Breakthrough in Gene Editing for Rare Disorders

A nine-month-old boy became the first known recipient of a custom gene-editing treatment. He suffers from CPS1 deficiency, a rare genetic disorder that leads to toxic ammonia levels in the blood. This treatment was developed by researchers at the University of Pennsylvania and the Children’s Hospital of Philadelphia, utilising an advanced technique known as base editing, a refined version of the CRISPR-Cas9 technology.

About CRISPR Technology

CRISPR stands for clustered regularly interspaced short palindromic repeats. It is a natural immune system found in bacteria that protects against viruses. When a virus attacks, bacteria capture a piece of the virus’s DNA and integrate it into their own genome. This allows them to remember and combat future infections. The CRISPR system uses guide RNA and the Cas9 enzyme to cut and eliminate viral DNA.

The Evolution of Gene Editing

The CRISPR-Cas9 tool was developed in 2012 by scientists Jennifer Doudna and Emmanuelle Charpentier. They replicated the bacterial immune mechanism to create a gene-editing tool that allows precise modifications to DNA. This technology earned them the Nobel Prize in Chemistry in 2020. CRISPR-Cas9 can identify and cut out abnormal DNA sequences responsible for genetic disorders.

Mechanism of CRISPR-Cas9

CRISPR-Cas9 functions like a computer’s “cut-copy-paste” feature. It identifies abnormal DNA sequences and creates a guide RNA attached to the Cas9 enzyme. This guide RNA locates the faulty DNA, allowing Cas9 to cut it. Once cut, the DNA strands can repair themselves, but scientists provide a correct DNA sequence to ensure proper healing.

Introduction to Base Editing

Base editing is a newer method that allows precise single-base conversions without creating double-strand breaks. It combines a Cas9 enzyme with a base-modifying enzyme, enabling targeted corrections of DNA mispairings. For KJ, scientists identified the specific base causing his condition and programmed the base editing tool to correct it.

Challenges in Widespread Adoption

Despite the success, base editing faces hurdles. High costs make treatments inaccessible to many. KJ’s treatment was a one-off solution tailored to his unique genetic disorder, which complicates scalability for broader use. Regulatory challenges also hinder the development and approval of such personalised therapies.