The doctor who created a genetically modified “three-parent baby” has been reprimanded by the Food and Drug Administration for aggressively marketing the unapproved experimental procedure.

John Zhang, CEO of the New Hope Fertility Center in New York, famously combined the DNA of three people to help a mother who was a carrier for a genetic disease conceive an apparently healthy baby boy last year. Now, Zhang and his company are marketing the pricy procedure as the “first proven treatment for certain genetic disorders and a successful solution to age-related infertility.”

However, the FDA does not allow clinical research in people that would involve genetically modifying an embryo. And because Zhang’s technique and the one child it produced are both still in their infancy, we don’t know how well the treatment really works, or if it comes with any unforeseen consequences. On Friday, the FDA posted a letter to Zhang online, informing him that marketing the procedure is illegal, since the FDA hasn’t given him permission to test it in people. The agency asked him to correct his violations, and respond in writing.

“It’s a Catch 22.”

Zhang sought permission to conduct clinical research in April 2016, the FDA’s letter says. But the FDA is legally barred from even considering requests to modify the genes of an embryo that could then be inherited. “It’s a Catch 22,” says Leigh Turner, a bioethicist at the University of Minnesota who first brought the FDA’s letter to public attention.

Zhang promised that until the FDA gave him permission, his company Darwin Life wouldn’t generate any more modified embryos in the US, the letter says. However, he, Darwin Life, and New Hope Fertility Center continue to market the procedure — calling it HER IVF, or Human Egg Rejuvenation In Vitro Fertilization. The Darwin Life website says that HER IVF is “designed to reverse the effects of age on human oocytes and repair certain cellular defects.” The procedure will cost about $100,000, MIT Technology Review’s Emily Mullin reported in June 2017.

But without clinical trials, it’s impossible to say what the risks and the benefits of the procedure truly are for people trying to avoid passing a genetic disease to their children. Or whether the technique is even capable of “rejuvenating” an older woman’s egg “by replacing its ‘batteries,’” as Zhang’s blog claims.

“You have individuals who are desperate to have a child, who are concerned about mitochondrial disease, and so are vulnerable to these aggressive marketing tactics,” Turner says. “This is an area where I think there’s something to be said about being cautious, being careful, being prudent, and not just jumping out there into the market place.” Zhang, New Hope, and Darwin Life were unavailable for comment. (Zhang responded via email he might be available to comment later in the week, and the story will be updated at that time.)

“There’s something to be said about being cautious, being careful, being prudent.”

Zhang isn’t the first to combine the DNA of three individuals in a single embryo, but long term studies of the so-called three-parent babies of the 1990s are limited. He is the first to use a technique called nuclear transfer, which takes advantage of the fact that there are two different kinds of DNA in human cells. The bulk of the mother’s genome is tangled in the egg’s nucleus, but separate strands of DNA floating in the egg cell build the body’s energy generators, the mitochondria.

Mutations in mitochondrial DNA are passed down by the mother, and can cause life-threatening and incurable diseases in her child. By combining the nuclear DNA of the mother with the unmutated mitochondrial DNA from an egg donor, it might be possible to prevent a child from inheriting the disease.

Zhang and his colleagues modified a human embryo to try and bypass a mutation in the mother’s mitochondria. In New York, the team injected the mother’s nuclear genome into the hollowed egg from a donor. After fertilizing the egg, they then shipped the embryo to Mexico to implant in the mother’s uterus. In its letter, the FDA informed Zhang that such embryo exports are not permitted.

Without tracking the child’s health through adulthood, it’s impossible to say whether the procedure is safe or effective

In April 2017, Zhang reported that the baby was still healthy seven months after it was born. But in an editorial published alongside the study, experts noted that without tracking the child’s health through adulthood, it’s impossible to say whether the procedure is safe or effective in the long term. Follow up studies will be tricky, because the child’s parents have said that they don’t want their child’s genes tested for the mutation unless it’s absolutely necessary.

The UK has approved a similar mitochondrial replacement technique, but only in attempts to prevent the child from inheriting a genetic disease. Last year experts recommended that mitochondrial replacement therapies also be allowed in the US to prevent genetic diseases, under very specific conditions. However, it currently remains banned.

“This is a biologically extreme and risky procedure,” Marcy Darnovsky, executive director of the Center for Genetics and Society, told MIT Technology Review. “If you’re talking about using these techniques for age-related infertility, that’s really moving the human experimentation to a very large scale.”