Next Frontier in Gene Therapy - RNA Editing.

imhotep

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  • Mar 29, 2017
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    The US FDA has just approved the first-ever clinical trial that uses CRISPR-Cas13 RNA editing. Its aim is to treat an eye disease called wet age-related macular degeneration that causes vision loss in millions of older people worldwide.

    This trial marks a new frontier in gene therapy—the process of treating or curing medical conditions by changing a person's genes. What makes it special is the fact the therapy targets RNA, instead of DNA.

    RNA editing is emerging as a promising and potentially safer alternative to therapies that modify an individual’s DNA. Unlike DNA editing, which can cause permanent changes and unintended effects, RNA editing results in temporary modifications. Basically it alters the steps that happen after the RNA molecule "reads" the DNA instructions.
    This makes the approach potentially safer, as any genetic changes can be stopped or reversed because cells continually produce new RNA copies.

    This means it can be used to produce more targeted results by, for example, only altering how one specific protein is made. This also makes it a potentially safer option over DNA editing, with fewer unintended effects on other cells.

    RNA editing also has an advantage where you can potentially control or reverse the therapy, providing a level of control DNA editing can't provide.

    Age-related macular degeneration or AMD affects more than 200 million people worldwide and is predicted to grow to 300 million by 2040.
    As the name suggests, age plays a role—it almost exclusively affects people older than 55 years. AMD affects the health of the macula, the central part of the retina, which processes what we see. It's a leading cause of irreversible blindness around the world.

    Wet AMD occurs when there is a build-up of fluid and new, leaky blood vessels underneath the macula, causing rapid and severe impact to a person's central vision. Currently, it's treated with regular drug injections into the eye to control the growth of the leaky blood vessels. The drugs block VEGF, or vascular endothelial growth factor, a molecule that tells our bodies to make new blood vessels.

    This is where RNA editing comes in. In the lab, scientists have proven that the delivery of the RNA editing therapy via a safe, engineered virus allowed for an effective reduction of VEGF levels to stop new blood vessel growth in the eye through a one-off injection. For treating wet AMD, it would mean no more monthly needles.

    The FDA-approved clinical trial will now assess the safety of RNA editing therapy for wet AMD. It's also the first-ever clinical stage trial for a CRISPR-Cas13 RNA editing therapy, marking a significant milestone for the field of research.