Dr. John Zang holding a baby. (Science.org)

(CNSNews.com) -- The Food and Drug Administration (FDA) has demanded a fertility doctor halt all marketing on an unapproved IVF experiment that creates a human embryo by combining DNA from three separate people.

In an Aug. 4 letter to John Zhang, the chief executive officer of Darwin Life and New Hope Fertility Center, the FDA reminded the fertility doctor that his request to run clinical trials on mitochondrial replacement technology (MRT) was denied because it would involve the “intentional creation of a genetically modified embryo.”

Congress, since December 2015, prohibits the FDA from reviewing any applications for clinical experiments that use genetically modified human embryos.

Additionally, creating a genetically modified human embryo is allowed only if federal funds are not used. But implanting a genetically modified human embryo within a human womb is against the law.

To get around this law, Zhang created three DNA embryos for a woman who carries the gene for a rare neurological disorder and brought them to Mexico, where he legally implanted them in the mother. The mother gave birth to a boy in April of 2016.

Zhang, who told CBS News that the three DNA embryos were “very revolutionary,” submitted an application to the FDA to conduct further experimentation with MRT.

The application was turned down, but the FDA’s August letter stated that, in his application, Zhang agreed that he would not use the three-parent embryo technique in the United States.

“Despite that commitment, you continue to market MRT to prevent the transmission of mitochondrial disease and to treat infertility,” the letter reads.

The letter then went on to list the multiple instances in which Dr. Zhang violated the FDA’s regulations, asking him to right his wrongs.

“This letter is not intended to be an all-inclusive list of violations. It is your responsibility to ensure full compliance with the FD&C Act and the PHS Act and their implementing regulations,” the letter concludes.

“We request that you notify this office, in writing, of the steps you have taken or will take to address the violation noted above and to prevent recurrence,” said the FDA.