Three-year-old Oliver Chu from California became the first child in the world to receive a revolutionary stem cell gene therapy for Royal Manchester Children's Hospital, marking a turning point in the fight against Hunter syndrome, a rare and devastating genetic disorder. The procedure, performed in late 2024 and reported by BBC News in November 2025, didn’t just treat symptoms—it rewrote the future for a boy who, just months earlier, was losing ground to a disease that steals both movement and memory.
A disease that steals childhood
Hunter syndrome, or Mucopolysaccharidosis type II (MPS II), affects roughly 1 in 100,000 to 1 in 150,000 male births. It’s caused by a missing enzyme—iduronate-2-sulfatase—that normally breaks down complex sugars. Without it, those sugars pile up like toxic debris in organs, bones, and crucially, the brain. Children develop coarse facial features, joint stiffness, heart problems—and then, the worst part: a slow, cruel cognitive decline that mimics early-onset dementia. Before this therapy, families had one option: weekly infusions of Elaprase, a drug that helps the body manage the buildup but can’t reach the brain. For Oliver, those infusions were a routine, exhausting part of life.The Manchester breakthrough
At the Manchester Centre for Genomic Medicine at Saint Mary's Hospital, a team led by Professor Simon Jones, Consultant in Paediatric Inherited Metabolic Disease, spent 15 years perfecting a solution. The idea? Take Oliver’s own stem cells, fix the broken gene in a lab, and give them back—with a tiny molecular tag attached. That tag acts like a GPS, guiding the repaired enzyme straight through the blood-brain barrier, something no previous treatment could do. The process took three hours to harvest the stem cells, then weeks in the lab to edit them. After a brief hospital stay for the reinfusion, Oliver recovered quickly. By spring 2025, his parents noticed something unbelievable: he was laughing louder, climbing higher, recognizing faces he’d forgotten. His speech returned. His eyes, once glazed with confusion, now sparkled with curiosity. "Every time we talk about it, I want to cry because it’s just so amazing," said his mother, Jingru Chu. "He’s not just stable—he’s thriving. We didn’t think we’d see this."What the numbers show
The science behind the miracle is just as powerful as the results. Blood tests showed enzyme levels in Oliver’s system were now five times higher than the therapeutic threshold—and they’re staying there. No more weekly infusions. No more needles. No more watching your child slip away. "We’re seeing enzyme levels that are not just detectable, but sustained," said Professor Jones. "This isn’t a band-aid. It’s a reset. The cells are now factories, making their own enzyme, day after day." That’s the game-changer. Previous therapies required lifelong treatment. This one? It could be permanent. And because the enzyme now reaches the brain, it’s not just slowing decline—it’s potentially reversing it.
What this means for families worldwide
There are only about 2,000 boys alive today with severe Hunter syndrome. But for them, this therapy could mean the difference between a life confined to wheelchairs and hospital visits—and one spent playing soccer, learning to read, growing up. "There are very few times where your child can have a reset on life," said Oliver’s father. "So if you can give them that chance, then it’s just something you do." The University of Manchester team is now preparing for a broader clinical trial, with plans to treat up to 12 more children across Europe and North America. Early interest has already come from Canada, Australia, and Japan. The treatment’s cost is still under evaluation, but the researchers are working with insurers and governments to make it accessible.What’s next?
Oliver’s progress is being monitored monthly. His brain scans show signs of reduced sugar buildup. His motor skills are now on par with peers. He’s started preschool. His parents say he’s just… a kid again. But the real test? Time. Will this therapy hold? Will the enzyme keep producing? Will his cognitive gains continue? Researchers believe the answer is yes—but they’re not rushing to declare victory. "We’ve seen miracles," said Professor Jones. "Now we have to make sure they last." If this holds, it won’t just be a treatment for Hunter syndrome. It could be a blueprint for treating other lysosomal storage disorders—like Sanfilippo or Hurler syndrome—that also attack the brain. The same tagging technique? It might work for them too.Frequently Asked Questions
How does this gene therapy differ from enzyme replacement like Elaprase?
Elaprase is a weekly IV infusion that helps manage body-wide symptoms but cannot cross the blood-brain barrier, so it doesn’t stop cognitive decline. This new therapy modifies the child’s own stem cells to produce a modified enzyme with a molecular tag that actively targets the brain, offering a one-time, potentially lifelong solution that addresses both physical and neurological symptoms.
Who is eligible for this treatment, and when will it be available?
Currently, the therapy is only available to children under five with severe Hunter syndrome who have not yet suffered irreversible brain damage. A multi-center trial is set to begin in 2026 across the UK, US, and EU, with expanded access expected by 2027. Regulatory approval will depend on long-term safety data from Oliver’s case and the next dozen patients.
Why did this work in Manchester and not elsewhere?
The University of Manchester team spent over a decade refining the enzyme tag design and stem cell delivery method. While other labs focused on gene editing alone, Manchester’s innovation was adding the specific molecular signal that guides the enzyme into the brain—a breakthrough that required deep collaboration between geneticists, neurologists, and bioengineers.
What are the risks of this therapy?
The procedure carries standard risks of stem cell transplants: infection, graft failure, or immune reactions. There’s also a theoretical risk of unintended gene edits, though the team used a targeted viral vector with no evidence of off-target effects so far. Oliver experienced no serious side effects beyond temporary fatigue after the infusion.
Can girls benefit from this treatment too?
Hunter syndrome is X-linked, so it overwhelmingly affects boys. Girls are typically carriers and rarely show severe symptoms. While the therapy could technically work in girls with rare, severe presentations, current eligibility is focused on boys with classic, early-onset disease—the group most in need.
What’s the long-term outlook for Oliver?
Doctors now believe Oliver has a realistic chance of living a full, independent life—something once unthinkable for children with severe Hunter syndrome. His cognitive and motor milestones are normalizing. If enzyme levels remain stable, he may never need another treatment. His case is now the benchmark for what’s possible.
