CRISPR-Cas9 Gene Editing Clinical Trial Treating Cases Of Inherited Blindness

Context

CRISPR-Cas9 (a human gene editing tool) was used to treat people with a rare form of inherited or congenital blindness.

Published In: The New England Journal of Medicine
The Study:
The Clinical trial was named BRILLIANCE with 14 participants (12 adults and two children).
- They suffered from a rare form of inherited blindness, known as Leber congenital amaurosis (LCA) and is the first to use gene therapy to treat children who had been born with a form of blindness.

Leber Congenital Amaurosis (LCA)

About: It is a family of congenital retinal dystrophies that results in severe vision loss at an early age (by the age of 1 year in most cases)
Symptoms: Nystagmus, sluggish or near-absent pupillary responses, severely decreased visual acuity, photophobia, and high hyperopia.
Incidence: It affects about one in 40,000 people.
Cause: This blindness is caused by a gene mutation that prevents a protein (CEP290), which is critical for sight from functioning properly.
Impact: LCA affects the function of the rods and cones in eyes.
- Rods and cones are photoreceptors in the retina cells in the eye that convert light into images.
- Rods are better at seeing black and white, enhancing night vision. And cones are better at absorbing color.
Prevention: Genetic testing before pregnancy or prenatal testing can identify patients at risk of passing this condition on to offspring.

Test: The study tested how well participants could see colored lights, navigate a small maze in varying amounts of light, and read from a chart after receiving the treatment.
Treatment: Participants in the study received a single dose of a CRISPR gene therapy called EDIT-101.
- The treatment cuts out the mutation in CEP290 and inserts a healthy strand of DNA back into the gene which restores normal function of the protein CEP290, allowing the retina to detect light.
Findings: 11 out of 14 participants experienced improved vision overall with 6 participants having major improvements and could identify objects and letters on a chart.
- EDIT-101 caused no serious adverse side effects in participants. Some patients reported mild adverse effects which resolved quickly.

CRISPR-Cas9

It is a Gene Editing tool and is a precise way of altering DNA. It cuts out specific strands of DNA, and replaces them with new strands.
CRISPR: It is the DNA-targeting part of the system which consists of an RNA molecule, or ‘guide’, designed to bind to specific DNA bases through complementary base-pairing.
Cas9: It stands for CRISPR-associated protein 9, & is the nuclease part that cuts the DNA.
The CRISPR-Cas9 system: The technology was adapted from a naturally occurring genome editing system used by bacteria as an immune defense.
- It helps the organisms recognise and fight off similar viruses in the future by acting like an immune system.
Recognition: In 2020, Emmanuelle Charpentier and Jennifer A. Doudna were awarded the Nobel Prize in chemistry for discovering CRISPR-Cas9.
Application: Researchers use CRISPR to edit DNA precisely and can be used for various purposes
- Treating genetic diseases
- Creating drought-resistant plants
- Modifying food crops
- De-extinction projects.
Future Scope:
- As of now, only one CRISPR treatment has been approved for clinical use ie. Casgevy (a treatment for sickle-cell disease) available in the US, the UK, and the EU since December 2023.
Ongoing clinical trials: Other CRISPR therapies are being tested for HIV/AIDS, diabetes, cancer, cardiovascular diseases, and antibiotic resistance with more than 200 people been treated with experimental CRISPR technologies.

Also Read: Casgevy And Lyfgenia: CRISPR-Based Gene Therapies

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