Manchester: Doctors are cautiously celebrating early signs of success from a pioneering gene therapy that could change the outlook for children with Hunter syndrome, a rare and life-shortening inherited disorder.
Three-year-old Oliver Chu from California became the first child to receive the experimental treatment nine months ago as part of a trial led by the Manchester Centre for Genomic Medicine at Saint Mary’s Hospital. While it is too soon to declare a breakthrough, doctors say his progress has been far better than expected.
A Rare Disorder With Limited Options
Oliver was born with Hunter syndrome, a condition caused by a faulty gene that stops the body from producing a vital enzyme used to break down complex sugars. Without it, these sugars build up in organs and tissues, leading to joint stiffness, hearing loss, heart problems, and progressive cognitive decline. Life expectancy for children with the condition is typically between 10 and 20 years.
The only approved treatment, a weekly enzyme replacement infusion called Elaprase, costs hundreds of thousands of pounds a year and must be taken for life. Crucially, the drug does not reach the brain, meaning it cannot halt the decline in cognitive function.
In February, doctors collected stem cells from Oliver’s blood, inserted a working copy of the missing gene, and infused the corrected cells back into his bloodstream. These cells began producing high levels of the enzyme, including inside the brain, something the standard treatment cannot achieve.
Since then, Oliver has been able to stop his weekly infusions altogether. His father says the difference has been remarkable. His life is no longer dominated by needles and hospital visits. His speech, agility, and cognitive development have all improved dramatically. It’s not been a slow progression. It has shot up since the transplant.
A revolutionary stem cell gene therapy treatment for Hunter syndrome has been developed by Manchester researchers.
3-year-old Ollie received the treatment in a clinical study supported by Manchester BRC.
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— NIHR Manchester Biomedical Research Centre (@ManchesterBRC) November 24, 2025
Early Signs Bring Cautious Optimism
Prof Simon Jones, one of the trial’s lead investigators, described Oliver’s progress as hopeful but urged patience. Ollie was the first human to receive this therapy, and it’s only been nine months. We have four more boys scheduled and need to show the benefit lasts, he said.
Oliver’s older brother, Skyler, also has Hunter syndrome. Although the therapy cannot reverse existing damage, doctors believe Skyler may benefit if treated soon, as tests show he has been largely unaffected so far despite being five years old.
Hunter syndrome is extremely rare, affecting about one in 100,000 boys worldwide. The trial’s five participants come from the US, Europe, and Australia. None are from the UK because children here are not diagnosed early enough.
To treat most patients at the right time, we would need newborn screening, Jones said. The test is already routine in the US and is seen as crucial for future gene therapy success. Researchers are now adapting the same approach for other severe genetic disorders, including Hurler and Sanfilippo syndromes.
For Oliver’s family, the transformation over just nine months has already changed daily life. And for doctors, his remarkable progress may be the first sign that a long-sought treatment for Hunter syndrome is finally within reach.
