and neurological conditions, employing different guides, RNA types, and delivery mechanisms.
Ascidian Therapeutics is testing a candidate for ABCA4 retinopathy, where mutations in the large ABCA4 gene lead to varying disease severity. RNA editing offers a potential solution where standard gene replacement therapy is not feasible. The candidate entered clinical trials in January 2024 and received fast-track designation from the U.S. drug regulator.
Rznomics, a South Korean company, has received permission to conduct trials in the U.S. for its liver cancer treatment candidate, which regulates human telomerase reverse transcriptase, a protein affecting tumor formation. This candidate is already in phase I and II trials in South Korea.
Advantages of RNA Editing Over DNA Editing
RNA editing offers safety and flexibility advantages over DNA editing. DNA editing makes permanent changes to the genome, potentially leading to irreversible errors. RNA editing, however, makes temporary changes, allowing effects to fade over time. This reversibility allows doctors to halt therapy if problems arise, mitigating long-term risks.
CRISPR-Cas9 and other DNA editing tools require bacterial proteins for cutting, which can trigger immune reactions. RNA editing relies on ADAR enzymes, naturally occurring in the human body, reducing the risk of allergic reactions, particularly beneficial for patients needing repeated treatment or with immune sensitivities.
Challenges and Future Directions
A key challenge in RNA editing is specificity. ADARs can perform unintended adenosine-inosine changes, causing potential side effects. Scientists are working to improve gRNA accuracy by shielding non-targeted mRNA parts.
The transient nature of RNA editing, while a strength, necessitates repeated treatments to sustain therapeutic effects. Current delivery methods for the gRNA-ADAR complex use lipid nanoparticles, similar to mRNA vaccines, and adeno-associated virus (AAV) vectors, both with limited carrying capacity for large molecules.
Despite these challenges, the field is rapidly advancing. There are at least 11 biotechnology companies developing RNA editing methods for various diseases, attracting interest from major pharmaceutical firms like Eli Lilly, Roche, and Novo Nordisk. As research and clinical trials progress, RNA editing is poised to become a crucial tool in clinical practice.
