Groundbreaking Gene Therapy Eliminates Enzyme Deficiency in Child with Hunter Syndrome

A medical team in Manchester has reported highly encouraging outcomes from the world's first application of stem cell-based gene therapy to treat Hunter syndrome, also known as MPS II, a rare genetic disorder. This single-session procedure was administered in February 2025 at the Royal Manchester Children's Hospital.

The first recipient of this clinical trial, designed by researchers at the University of Manchester, is three-year-old Oliver Chu. The treatment regimen commenced in December 2024 with the collection of the patient’s own autologous hematopoietic stem cells. These cells were subsequently transported to the Great Ormond Street Hospital (GOSH) laboratory in London, where they underwent modification using a lentiviral vector to introduce a functional copy of the IDS gene.

A key innovation of this therapy lies in the modified enzyme. It incorporates a short tag engineered to facilitate its passage across the blood-brain barrier. This feature is crucial for addressing the neurological symptoms that conventional treatments have been unable to manage effectively.

As of November 2025, approximately nine months following the intervention, Oliver has demonstrated substantial progress. His weekly infusions of the drug Elaprase have been discontinued. Furthermore, blood tests revealed extremely high levels of the corrective enzyme—reportedly hundreds of times higher than typical reference ranges. Professor Simon Jones, who co-led the research, described these initial results as both long-awaited and profoundly promising.

The development of this therapeutic approach spanned roughly 10 to 15 years. Following the licensing withdrawal of the biotechnology firm Avrobio in 2023, the clinical trials were kept afloat thanks to a vital £2.5 million grant secured from the LifeArc charity.

Hunter syndrome stems from a mutation in the IDS gene, leading to a deficiency of the enzyme iduronate-2-sulfatase. This deficiency causes a buildup of glycosaminoglycans within tissues and organs, resulting in severe, progressive damage and cognitive decline. For those with severe forms of the condition, the typical life expectancy ranges between 10 and 20 years.

The standard treatment, enzyme replacement therapy using Elaprase, is exceptionally costly—around £375,000 annually. However, this therapy cannot halt neurodegeneration because the enzyme struggles to penetrate the blood-brain barrier effectively.

The current study aims to enroll up to five young boys from locations including the United States, Europe, and Australia. At the time the clinical monitoring began, no suitable patients were available within the United Kingdom. Oliver’s parents have reported significant upticks in both their son's physical capabilities and cognitive function.

Professor Rob Wynn emphasized that this gene therapy offers a safer and potentially more effective alternative to traditional bone marrow transplantation. Since it utilizes the patient's own cells, the need to locate a suitable donor is eliminated, and it achieves superior levels of the missing enzyme.

While two years of follow-up observation are necessary to fully gauge the long-term efficacy, the case of Oliver Chu already marks a monumental stride forward. It signals a crucial shift away from purely palliative care toward the possibility of a genuine genetic correction for a devastating hereditary illness.