A British expert scientific panel gave its backing on Tuesday to potential new 3-way fertility treatments that would for the first time allow genetically modified embryos to be implanted into women.
The "three-parent" IVF techniques are designed to help families with particular genetic faults who want to avoid passing on incurable diseases to their children. They could be available for patients in two years, the scientists told reporters at a briefing in London.
Known as mitochondrial replacement or transfer, the methods are at the research stage in laboratories in Britain and the United States and have never yet been carried out in people anywhere in the world.
They are illegal in Britain for now, but the government said last year it was drawing up draft legislation which if passed into law would allow the treatments to go ahead if they proved safe and effective in clinical trials.
In the United States, the Food and Drug Administration (FDA)has also convened an expert committee to decide whether safety concerns raised by three-parent IVF are minimal enough to allow clinical trials in humans to begin.
Mitochondrial replacement involves intervening in the fertilization process to remove faulty mitochondrial DNA, which can cause inherited conditions such as fatal heart problems, liver failure, brain disorders, blindness and muscular dystrophy.
Mitochondria act as tiny energy-generating batteries inside cells, and around 1 in 6,000 babies around the world are born with serious mitochondrial disorders.
The potential treatment is also known as three-parent in vitro fertilization (IVF), because the offspring would have genes from a mother, a father and from a female donor.
Publishing its report on Monday, the British expert panel said the evidence it had seen so far "does not suggest that these techniques are unsafe" and does suggest they could be "potentially useful for a specific and defined group of patients".
"In the absence of any effective treatment, mitochondrial replacement therapies ... offer great hope to families affected by mitochondrial disorders," said Peter Braude, professor of obstetrics and gynecology at King's College London and a member of the panel.
Although some critics of mitochondrial transfer say it is akin to creating designer babies, replacing faulty mitochondria with healthy ones would not be genetic engineering in the usual understanding of the term. It would not make a child smarter, sportier, more attractive, or otherwise different from what his or her genome and environment would produce in the normal way.
Braude noted that "the implementation of any new medical treatment is never wholly without risk, and genetic alteration of disease is an important step for society that should not be taken lightly."
A national public consultation showed Britons broadly favor the idea, and the government has signaled it believes the treatments should be allowed to go ahead under strict regulation.
Because Britain is in the vanguard of this research, ethical concerns, political decisions and scientific advances here are closely watched around the world, particularly in the United States where scientists are also working on mitochondrial DNA transfer techniques.
One method, being developed at Britain's Newcastle University and known as pronuclear transfer, swaps DNA between two fertilized human eggs. Another, called maternal spindle transfer, swaps material between the mother's egg and a donor egg before fertilization.