Three-year-old Oliver Chu, a lively toddler from California, has become the first person in the world with Hunter syndrome to receive a pioneering stem cell gene therapy—an achievement that’s sending waves of hope through the rare disease community. Oliver’s story, which began with a daunting diagnosis and led him across the Atlantic for a groundbreaking clinical trial, is now one of unexpected recovery and renewed optimism for families facing similar genetic challenges.
Hunter syndrome, formally known as mucopolysaccharidosis type II (MPS II), is a rare genetic disorder that disrupts the body’s ability to break down certain sugar molecules. As these molecules accumulate, they cause progressive damage to organs and tissues. According to the Cleveland Clinic, symptoms include stiff joints, thickening facial features, hearing loss, delayed growth, breathing and heart issues, and cognitive decline that mirrors childhood dementia. In its most severe form, Hunter syndrome is life-threatening, with most patients rarely surviving beyond age 20.
For Oliver’s parents, Jingru and Ricky Chu, the diagnosis in April 2024 was a devastating blow—especially since their older son, Skyler, was also born with the same condition. As Ricky recounted to the BBC, “When you find out about Hunter syndrome, the first thing the doctor tells you is 'Don't go on the internet and look it up because you'll find the worst cases and you'll be very, very disheartened.' But, like anybody, you look it up and you're like, 'Oh my goodness, is this what's going to happen to both my sons?'”
Despite the overwhelming uncertainty, the family’s determination never wavered. In December 2024, a new opportunity emerged: a clinical trial at Royal Manchester Children’s Hospital in the United Kingdom, where doctors were testing an experimental stem cell gene therapy. The therapy was described by hospital researchers as “revolutionary”—a potential reset on life for children like Oliver, who otherwise faced a grim prognosis.
The logistics were daunting. Because of his age, Skyler was not eligible for the Manchester trial and instead enrolled in a different study in the United States. This meant splitting up the family, but the Chus were resolute. “Although it was a big commitment to travel to the UK, of course we want the best for our children,” Ricky told hospital staff, as reported by People. “There are very few times where your child can have a reset on life so if you can give them that chance, then it’s just something you do.”
The gene therapy itself is a marvel of modern medicine. Doctors first removed Oliver’s stem cells and sent them to Great Ormond Street Hospital (GOSH) in London. There, scientists used viral machinery to insert a working copy of the faulty gene into each stem cell. As Dr. Karen Buckland of the Cell and Gene Therapy Service at GOSH explained to the BBC, “We use the machinery from the virus to insert a working copy of the faulty gene into each of the stem cells. When those go back to Oliver, they should repopulate his bone marrow and start to produce new white blood cells, and each of these will hopefully start to produce the missing protein [enzyme] in his body.”
In February 2025, Oliver received the genetically modified stem cells via infusion. He was the first of five boys worldwide to undergo this treatment, making him a trailblazer in the fight against Hunter syndrome. The stakes were high, but the results have been nothing short of extraordinary.
Now, just months after the procedure, Oliver’s progress has surpassed even the most optimistic expectations. He is developing normally—both physically and cognitively—a transformation that has left his doctors and parents in awe. Researcher Simon Jones, who is co-leading the trial, told the BBC, “I’ve been waiting 20 years to see a boy like Ollie doing as well as he is, and it’s just so exciting.”
Ricky Chu echoed this sentiment in his statement to the hospital: “Ollie is doing great since having the gene therapy. We have seen dramatic improvements, and he continues to grow physically and cognitively. Our hope for Ollie because of this treatment is that he will continue to make his own enzymes and live a normal life without infusions.”
The emotional toll—and the gratitude—are evident every time the family reflects on their journey. “Every time we talk about it I want to cry because it's just so amazing,” Jingru told People. The couple is “forever grateful” for the chance to participate in the research, and they hope that Oliver’s remarkable outcome will pave the way for more children to benefit, including Skyler. “My wish upon the star is for Skyler, to be able to get the same treatment,” Ricky added. “It feels like Oliver has got a reset in his life, and I want the same thing for Skyler, even though he's a bit older.”
The family’s hope is shared by the medical community. The trial at Royal Manchester Children’s Hospital is one of the first to use stem cell gene therapy for Hunter syndrome, and Oliver’s success could signal a turning point in how the disease is treated. Traditional management has relied on enzyme replacement therapy—regular infusions that can slow the progression of symptoms but rarely halt or reverse the damage. The new gene therapy, by contrast, aims to correct the underlying genetic defect, allowing the patient’s own body to produce the missing enzyme naturally.
For families facing a Hunter syndrome diagnosis, the implications are profound. The promise of a one-time treatment that could restore normal development and eliminate the need for lifelong infusions is nothing short of life-changing. Still, researchers caution that more data is needed. Oliver was the first of five boys to receive the therapy, and ongoing monitoring will determine how durable and widespread the benefits are.
Meanwhile, the Chus are adjusting to a new normal—one filled with hope rather than dread. “Seeing the difference for Ollie pre-and post-transplant has made us believers,” Ricky said. The family’s journey, marked by sacrifice and resilience, has become a beacon for others in the rare disease community. As the research continues and more children are treated, Oliver’s story may soon be just the beginning of a new chapter in genetic medicine.
For now, the Chu family is savoring every milestone, every smile, and every moment that once seemed out of reach. Their experience stands as a testament to the power of science, the strength of family, and the enduring human spirit in the face of daunting odds.
