A Chinese scientist who claims to have created the world's first genetically-edited babies said the trial had been paused, following an international outcry over the highly controversial procedure.
Professor He Jiankui told a packed Hong Kong medical conference that he had successfully altered the DNA of twin girls born to a HIV-positive father.
A total of eight volunteer couples - HIV-positive fathers and HIV-negative mothers - had signed up to the trial, with one dropping out before it was halted.
"I must apologise this result was leaked unexpectedly," said Prof He.
"The clinical trial was paused due to the current situation," he added.
The Chinese hospital linked to Prof He’s experiment denied its involvement.
Shenzhen Harmonicare Women and Children's Hospital said in a statement yesterday that it suspected the signature on a document approving the experiment, specifically its adherence to ethical standards, was falsified.
It has also asked police to investigate.
"We have always firmly opposed the development of genetic experiments that violate human ethics and morality," the hospital said on its website.
In interviews with Chinese media, Cheng Zhen, the general manager of the hospital, said the hospital had not partnered with Prof He, and that he had never even met the man before.
Scientists have warned that exposing healthy embryos and children to gene editing was irresponsible, while others denounced Prof He's experiment as premature and dangerous.
Chinese scientists and institutions have also criticised the experiment, with 100 scientists issuing a joint statement calling for better state legislation.
"It is a great blow to the global reputation and development of biomedical research in China," said the statement posted on the Twitter-like platform Weibo.
The university where Prof He worked has also distanced itself from the scientist's experiment.
"This research work was carried out by Professor He Jiankui outside of the school," the Southern University of Science and Technology said in a statement Monday.
He has been on unpaid leave since February and his research is a "serious violation of academic ethics and norms", it said.
Prof He told the Hong Kong conference that his study has been submitted to a scientific journal for review, without naming the journal.
Prof He, who said his work was self-funded, shrugged off concerns that the research was conducted in secrecy, explaining that he had engaged the scientific community over the past three years.
In videos posted online this week, Prof He said he used a gene-editing technology known as CRISPR-Cas9 to alter the embryonic genes of the twin girls born this month.
He said gene editing would help protect the girls from infection with HIV, the virus that causes AIDS.
The conference moderator, Robin Lovell-Badge, said the organisers were unaware of the story until it broke this week.
CRISPR-Cas9 is a technology that allows scientists to essentially cut and paste DNA, raising hope of genetic fixes for disease. However, there are concerns about safety and ethics.
The Chinese Society for Cell Biology in a statement yesterday strongly condemned any application of gene editing on human embryos for reproductive purposes and said that it was against the law and medical ethics of China.
More than 100 scientists, most in China, said in an open letter that the use of CRISPR-Cas9 technology to edit the genes of human embryos was dangerous and unjustified. "Pandora's box has been opened," they said.
Prof He's research focuses on genome sequencing technology, bioinformatics and genome editing, according to his biography on the conference's website.
He received his PhD at Rice University in Houston, Texas,and worked as a postdoctoral research fellow in Stephen Quake lab at Stanford University according to the site.
David Baltimore, President Emeritus; Robert Andrews Millikan Professor of Biology, spoke after Prof He's speech, saying it was irresponsible to have proceeded until safety issues were in order.
"I don't think it has been a transparent process. Only found out about it after it happened and the children were born," he said.
Prof He said his results could be used for millions with inherent diseases. He said he would monitor the two newborns for the next 18 years and hoped they would support continued monitoring thereafter.
