The parents of a three-year-old boy born with a devastating, life-limiting genetic condition say they are now excited for his future after he received a revolutionary stem cell gene therapy treatment developed by researchers in Manchester and supported by funding from LifeArc.

In February 2025, Oliver (Ollie) Chu, was treated for Hunter syndrome in a clinical study being delivered at Royal Manchester Children’s Hospital (RMCH) in collaboration with the Manchester Centre for Genomic Medicine at Saint Mary’s Hospital – both part of Manchester University NHS Foundation Trust (MFT). The trial is managed and sponsored by The University of Manchester.

Children with Hunter syndrome, a rare, inherited condition also known as mucopolysaccharidosis type II (MPS II), have a change in a gene, meaning they cannot produce an important enzyme that breaks down complex sugar molecules. Over time these sugars build up in organs and tissues, leading to joint stiffness, hearing loss, breathing and heart problems, developmental delays and cognitive decline.

Hunter syndrome can be life-threatening, with life expectancy typically between 10 and 20 years. Currently the only licensed drug that can help to improve life for children with Hunter syndrome is Elaprase – a weekly enzyme replacement therapy that takes approximately three hours to administer, that children must take for their whole life. Approximately 50 patients in the UK receive Elaprase, which costs around £375,000 a year per patient. The drug can reduce mobility and organ problems but cannot improve mental decline.

“A huge challenge for the more than 3.5 million people in the UK living with rare diseases is getting access to effective treatments – currently 95 per cent of conditions have none – this needs to change. Developing innovative treatments like this are one part of the solution but we crucially need to transform how we support rare disease research and development more broadly in the UK. We must act today to demand better, to work together and change the future for the millions of people living with rare diseases.”

Sam Barrell, CEO of LifeArc

Ollie was diagnosed with Hunter Syndrome after five-year-old brother, Skyler, was found to have the condition.

Ollie, who lives in California with mum Jingru, dad Ricky, and Skyler travelled to the UK to be part of the research, after tests showed he was still in the early stages of the condition.

Now, several months on from the procedure, Ollie has fully recovered from the stem cell replacement therapy, and his parents and the Manchester researchers are excited by his progress.

Ricky, Ollie’s dad, said, “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.

“We’re excited for Ollie’s future. Seeing the difference for Ollie pre-and post-transplant has made us believers. We will be forever grateful to the entire research team for allowing us to be part of this research. I’ve been a huge advocate of this trial.”

“For many years we have performed bone marrow transplant for children with Hunter Syndrome and similar illnesses. However, these are difficult procedures that can only deliver as much enzyme as the donor’s blood naturally has. Gene therapy is not only safer and more effective, but it enables us to use the child’s own cells which cuts out the need to find a donor, and means we can produce more enzyme for the patient. The principles of using gene therapy of blood cells to treat patients with this disease can be applied to many other conditions which offers exciting prospects for patients and healthcare professionals. Our medicine is becoming safer, and better, and that can only be a good thing!”

Professor Rob Wynn, Consultant Paediatric Haematologist and Director of Paediatric Bone Marrow Transplant Programme at RMCH and joint study lead

Ollie Chu is the first of five young children with Hunter syndrome to participate in this study. The research is jointly funded by The University of Manchester and LifeArc, a self-funded, not-for-profit medical research organisation. The stem cell therapy was developed by researchers at MFT and The University of Manchester, working in partnership with the University of Edinburgh, Great Ormond Street Hospital (GOSH), and University College London.

“Since having the gene therapy Ollie is no longer having weekly Elaprase infusions, but instead of seeing levels of the previously missing enzyme dropping we are seeing very high levels in his blood, and this is an extremely encouraging sign that the treatment is working. I have worked in researching treatments for children with rare genetic diseases for over twenty years and I have sadly seen many children lose their lives to these devastating conditions. This is a truly exciting development which could lead the way for treating similar genetic conditions and bring hope to other families.”

Professor Simon Jones Consultant in Paediatric Inherited Metabolic Disease at the Manchester Centre for Genomic Medicine at Saint Mary’s Hospital, joint study lead