In a much anticipated report on the ethics of Mitochondrial Replacement Therapy (MRT), a panel of U.S. experts said that the controversial technique, which has emerged as viable treatment for rare congenital diseases and was approved in the U.K. last year, was permissible “as long as significant conditions and principles are met.” However, the green light from the advisory panel is unlikely to translate into clinical application anytime soon as the omnibus fiscal 2016 budget bill passed by U.S. Congress last year prohibits the government from allowing genetic alteration of human embryos.

“In examining the ethical, social, and policy issues associated with mitochondrial replacement techniques, we concluded that the most germane issues could be avoided if the use of these techniques were restricted by certain conditions, rather than prohibiting them altogether,” Jeffrey Kahn, a bioethicist at Johns Hopkins ­University, who chaired the National Academies of Sciences, Engineering and Medicine committee, said, in a statement.

One such restriction the panel recommended is limiting the experimental procedures to male embryos, in order to prevent potential “adverse and uncertain” consequences.

Human cells contain two types of DNA — the nuclear DNA that’s found in the nucleus, and the mitochondrial DNA, which is present in the cells’ energy-producing mitochondria. Unlike the nuclear DNA, mitochondrial DNA is inherited solely from the mother.

Defects to mitochondrial DNA affect about 1 in every 5,000 births and can lead to severe, and, in some cases, even fatal birth defects. MRT, the gene-therapy technique in question, involves replacing an embryo’s energy-producing mitochondria with healthy mitochondria from the egg of a second woman. The aim is to prevent the transmission of diseases caused by mutations in mitochondrial DNA.

A child born through this technique would have genes from three “parents” — one male and two females.

Opponents of MRT have not only raised ethical objections to the technique, by questioning the psychological and social implications of children with three genetic parents, they have also said that the technique should be avoided as the medical risks associated with changing mitochondrial DNA have yet to be fully understood.

Other critics have expressed concerns that, if the technique is approved, doctors will be free to start tinkering with genomes, opening the door to creation of so-called "designer babies."

“As such, human subject research utilizing genetic modification of embryos for the prevention of transmission of mitochondrial disease cannot be performed in the United States in FY 2016,” the U.S. Food and Drug Administration reportedly said Wednesday.