He Jiankui, the Chinese researcher who drew wide criticism when it emerged that he gene-edited several human babies, told an influential adviser about the work many months before it became public.
Though Nobel Prize winner and University of Massachusetts professor Craig Mello admonished He that the work was unethical, according to emails obtained by the Associated Press, Mello didn't go public with the revelation - and stayed on as an adviser to He's company until news broke about the controversial experiment.
He emailed Mello in April 2018, after he learned the pregnancy had succeeded, with the subject line "Success!"
In a reply, Mello raised ethical concerns about the work - and asked that He not discuss it with him further.
"I'm glad for you, but I'd rather not be kept in the loop on this," Mello wrote, according to the AP.
"You are risking the health of the child you are editing… I just don't see why you are doing this. I wish your patient the best of luck for a healthy pregnancy."
After He went public about the gene-edited babies, there was worldwide backlash from the scientific community. It emerged that he had forged an ethical review, his university fired him, and he is reportedly under the watch of armed guards.
In another email obtained by the AP, Mello seemed to anticipate that reaction, telling He that he was taking a "big risk" - and that he didn't want others to think that he approved of the work.
"I think you are taking a big risk and I do not want anyone to think that I approve of what you are doing," wrote Mello, who didn't reply to a request for comment from the AP.
"I'm sorry I cannot be more supportive of this effort, I know you mean well."