Doctors in Newcastle have been granted permission to use the three-person baby fertility technique to prevent incurable genetic diseases being inherited by children.
What is mitochondrial replacement therapy (MRT)?
MRT is an experimental treatment that was made legal in Britain in 2015. It aims to prevent serious disorders from being passed to children, caused by mutations in mitochondria, tiny structures that provide energy inside cells. Children inherit all their mitochondria from their mothers. MRT uses healthy donor mitochondria to replace the faulty ones. The child therefore has the usual 46 chromosomes from its parents, plus additional DNA from the donor's mitochondria. To perform MRT doctors pluck the nucleus from the mother’s egg, place it in a healthy donor egg, then fertilise it. Another similar approach uses fertilised eggs.
The IVF method, in which babies are created with DNA from three people – the mother, father and a female donor – was approved as safe for clinical use in December.
The fertility regulator, the Human Fertilisation and Embryology Authority (HFEA), issued its first licence for the procedure to the Newcastle Fertility Centre on Thursday.
“It’s great news,” Mary Herbert, professor of reproductive biology at the clinic, told the Guardian. “We hope to offer treatment to the first patients from the summer.”
The licence was awarded after an HFEA committee agreed that the Newcastle centre had the appropriate expertise, staff and equipment to offer what is known as mitochondrial replacement therapy (MRT).
The doctors will now identify patients who could potentially benefit from the therapy and apply for separate licences to perform the treatment. The Newcastle lab is in the middle of a major refurbishment, but is due to be back in operation by the summer.
If the clinic gets the green light to treat patients, the first babies in Britain to carry DNA from a mother, father and a donor woman could be born early next year.
Prof Herbert said many years of research had led to the development of MRT as a treatment to reduce the risk of mothers transmitting disease to their children.
“It’s a great testament to the regulatory system here in the UK that research innovation can be applied in treatment to help families affected by these devastating diseases,” she said.
The technique was developed to prevent women from passing on faulty DNA in their mitochondria, the power-generating structures that sit inside cells. A single cell can hold hundreds or thousands of mitochondria which are passed on solely from mother to child.
Harmful mutations in mitochondrial DNA can have a devastating impact on children who inherit them. Because the mutations affect how much energy is available for cells, they can cause progressive failure in the most energy-hungry tissues, including the heart, brain and muscles. About one in 10,000 newborns are affected by mitochondrial disease.
Doug Turnbull, director of the Wellcome Centre for Mitochondrial Research at Newcastle University, said: “I am delighted for patients as this will allow women with mitochondria DNA mutations the opportunity for more reproductive choice.”
“Mitochondria diseases can be devastating for families affected and this is a momentous day for patients who have tirelessly campaigned for this decision,” he added.
MRT aims to prevent the mutated mitochondria in an affected woman from being passed on to her children. It works by creating an IVF embryo that replaces the faulty mitochondria with healthy ones from a donor. All the rest of the DNA in the embryo, which influence looks and behaviour, come from the mother and father as usual. The donor mitochondria hold about 37 genes, equivalent to 0.2% of the embryo’s whole genome.
Women who carry faulty mitochondria already have some options if they want to have children. Beyond adoption, they can have IVF with donor eggs. Or they can have IVF with their own eggs and have the embryos screened for genetic faults before they are implanted. But some some women have such a large amount of mutated mitochondria that all of their embryos will inherit the faults.
Turnbull believes the Newcastle clinic could treat about 25 women a year. But MRT is not without its own risks. Studies have found that small amounts of mutated DNA are often still present in MRT embryos and this can sometimes bounce back to disease-causing levels.
Sally Cheshire, the chair of the HFEA, said: “This significant decision represents the culmination of many years of hard work by researchers, clinical experts, and regulators, who collectively paved the way for parliament to change the law in 2015 to permit the use of such techniques.
“Patients will now be able to apply individually to the HFEA to undergo mitochondrial donation treatment at Newcastle, which will be life-changing for them, as they seek to avoid passing on serious genetic diseases to future generations.”
Nicola Blackwood, the public health and innovation minister, said: “Serious mitochondrial diseases cause immense suffering to families and that’s why we need to use new ground-breaking procedures to reduce the risk of these diseases being passed on.
“The team at Newcastle are amongst the very best in the world and their work will help families across the UK and the world.”