Emails show the Chinese researcher behind the claim of gene-edited babies told a U.S. Nobel laureate about the experiment months before the news became public.
The revelation comes as scientists debate whether and how to alert troubling research, and the need for clearer guidelines.
Several U.S. researchers knew or strongly suspected He Jiankui was considering genetically editing embryos. He tried to alter the genes of twin girls to help them resist possible future infection with the AIDS virus.
Messages obtained by The Associated Press show He told Nobel winner Craig Mello of the University of Massachusetts last April of a pregnancy. Mello expressed disapproval and concern about health risks.
Mello remained an adviser to He’s biotech company for another eight months. The gene-editing work was not a company experiment.