Scientists have for the first time used gene-editing tools to correct genetic disorders, establishing proof of the concept that it may be possible to correct some congenital disorders either in the womb or after birth.

Two research groups — one in the US and the other in Switzerland — on Monday announced they have used the gene-editing tools to correct genetic disorders in laboratory mice, raising hopes for similar applications in humans.

Gerald Schwank and his colleagues at ETH Zurich used the CRISPR/Cas9 tool to alter a specific gene in mice and cure them of an enzyme deficiency associated with the genetic disorder called phenylketonuria.

Babies born with phenylketonuria need special diets to prevent them from accumulating the amino acid phenylalanine in the body. Excess phenylalanine can delay their mental and motor development.

At the University of Pennsylvania in the US, researchers have reduced the cholesterol levels in healthy mice treated in utero by targeting a gene that controls cholesterol. They have also applied prenatal gene editing to improve the liver function of mice genetically engineered with a mutation that causes a lethal liver disease.

The results of the studies were published on Monday in the journal Nature Medicine.

“This approach has great potential for application in humans,” Schwank, a professor at the Institute for Molecular Health Sciences at ETH, said in a media release.

But the researchers also caution that their findings only demonstrate a concept and any applications in humans would need to be preceded by more studies on animals and tests to determine safety and efficacy in humans.

The researchers used a virus as a vehicle to apply the gene-editing tools. Future studies will also aim to determine whether the use of virus has any adverse effects as well as seek alternative vehicles such as nanoparticles.

“Our ultimate goal is to translate the approach used in these proof-of-concept studies to treat severe diseases diagnosed early in pregnancy,” study co-leader William Peranteau at the Children’s Hospital of Philadelphia said in a media release. “We hope to broaden this strategy to intervene prenatally in congenital diseases that at present have no effective treatment for most patients.”