Editor's note: This story was updated at 11:52 a.m. to add information about an ethics committee investigation into the DNA-editing experiment.
For the first time, a scientist claims to have used a powerful new gene-editing technique to create genetically modified human babies.
"Two beautiful little Chinese girls name Lulu and Nana came crying into the world as healthy as any other babies a few weeks ago," He says in a video posted online. "The babies are home now with their mom Grace and their dad Mark."
He says his team performed "gene surgery" on embryos created from their parents' sperm and eggs to protect the children from the human immunodeficiency virus, HIV, which causes AIDS. The children's father is HIV-positive.
"When Lulu and Nana were just a single cell, this surgery removed a doorway through which HIV enter to infect people," He says in the video, one of several posted online to justify and explain the work.
Because the research has not yet been published in a scientific journal or carefully vetted by other scientists, many researchers and bioethicists remain cautious about the claim.
But, if true, many said the move would be historic, comparing it to the birth of Louise Brown, the first baby created through in-vitro fertilization, IVF.
"This event might be analogous to Louise Brown in 1978," wrote George Church, a prominent Harvard geneticist, in an email. "Both anecdotal — yet healthy baby girls can have an impact," Church wrote.
Meanwhile, He is now facing investigation by a local medical ethics board to see whether his experiment broke Chinese laws or regulations.
The university where He worked issued a statement that officials were "deeply shocked" by the experiment, which it stressed was conducted elsewhere. He, the statement says, has been on unpaid leave from the university.
Church and He are among hundreds of scientists gathering at the Second International Summit on Human Gene Editing in Hong Kong. The summit was organized try to reach a global consensus on whether and how it would be ethical to create genetically modified human beings with CRISPR.
The claims by He sparked immediate widespread criticism from attendees at the summit and elsewhere.
"This work is a break from the cautious and transparent approach of the global scientific community's application of CRISPR-Cas9 for human germline editing," Jennifer Doudna, a biochemist at the University of California, Berkeley, said in an interview. Doudna helped discover CRISPR and organize the summit.
"All of us that are here at this conference are struggling to figure out what was done and also whether the process was done properly. We just don't know yet," Doudna says.
But the claim "really reinforces the urgent need to confine the use of gene-editing in human embryos to settings where there's a clear unmet medical need and where there's no alternative viable approach," says Doudna. She doesn't think that is the case in this situation.
"If this was done to avoid HIV infection, there are alternative ways to prevent infection that are already effective," Doudna says, such as "washing" the sperm of infected sperm donors to eliminate HIV. "Why would you use this instead of an already established approach?"
For their research, He and his colleagues say they used CRISPR to make changes in one-day old embryos in a gene called CCR5. The CCR5 gene enables HIV to enter and infect immune system cells. Scientists have long searched for ways to block this pathway to protect people from HIV.
He and his team say they used CRISPR to edit 16 embryos, and implanted 11 edited embryos into the wombs of women to attempt to create a viable pregnancy before the twin pregnancy was achieved, according to the Associated Press, which first reported He's claims.
"No gene was changed except the one to prevent HIV infection," He says. The twins appear to be healthy, and underwent detailed genetic analysis. "This verified the gene surgery worked safely," He says.
Nevertheless, other scientists questioned whether the editing really worked, and argue that it is far too soon for the team to try the experiment.
"It is premature at this stage of technology," wrote Shoukhrat Mitalipov, a scientist at the Oregon Health & Science University in Portland, Ore. Mitalipov was the first scientist to report using CRISPR to successfully edit human embryos, but stopped far short of trying to use them to make babies.
Other experts agree.
"Although I appreciate the global threat posed by HIV, at this stage, the risks of editing embryos to knock out CCR5 seem to outweigh the potential benefits," wrote Feng Zhang, a CRISPR pioneer at MIT. Zhang noted that knocking out the CCR5 gene "will likely render a person much more susceptible for West Nile Virus."
CRISPR enables scientists to make very precise changes in DNA much more easily than ever before. As a result, it's revolutionizing scientific research and raising high hopes for major breakthroughs, including preventing and treating many diseases.
But making changes in human DNA that could be passed down for generations has long been considered off-limits. One reason is that a mistake could introduce a new disease that could be passed down for generations. Another is that it could open the door to "designer babies" — children that are modified for nonmedical reasons, such as to be taller, stronger or smarter.
"If it's true as reported, then it's an extremely premature and questionable experiment in creating genetically modified children," agrees Jeffrey Kahn, a bioethicist at Johns Hopkins Berman Institute of Bioethics attending the Hong Kong summit.
But the development of CRISPR has prompted some scientists to rethink that prohibition for medical purposes. And researchers around the world have been racing to determine how it could be done safely. Many scientists believe it is inevitable, but should be restricted to situations where no alternative is available.
"If true, this amounts to unethical and reckless experimentation on human beings, and a grave abuse of human rights," said Marcy Darnovsky, executive director of the Center for Genetics and Society, a genetic watchdog group.
"Throwing open the door to a society of genetic haves and have-nots undermines our chances for a fair and just future," Darnovsky says.
Chinese researcher He acknowledges his work could spark criticism, but defends the step. "I understand my work will be controversial," he says. "But I believe families need this technology. And I am willing to take the criticism for them."
DAVID GREENE, HOST:
A Chinese researcher is claiming to have created the world's first genetically edited human babies. According to the scientist, the genes of two twin girls have been modified to resist HIV infection. That's the virus that causes AIDS. This claim is highly controversial with some scientists denouncing this work as unethical human experimentation. NPR health correspondent Rob Stein joins us now to talk about this. Hi there, Rob.
ROB STEIN, BYLINE: Oh, hey there, David.
GREENE: All right. Let's start by who the scientist is. And how are we learning about this right now?
STEIN: Yes. So his name is He Jiankui, and he works at the Southern University of Science and Technology in Shenzhen, China. Right now he's at a meeting in Hong Kong. It's the International Summit on Human Gene Editing. And that's where he's making this extraordinary claim.
GREENE: What is the claim? What does he say he's actually done here?
STEIN: Yeah, so he says he's used a powerful new kind of genetic engineering - it's called CRISPR - to make changes in human embryos and then use those human embryos to try to make babies. And he even claims, as you said, that he was able to create a pair of twin girls. And they were born a few weeks ago from these genetically modified embryos. And their names are Lulu and Nana. They're supposedly healthy and back home with their parents, Mark and Grace.
GREENE: So how is the scientific community reacting to this moment?
STEIN: Yeah. Well, as you mentioned, this is extremely controversial.
STEIN: I mean, a lot of scientists - you know, they think this sort of thing - it may be OK someday to try to prevent a long list of really terrible diseases. But even advocates of editing human DNA like this are saying, look. This is just way too premature. And we're kind of getting ahead of ourselves here. I talked to, for example, Jennifer Doudna. She's one of the scientists from California who's credited with helping invent CRISPR, this gene-editing technique. And, you know, she's saying that there's a lot of concerns. And a big one is safety, I mean, for any kids that anybody tries to make this way. And so a lot more research is needed to make sure it is safe and it really works. And perhaps even more importantly, scientists say, look. We need a broad societal debate to figure out, like, you know, in what circumstances should we do this? And how should we proceed? And we're far from having that consensus on how to modify the human genetic blueprint this way.
GREENE: I mean, a really significant debate because, I mean, this is this is raising the question of, you know, so-called designer babies and opening the door to all sorts of stuff, right?
STEIN: That's right. This is the sort of thing that's long been considered taboo - you know, genetically modifying human beings in a way that could be passed down for generations. And the big fear, as I said, is safety. You know, if scientists make some kind of mistake, they could, you know, create a new disease that would then be passed down for generations. And, you know, it does open the door to this, you know, kind of scary scenario people call designer babies, where scientists don't do this, you know, for medical reasons but for other reasons - to make taller babies, stronger babies. And that could lead to this - you know, maybe some kind of super race of human beings considered to be genetically superior.
GREENE: But you did say that a lot of scientists think there might be a way to do this in an acceptable way someday in the future. So, I mean, what happens now with this Chinese scientist who says he's done this?
STEIN: Yeah. So the big thing right now is to validate, did he really do this?
STEIN: I mean, you know, this sort of thing usually comes out in a scientific journal after being carefully reviewed by other scientists. And this is, you know, a valid line of research that people have been pursuing for a while. But, you know, scientists really first want to know whether this is true. I mean, this would be an historic claim. Some people are comparing this to the birth of the, you know, first IVF baby, Louise Brown. So we need a lot more research to figure out whether this is true. And that this meeting in Hong Kong is going on right now - the purpose of this meeting is to really try to create a scientific consensus for when we should proceed with editing human DNA this way.
GREENE: NPR health correspondent Rob Stein. Rob, thanks.
STEIN: Oh, sure. Thanks to be - nice to be here, David. Transcript provided by NPR, Copyright NPR.