Editing genes in human embryos could one day prevent some serious genetic disorders from being passed down from parents to their children — but, for now, the technique is too risky to be used in embryos destined for implantation, according to a high-profile international commission. And even when the technology is mature, its use should initially be permitted in only a narrow set of circumstances, the panel says.

Due to the shock announcement in 2018 that a scientist had edited an embryo to make it resistant to HIV and then implanted it, a commission was formed and the recommendations, released in a report on 3 September, were produced by experts in ten countries. The document joins a wealth of reports compiled in recent years that have argued against using gene editing in the clinic until researchers are able to address safety worries, and the public has had a chance to comment on ethical and societal concerns.

Although genome-editing technologies such as CRISPR–Cas9 offer a fairly precise way to edit the genome, they have been shown to generate some unwanted changes to genes and can produce a range of different outcomes even among cells in the same embryo.

There is also a significant need for scientists need to develop better methods for thoroughly sequencing a human genome from single cells, so that an edited embryo can be screened in detail for unwanted genetic changes. As well as study the people born with edited genomes and their children, to understand the mental and physical health effects of the procedure for generations to come.

Although It could be years before researchers are able to iron out these difficulties, this commission is a good first step towards better understanding the role gene editing could play in our society.