Gene therapy: changing the future for people with rare diseases

“It felt so far out of reach. For so long, it felt like an impossible dream,” says 20-year-old Remi Pereszczak. “It’s crazy to think that this is my life now.”

For Remi, the treatment he received as part of a clinical trial at Great Ormond Street Hospital (GOSH) changed everything. Before then, much of his childhood had been shaped and limited by immune deficiency disease.

Regular hospital visits, frequent treatment and daily pain were part of life with p47 chronic granulomatous disease (CGD). As Remi got older, the restrictions tightened. He couldn’t play outside, build friendships or live like other teenagers.

Today, things look very different. Since having gene therapy in 2024, Remi has finished his A-levels and started university. He has built relationships he once thought impossible.

“I feel like a normal person,” he says. “It’s a big change, a big step in my life.”

Rare genetic conditions may be individually uncommon, but it is estimated that together they affect hundreds of millions of people worldwide. Often emerging in childhood, they can shape every aspect of life – from school and friendships to a person’s independence.

Remi has p47 chronic granulomatous disease (CGD), a condition that weakens the immune system. People with CGD are therefore vulnerable to serious illness.

“CGD is a life-threatening disorder,” says Claire Booth, professor of paediatric immunology and gene therapy at Great Ormond Street Hospital, who led Remi’s care and the clinical trial he took part in. “Patients often have very limited treatment options.”

Historically, treatment has been difficult. Bone marrow transplants can offer a cure, but suitable donors are not always available and outcomes have not always been reliable. For many, the reality has been lifelong management rather than recovery.

Gene therapy is designed to treat disease by correcting the genetic problem, rather than managing symptoms. The benefits can be life-changing, offering long-term health improvements in place of frequent, short-term and less effective treatments.

In Remi’s case, doctors at GOSH used a type of gene therapy called ex vivo treatment. They took some of his blood stem cells – the cells that make the immune system – and corrected them in the lab using a modified virus to deliver the working gene. The corrected cells were then returned to his body, where they could begin rebuilding his immune system.

“If we can correct those [blood stem cells], the idea is that we’ll be able to give that patient a working immune system that will last them for the rest of their life,” says Claire.

The treatment that Remi received has been decades in the making. Early breakthroughs came from research into rare immune disorders, where researchers learned how to insert working genes into blood stem cells and make those changes last.

Adrian Thrasher was one of the key figures in that work. Over many years as Professor of Paediatric Immunology at University College London and GOSH, he helped pioneer gene therapy for inherited immune disorders and bring it into clinical use. He and Bobby Gaspar were part of the team at GOSH that treated the first child in the UK with gene therapy in 2001. 

Adrian’s work was supported by Wellcome from the early 1990s onwards, helping sustain the long-term research needed to develop these approaches. His first Wellcome fellowship supported the development of gene therapy for p47 CGD – Remi’s condition. 

As Claire says, simply showing that this could be done at all was crucial: “That was really the first step. Being able to actually put a gene in a person’s DNA and that gene worked.”

This breakthrough laid the foundations for the gene therapies used today, including treatments like the one that changed Remi’s life.

For Remi, the shift from research to treatment is life-changing. He was the first patient in the world to receive this particular gene therapy for his condition, as part of the trial led by Claire and her team. The ongoing clinical trial, along with the development and preclinical testing that made it possible, has been funded by the UCL Technology Fund, managed by AlbionVC in collaboration with UCL Business.

The effect on Remi’s life has been dramatic. “It’s a big, big change,” says Remi. “I can just live my life, reach my goals and pursue what the future has to hold.” This change is felt every day in simple moments. “For most people, going to the park or going to the sea is quite normal. But for me, it’s like a luxury now.”

The benefits extend beyond individual patients. For families, gene therapy can bring greater stability and reduce uncertainty. For healthcare systems, it opens up new ways to treat conditions that were once very difficult to manage.

And its influence reaches further still. As Claire explains, working in rare diseases often leads to wider breakthroughs:

“One of the best things is that whilst you’re working on diseases that are individually very rare, you can learn things that are transferable to other conditions, and importantly you can learn things that are transferable to common diseases as well.” 

She adds that this is why the field matters so much: “Whilst it might only particularly treat a handful of patients with that condition, the implications and the ripple effect of treating and finding out about that condition can be huge.”

Despite important progress, challenges remain. One of the biggest is access. Even when therapies are shown to be safe and effective, making them widely available can be difficult – especially for ultra-rare conditions.

Cost is a significant barrier. Many gene therapies are expensive to develop and deliver, sometimes costing millions per treatment. They also require specialist facilities and expertise.

Researchers are exploring new approaches, including in vivo gene therapy, which could deliver treatment directly into the body and make it simpler and more scalable.

“The next step is making them available to more patients,” says Claire. 

For Remi, the change already feels like a clear dividing line. “I would say like a second life, two separate lives to be honest,” he says.

For many others, that second life is still to come.