Experts from seven countries called Wednesday for a moratorium on the kind of genetic manipulation -- known as germline editing -- used last year to permanently modify the genome of twin girls in Shenzhen, China.
Chinese scientist He Jiankui's announcement in November that he had altered their DNA using molecular scissors -- ostensibly to prevent them from contracting HIV -- provoked a global backlash from scientists saying the untested procedure was unethical and potentially dangerous.
"We call for a global moratorium on all clinical uses of human germline editing -- that is, changing the heritable DNA in sperm, eggs or embryos to make genetically modified children," the researchers said in a joint statement, published in the scientific journal Nature.
"The introduction of genetic modifications into future generations could have permanent and possibly harmful effects on the species," they warned.
About 30 nations currently have legislation directly or indirectly barring all clinical use of germline editing.
CRISPR-Cas9 technology -- which combines DNA strands with an enzyme to achieve ultra-precise genome editing -- can be used to correct genetic defects in a singe organism, plant or animal.
But it can also be used to introduce desirable traits that can be passed on to future generations, a science-fiction scenario that has firmly, and quite suddenly, entered the realm of the possible.
Fired from his university, He is under police investigation and has been ordered to halt his work. Last month, the Chinese government unveiled new rules to supervise biotech research, including stiff sanctions for scientists who break the rules.
"By 'global moratorium', we do not mean a permanent ban," the authors, led by president and founding director of the Broad Institute of MIT and Harvard, Eric Lander, said.
"Rather, we call for the establishment of an international framework in which nations -- while retaining the right to make their own decisions -- voluntarily commit to not approve any use of clinical germline editing unless certain conditions are met."
Such a temporary ban would not, for example, apply to pure research.
The 18 signatories distinguished between "genetic correction" aimed, for example, at modifying rare genetic mutations linked to a specific disease, and "genetic enhancement" designed to boost intelligence, memory, or muscle performance.