For the first time, scientists have attempted to edit a gene inside a patient's body to permanently change their DNA and cure a genetic disorder, according to Science.
Brian Madeux, a 44-year-old man with a metabolic disorder known as Hunter syndrome, received billions of copies of a corrective gene and a genetic tool to cut his DNA through an IV, according to the Associated Press, who first broke the news Wednesday.
This gene therapy is a modified form of CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeats, and is a gene-editing technology that allows scientists to edit an organism's DNA.
Here are five things to know about the first human trial.
1. Hunter syndrome is a genetic disease caused by a deficient or absent enzyme, which cells need to process certain sugars. Without the enzyme, sugars build up and cause developmental delays, organ problems, brain damage or premature death.
2. Mr. Madeux, who has a mild form of the disease that still led to more than two dozen operations, is part of a small clinical trial sponsored by Sangamo Therapeutics, a Richmond, Calif.-based biotech company.
3. The experimental treatment began Monday at the Oakland, Calif.-based UC San Francisco Benioff Children's Hospital.
4. Here is how the replacement gene is inserted.
- The gene-editing tool — a variation of CRISPR called zinc finger nucleases — is given through IV in the form of an altered virus that would not cause infection but is used to distribute cells.
- Copies of the virus cut the DNA helices of liver cells in a specific place near the promoter, or the DNA on-off switch.
- A protein called albumin is created from the virus' DNA instructions.
- This new gene directs the cell to make the deficient or absent enzyme.
5. While patients with Hunter syndrome often receive weekly infusions of the enzyme, the three-hour IV treatment would be a one-time event that will allow the liver to keep making the enzyme at a steady rate for years to come. It will take about one month for scientists to know whether or not the treatment was a success.