In a first, scientists edit genes inside a man’s body to try to cure a disease. What’s next?

Scientists have attempted to cure a patient with a rare genetic disorder by rewriting the DNA inside his body, in a first-of-its-kind therapy they hope could one day be applied to numerous other conditions including hemophilia and sickle cell disease.

The procedure, which took place on Monday at the University of California at San Francisco's Benioff Children's Hospital in Oakland, Calif., involved sending what the Associated Press described as “billions of copies of a corrective gene and a genetic tool to cut his DNA in a precise spot” into the patient's body. These edits are designed to enable the patient, 44-year-old Brian Madeux, to produce an enzyme that would counteract a metabolic disease he suffers from known as Hunter syndrome.