Chinese Scientist Who Says He Edited Babies’ Genes Defends His Work

A Chinese scientist who claims to have created the world’s first genetically edited babies said at a conference on Wednesday that his actions were safe and ethical, and he asserted that he was proud of what he had done. But many other scientists seemed highly skeptical, with a conference organizer calling his actions irresponsible.

“For this specific case, I feel proud, actually,” the scientist, He Jiankui, said at an international conference on genome editing in Hong Kong.

Indeed, the only thing Dr. He apologized for was that news had “leaked unexpectedly” that he had used the gene-editing technique Crispr to alter embryos and then implanted them in the womb of a woman who gave birth to twin girls this month.

Dr. He’s announcement of his embryo editing on Monday sent a thunderbolt through the scientific world. Scientists have been working assiduously to prevent just such a rogue use of the rapidly advancing technology for making changes in human DNA.

Scores of scientists — including many of the top-flight genetics experts gathered in Hong Kong for what they had expected to be a much less newsworthy conference — have called Dr. He’s conduct unethical. They say there are serious unanswered questions about the safety of embryo editing and a need to make sure that such research is conducted in a transparent, monitored way so the technology isn’t misused.

And Dr. He’s presentation Wednesday afternoon did not seem to mollify many of his colleagues’ concerns.

Immediately after his presentation, David Baltimore, a Nobel laureate who led the conference’s organizing committee, told the audience that what Dr. He had done “would still be considered irresponsible.”

Dr. Baltimore added, “I don’t think it has been a transparent process. We only found out about it after it happened, and after the children were even born. I personally don’t think it was medically necessary.”

Robin Lovell-Badge, a professor of genetics and embryology at the Francis Crick Institute in London who moderated the session, asked a question that he said was on many attendees’ minds.

“Why so much secrecy around this, particularly when you know the general feeling around the scientific community is we shouldn’t go ahead yet?” Dr. Lovell-Badge asked. “You know the accusation now is that you’ve broken the law. If you had involved the Chinese authorities, they might have said you can’t do it.”

When Dr. He, 34, walked onstage in an open-collar shirt carrying a tan briefcase, it was clear this would be no ordinary conference presentation. Although his appearance had been previously scheduled, Dr. Lovell-Badge said Dr. He had earlier “sent me the slides he was going to show in this presentation and it didn’t include anything that he is going to talk about today.”

Facing a packed auditorium of scientists and members of the media, Dr. He also acknowledged that he had not made his university in China aware of the research he was doing.

But he asserted that he had not been overly secretive about his work, saying that he had presented preliminary aspects of it at conferences and consulted with scientists in the United States and elsewhere. He said he had submitted his research to a scientific journal for review and had not expected to be presenting it at this conference.

And he insisted that the parents of the twins and seven other couples who had participated in his research were fully informed of the risks involved, and that they understood what was being done to their embryos.

“The parents were informed of the implication of this,” Dr. He said. “We reminded them of the option to leave the trial without implantation, or to choose the embryos. The couple elected to implant these embryos to start a two-embryo pregnancy.”

Showing a series of slides, he quickly described what he said was three years of work involving mice, monkeys and then human embryos. He used the editing technique, Crispr-Cas9, to disable a gene, called CCR₅, which creates a protein that makes it possible for H.I.V., the virus that causes AIDS, to infect people’s cells.

Dr. He said that with the help of an H.I.V./AIDS organization in China, he recruited eight couples in which the man had H.I.V. and the woman did not. One couple dropped out and another achieved a “chemical pregnancy,” a pregnancy which fails soon after the embryo is implanted in the womb.

After editing the CCR₅ genes, he said he used in vitro fertilization to create embryos that were resistant to H.I.V. The goal, he said, was to engineer babies who would not be vulnerable to H.I.V. infection.

Many scientists have noted that there are other, simpler ways to protect newborn babies of an infected parent, especially an infected father, from getting H.I.V. Embryo editing should be used only to prevent or treat dire medical conditions that cannot be addressed in any other way, they said.

But Dr. He suggested that the parents of the twins, especially the H.I.V.-positive father, saw the procedure as a way to recapture their reason for living.

“I feel proudest, because they had lost hope for life,” Dr. He said. “But with this protection, he sent a message saying he will work hard, earn money, and take care of his two daughters and his wife for this life.”

Scientists also objected to indications that Dr. He had not fully informed his colleagues, his university or the parents about what exactly he was doing. For example, while the consent form he gave to potential parents mentioned gene editing in the text, it initially describes the research as an “AIDS vaccine development project.”

Dr. He appears not to have sought approval from Chinese regulators, and he waited months to list his research in a Chinese clinical trial registry, not doing so until early November.

“Science is open, science is collaborative and communicative,” Feng Zhang, one of the inventors of the Crispr-Cas9 system and a core member of the MIT Broad Institute, said after Dr. He’s presentation. “What he has done was not transparent. It was against the community’s consent and it does not represent science.”

In addition, The Associated Press reported that Dr. He’s lab allowed some of the medical staff assisting with the project to believe that they were involved in conventional IVF efforts that also included mapping genomes — nothing that involved editing embryos.

While Dr. He said the twins were “born normally and healthy,” other scientists questioned how healthy they would turn out to be. Dr. He said that in one of the twins, both copies of the CCR₅ gene were disabled, but that in the other twin, only one copy was.

That suggests that the twin with one disabled copy is still vulnerable to H.I.V. infection, scientists said. And Maria Jasin, a developmental biologist at the Memorial Sloan Kettering Cancer Center, pointed out to Dr. He that family dynamics could be affected “with the two girls being different, and this being something of an enhancement, not a disease correction.”

Dr. He said the parents were fully informed and that they decided to implant both embryos. He said the mother declined to have amniocentesis to check for genetic abnormalities during the pregnancy.

He said he planned to “monitor the twins’ health for the next 18 years, with the hope they will consent as adults for continued monitoring and support.” He referred to the girls by the names Lulu and Nana.

Dr. He said he initially paid for the research himself, then later from his university funding. He said he covered his patients’ medical expenses personally, and that neither of the two genomics companies he founded had paid for anything.

The birth of gene-edited children is alarming for both practical and theoretical reasons. First and foremost are safety concerns.

Most earlier efforts to edit embryos in a laboratory dish have resulted in some unintended effects, like off-target mutations that can occur in other genes, or mosaicism, in which the altered gene appears in some cells but not others. Scientists do not know the consequences of such effects.

Dr. He said he worked to minimize off-target effects and ultimately did not detect any after birth. He said he would continue to do blood tests and analyze for mosaicism or off-target mutations.

Another concern is that while editing of genes in most human cells to, for example, fix a disease-causing mutation affects only the person whose genes are edited, embryo editing — also called germline engineering — makes changes that are passed on to subsequent generations.

Then there is the concern that editing could be used to create babies with superior skills or desired physical features, changes that are not in the same league of importance as curing devastating genetic diseases and could have unpredictable social effects if such techniques became common.

Several countries, including the United States, have made it illegal to deliberately alter human embryos. It is not against the law in China, but is opposed by many researchers and institutions there.

A group of 122 Chinese scientists has issued a statement calling what Dr. He did “crazy.” His university, Southern University of Science and Technology in the city of Shenzhen, said in a statement that it was “deeply shocked” and believes that Dr. He “seriously violated academic ethics and codes of conduct.” The university said it would investigate the actions of Dr. He, who has been on unpaid leave since February.

Xu Nanping, China’s vice-minister of science and technology, said Tuesday that the Chinese government had issued regulations in 2003 that permitted gene-editing experiments on embryos for research purposes, but only if they remain viable no more than 14 days, according to the state broadcaster China Central Television. If the Chinese authorities confirm that the babies were born, that would be in violation of current regulations, Mr. Xu said.

As recently as last year, Dr. He wrote in a blog post that Crispr was a new technology that required “more in-depth research and understanding.” Performing gene-editing on humans without addressing the safety risks “is extremely irresponsible, both from the point of view of science and social ethics,” he wrote.