Science & Health

US Experts Say Three-Parent Babies Are OK, Just No Girls

US Experts Say Three-Parent Babies Are OK -- Just No Girls

A controversial fertility treatment requiring three genetic parents has been approved by an FDA-appointed expert panel. This means the therapy, which eliminates rare mitochondrial diseases, could soon be legal in the US. But on the recommendation of the panel, it won’t be available to girls.

After months of work, a panel from the US National Academy of Medicine (formerly the Institute of Medicine) has released its much anticipated report on mitochondrial replacement techniques (MRT). The panel, put together last year at the request of the FDA, was asked to consider the ethical, social and policy issues raised by the prospect of three-parent IVF.

In its final report, the panel said that “it is ethically permissible to conduct clinical investigations of MRT”, but to ensure that clinical investigations are performed ethically, “certain conditions and principles” must be met. The FDA will now likely approve the practice, while making sure to set up the proper regulatory protocols.

“This will be an amazing breakthrough, benefiting patients who otherwise could not have healthy, genetically related children,” noted Dr Owen Davis, president of the American Society for Reproductive Medicine.

Defects to mitochondrial DNA affect about 1 in every 5000 births and can lead to severe or even fatal medical conditions, including seizures, developmental delays, vision loss and weakness and fatigue. One way to overcome these mitochondrial problems is to take two eggs, one from the mother and one from a donor. The nucleus of the donor egg is removed, leaving the mitochondria intact, and it’s then replaced by the mother’s nucleus. The resulting embryo has the donor’s healthy mitochondria, hence the term “three-parent baby”(though the genetic contribution from the donor is minuscule).

One major stipulation made by the panel is that scientists can only use MRT to create male embryos. At least for now. The fear is that “dangerous” mutations might be passed down to future generations. Germline changes to mitochondrial DNA are not heritable via the male line, which is why girls are being excluded (actually, males can pass the trait down one generation, but no further). This policy will likely change once scientists can prove that these alterations are safe.

As noted in New Scientist, researchers in the UK have already criticised the sons-only recommendation; last year, the British parliament approved MRT without this restriction. The committee is probably being overcautious; by the time these babies reach their reproductive years, genetic technologies will be considerably more advanced.

The panel said that initial investigations of MRT should be considered by the FDA only if certain conditions are met, including tests to establish safety (that is, in vitro modelling, animal testing and testing on human embryos), and by ensuring that the technique is “limited to women who are at risk of transmitting a severe mitochondrial genetic disease that could lead to a child’s early death or substantial impairment”. The panel also recommended that nonviable human embryos be used in preclinical research when possible.

The panel also said that US federal funds will probably not be used for these experiments, citing ethical concerns as it pertains to the destruction of human embryos.

“While the creation of human embryos for research is not prohibited under federal law in the United States (although some states are more restrictive), neither FDA nor any other agency of the U.S. Department of Health and Human Services can financially support such research where embryos are destroyed, discarded, or subjected to risks with no prospect of medical benefit for the embryo,” wrote the committee in its report.

The FDA now has a decision to make, though it’s not clear when that will happen. Though far from perfect, and even a bit paranoid, the recommendations made by the Institute of Medicine are providing a way for US researchers to move forward. The lives of future children depend on this research.

[NBC, New Scientist]

Top image: Shutterstock.


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