He was scheduled to speak again at the conference on Thursday, but he left Hong Kong and through a spokesman sent a statement saying "I will remain in China, my home country, and cooperate fully with all inquiries about my work".
After a Chinese scientist announced this week the birth of twin girls whose DNA he had altered many months earlier when they were microscopic, single-cell embryos, condemnation of this previously secret experiment was swift and absolute.
He said Wednesday that all the couples involved in his study consented and directed people to his website, where he provided an example of the consent form, which described the study as an "AIDS vaccine development project". The Southern China Morning Post reported that more than 120 Chinese scientists condemned the experiment as "crazy" and "unethical".
He said there had been "another potential pregnancy" involving a second couple, but it is unclear whether that pregnancy is still ongoing.
But after He's presentation, conference Chairman David Baltimore said the research was not medically necessary, as there are other treatments for HIV.
The work by He is more controversial than other types of gene editing because it involves the CRISPR method, which means the babies would pass on their biological alterations to any future children, altering the human gene pool. More importantly, prospective parents anxious about more than one genetic marker, and who therefore might not have any "unaffected" embryos, could use gene editing to make changes at multiple places in their embryos' genomes. "And we did not hear answers to those questions". "We still need to understand the motivation for this". Many scientists condemned Jiankui's work, calling it unnecessary, given current preventative measures for HIV, smallpox, and cholera, and reckless, as gene-editing can cause off-target effects that are hard to predict and have significant developmental consequences.
The case prompted a heated debate among the scientific community, with many raising concerns over the lack of verified data and the risks of exposing healthy embryos to gene editing.
Daley spoke Wednesday at an global conference in Hong Kong, where the Chinese scientist, He Jiankui (HEH JEE-ahn-qway) of Shenzhen, also is scheduled to speak.
A Chinese scientist on Monday said he has created the world's first in a controversial medical procedure that threatens to shake the foundation of bioethics. "For this specific case, I feel proud, actually, I feel proudest".
Dr. Kiran Musunuru at the University of Pennsylvania called it "unconscionable.an experiment on human beings that is not morally or ethically defensible". Whether He violated reproductive medicine laws in China has been unclear; Qui contends that it did, but said, "the problem is, there's no penalty".
Musunuru is a gene editing expert and editor of a genetics journal.
China has always been considered on the forefront of gene-editing technology, bankrolling expensive research projects and boasting less regulation in the field than Western nations. Prof He also added that his university was unaware of his study. He said he would monitor the two newborns for the next 18 years and hoped they would support continued monitoring thereafter. "I knew where he was heading", Hurlbut said.
Feng Zhang of the Harvard-MIT Broad Institute said in a statement provided to MIT Technology Review that he was "in favor of a moratorium on implantation of edited embryos".
"I disagree with the notion of stepping out of the general consensus of the scientific community", Hurlbut said. To act on science before it's considered ready and safe is "going to create misunderstanding, discordance and distrust", he says.