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". However, his work has not been verified. "Conducting direct human experiments can only be described as insane", the scientists said in their letter, a copy of which was posted by the Chinese news website the Paper.
It also emerged today that a group of leading scientists has declared that the world isn't ready for gene-edited babies, following Dr He's shock claims.
The Ministry of Science and Technology in Beijing has vowed to get to the bottom the claims, and health authorities in Guangdong province and Shenzhen - where He claimed to have conducted the experiment - have joined forces for an investigation. He said he had initially paid for the research himself, then later from his university funding.
Mathew Porteus, a pediatric stem cell scientist at Stanford University, said that in February, He told Porteus about his animal studies and an open trial in humans.
He explained that eight couples - comprised of HIV-positive fathers and HIV-negative mothers - had signed up voluntarily for the experiment; one couple later dropped out.
"This study has been submitted to a scientific journal for review", He said, but did not name the journal.
Dr. Kiran Musunuru of the University of Pennsylvania and Harvard University's George Church have questioned the decision to allow one of the copies to be used in pregnancy attempt, as the researchers new in advance that both copies of the intended gene had not been altered saying in this child nearly nothing will be gained in terms of protection exposing it to all of the unknown safety risks; and use of that embryo suggests main emphasis was on testing editing rather than avoiding disease.
But he apologised that his research "was leaked unexpectedly", and added: "The clinical trial was paused due to the current situation".
Other researchers at U.C.L.A., including neurology chairman S. Thomas Carmichael, are now conducting a clinical trial using the HIV drug Maraviroc to deprive stroke victims of CCR5, hoping it will boost their recovery.
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It works by using "molecular scissors" to alter a very specific strand of DNA - either cutting it out, replacing it or tweaking it.
He's claims has set off a firestorm of skepticism and criticism.
He's research has raised serious ethical questions around the transparency of gene editing and sparked calls for a globally binding code of conduct.
Even if editing worked perfectly, people without normal CCR5 genes face higher risks of getting certain other viruses, such as West Nile, and of dying from the flu.
Experts warned that editing human embryos can create unintended mutations in other areas - so-called "off-target effects" - which can have an impact through the lifetime.
The man at the center of the controversy, He Jiankui, presented unverified research in which he claims to have tweaked the genes of human embryos in order to make them resistant to HIV.
China's vice minister of science and technology, Xu Nanping has said that the government is opposing this project and said in a statement that this experiment on human embryos has "crossed the line of morality and ethics adhered to by the academic community and was shocking and unacceptable".
China allows in-vitro human embryonic stem cell research for a maximum period of 14 days, Mr Xu said.