They then injected the CRISPR/AAV8 combination into a mouse's bloodstream to reach every muscle and found some correction of muscles throughout the body, including in the heart -- a major victory because heart failure is often the cause of death for Duchenne patients.

"There is still a significant amount of work to do to translate this to a human therapy and demonstrate safety," said lead author Charles Gersbach, associate professor of biomedical engineering at the Duke University. "But these results coming from our first experiments are very exciting."

In a second study, Chengzu Long and colleagues from the University of Texas used adeno-associated virus-9 (AAV9), which displays a high affinity for muscle, to deliver the CRISPR editing components into the abdomen, into muscles, or into the backs of eyes of newly born mice.

While each delivery method had its unique benefits and improved muscle function, they found that dystrophin protein levels were highest when the treatment was injected directly into muscles.

A third study by scientists at the Harvard University also used CRISPR and AAV9 to edit out one of the dysfunctional exons of the dystrophin gene, finding similar beneficial restoration of muscle functioning.

"Recent discussion about using CRISPR to correct genetic mutations in human embryos has rightfully generated considerable concern regarding the ethical implications of such an approach," said Gersbach.

"But using CRISPR to correct genetic mutations in the affected tissues of sick patients is not under debate. These studies show a path where that's possible, but there's still a considerable amount of work to do," he said.