Three-year-old boy with rare disorder now makes his own enzymes

Ollie Chu was three years old when doctors infused edited cells into his body through a catheter. Within months, he stopped needing the weekly drug treatments that had structured his entire life. Now he rides a tricycle, plays with friends, and does what most three-year-olds do: be three.

Ollie has Hunter syndrome, a rare inherited condition where the body can't produce an enzyme called iduronate-2-sulfatase (IDS). Without it, complex sugars accumulate everywhere—lungs, liver, skin, brain. Joints stiffen. Airways narrow. The brain struggles to develop. Most children diagnosed don't live past 20.

For decades, the options were grim. One drug on the market counteracts some symptoms but requires weekly infusions for life and can't reach the brain. Another is bone marrow transplant—risky for toddlers, dependent on finding a matching donor, and rare to find one at all.

Ollie's treatment is different. Researchers at the University of Manchester took his own blood stem cells, used a modified virus to insert a working copy of the IDS gene directly into their DNA, and infused the edited cells back into his body. The cells now produce the enzyme he was born without.

How a Cell's Waste System Works

Think of lysosomes as a cell's stomach. These bubble-like structures contain acidic fluids and enzymes that break down different molecules—fats, proteins, sugars. IDS is one of those cleanup enzymes. In Hunter syndrome, it's missing entirely.

Here's what makes gene therapy different from enzyme replacement therapy: IDS loves to move. It doesn't stay in one cell. If only some cells produce it, the enzyme spreads to neighboring ones. That roaming quality is crucial. It means edited stem cells can generate IDS that travels throughout the body and even—with the researchers' modification—crosses into the brain, where standard enzyme infusions cannot go.

From Lab to Life

In late 2024, Ollie's doctors collected his blood stem cells, edited them in the lab, and infused two doses back through a catheter while he watched cartoons. He went home a few days later.

Three months after the infusion, he came off the weekly drug regimen entirely. His speech improved. His motor control sharpened. His mother, Jingru, told the BBC: "I want to pinch myself every time I tell people that Oliver is making his own enzymes."

Ollie is one of five very young children in an ongoing clinical trial led by the Royal Manchester Children's Hospital. The approach uses the child's own cells, which means no donor matching, no immune rejection risk, and—critically—a one-time treatment instead of a lifetime of infusions.

If the trial succeeds, the same gene-editing method could work for other inherited diseases where stem cells are involved. The researchers aren't stopping at Hunter syndrome. They're building a template.