The editing of muscle cells in young beagles, bred to have Duchenne muscular dystrophy, to remove a key barrier to higher protein production could greatly further the treatment of the disease in humans. Scientists from the University of Texas Southwestern Medical Center found that within two months of the gene editing, the dogs were producing much greater levels of dystrophin, a protein which helps muscles avoid degradation over time, with levels climbing to as high as 92% of normal in the cardiac muscle.

Duchenne muscular dystrophy, largely occurring in males, causes muscles to weaken from childhood, often leading to an early death from heart or respiratory failure. There is currently no cure.

Viruses were engineered to act as delivery vehicles for the new technology, removing the virus’ own DNA in the process. CRISPR-Cas9 was then loaded onto the viruses, which cut out the DNA sequence preventing production of dystrophin in muscles.

While this technique has been used before in rodents and human cells in the lab, this is the first such test to prove this technology works in larger mammals. The study focused on protein-level restoration alone, rather than changes to the dog’s lives. However the report, published in Science, said no unintended changes to other areas of the genome were found, and the dogs did not become ill from the technique.

It is yet unknown how long an injection of the Cas9 enzyme would last in human Duchenne sufferers, though the scientists said they hope it is durable enough for a single dose. Should more treatments be required over time, different viral vehicles may have to be used, due to the body developing antibodies.