Let’s start at the beginning. How did you come to focus on mitochondrial disease?
“My entire career – even back to my PhD – has focused on mitochondria and mitochondrial disease. I was first drawn to it as a junior doctor on a neurology ward, where I saw a patient whose muscles would break down during exercise due to a lack of energy. That link between energy and disease fascinated me, and it led me into mitochondrial research.
We started a small mitochondrial clinic in the 1980s. By the mid-90s, we were seeing a lot of patients, and it became clear how devastating the disease was for families. For me, there were three main priorities at the time: better diagnosis, improved treatments and preventing transmission.
I met a woman who had lost seven children to mitochondrial disease. Her story had a huge impact on me, and it really cemented the idea that prevention needed to be a research priority. That’s really how the whole idea around mitochondrial donation started.
Around the same time, we came across a 1983 study in mice where scientists had successfully transferred pronuclei between fertilised eggs to create mice with the nuclear DNA from the original mouse and the mitochondrial DNA from another mouse. The mice were healthy, and while it wasn’t done for mitochondrial disease, the technique had potential to prevent transmission of mitochondrial DNA disease.
We secured our first grant in the early 2000s and, in 2005, the Newcastle Fertility Centre received a HFEA (Human Fertilisation Embryology Authority) licence to begin research using surplus human eggs. By 2010, we’d shown that the technique could work in human embryos, and that was incredibly encouraging. But of course, at that time, it wasn’t legal to use it in treatment.
So from 2012 to 2015, alongside refining the science, we also worked to change the law – that in itself was almost a full-time job. It was stressful, and there was some opposition, but we had strong support too, especially from patients and, of course, The Lily Foundation. It was a real partnership between mitochondrial specialists, fertility experts and patients, and that collaboration made all the difference. In 2015, the law changed, and by 2017 the Newcastle Fertility Centre finally had a licence to begin offering the technique.”
What were some of the challenges after the law around mitochondrial donation changed?
“Even then, it wasn’t straightforward. Some of the women who’d helped us get the legislation through Parliament had hoped to be among the first to try the technique. Sadly, by the time it became legal, many were older; fertility declines with age, which made the treatment less viable. That was difficult, and it did slow progress.
We’ve since adapted the eligibility criteria to reflect this. But overall, what’s been remarkable is the support we’ve received. Yes, we had to fight for it, but doors were opened too and there was a real willingness to see it succeed.
We were fortunate to already have the NHS Highly Specialised Service for Rare Mitochondrial Disorders, which had been established in 2007. I approached the head of that service to ask whether they could help fund the treatment. While the NHS couldn’t pay for a first-in-human technique, we secured a grant from Wellcome to run a clinical trial for the first 25 births, with the NHS picking up the excess costs.
What stood out was how willing people were to help. The head of the Highly Specialised Services at the time understood the importance of this advance for patients with mitochondrial disease. And it meant there was no cost to the women involved, which was crucial. Without that, it simply wouldn’t have been possible.
Sometimes you push and sometimes the doors just open for you. I think there was a strong sense that this was something the UK could lead on, thanks to that law change. It’s been a very positive experience.”
There’s been talk about using this technique more widely. What’s your view?
“There’s been some suggestion that mitochondrial replacement therapy could be used to treat infertility more broadly. Personally, I don’t think there’s much evidence for that, and in the UK, it’s illegal to use the technique for anything other than preventing serious mitochondrial disease.
One of the great strengths of the UK’s approach has been its regulatory rigour. The approval process involved three years of scientific discussion, public consultation and parliamentary debate. We have one of the best IVF regulatory frameworks in the world, and I think that’s something to be proud of.
What we’re doing here is preventing disease – not designing babies. It’s a totally different concept. And interestingly, we got very few ethical questions when the papers were published last month. I think the debate was done back in 2015.”
What does all this mean to you, personally?
“People asked me that at the news conference. And honestly, my first feeling was relief. I’m a natural pessimist, so I never assumed success was guaranteed.
More importantly, it’s fantastic for the mito community. This whole debate has massively increased the profile of mitochondrial disease, which can only be a good thing in terms of treatment and awareness. The fact that we can offer what I believe is the best care for people with mitochondrial disease, it gives me an immense amount of satisfaction to be part of that. And now, for some families, there’s also the chance to have children that are directly related to them and break the chain of disease. That’s very rewarding.”
And finally, what’s next for mitochondrial research?
“We still need better treatments. Mitochondrial donation prevents transmission, but it doesn’t help those already living with the disease. That has to be our next big focus.
As I said, diagnosis has moved on hugely, and we’ve made incredible progress on prevention. But for me, treating those patients who’ve already got mitochondrial disease is absolutely fundamental.
Yes, we can manage symptoms – epilepsy, heart failure or diabetes – but that’s not enough. What we need is curative treatments. And that’s difficult, because mitochondrial disease isn’t just one condition: it’s a whole spectrum of disorders caused by different mutations. What works for one may not work for others.
Still, we’re getting closer. Clinical trials are happening, companies are investing, and a lot of people are devoting a lot of time to it. So yes, there’s a long way to go, and many challenges ahead, but that’s what research is about.”