Context

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

Crispr-Cas9 and Inherited 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.

• 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.

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Clustered Regularly Interspaced Short Palindromic Repeats (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.

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