For the first time, doctors successfully treat one of the world's most devastating diseases

A man carrying the gene for the condition described the results as 'astounding'

Doctors have successfully treated a severe genetic disease that impacts around 41,000 Americans.

Huntington's disease is a disorder that impairs a person's physical, mental, and emotional capacities, with the BBC describing it as a combination of dementia, Parkinson’s, and motor neurone disease.

The disease, which affects more than 40,000 Americans, according to the Huntington's Disease Society of America, destroys brain cells by altering a protein called Huntington's protein. It is hereditary, with a child having a 50/50 chance of inheriting it if a parent carries the gene.

The National Health Service (NHS) reports that symptoms typically begin between the ages of 30 and 50; however, researchers have succeeded in slowing it down by up to 75 percent for the first time.

A team at University College London disclosed that individuals who would usually experience a year's decline in their condition would now take four years to reach the same stage after treatment.

Side-by-side brain scans: the left shows a healthy brain, while the right illustrates brain matter loss due to neuron death in Huntington's disease (UCLH)

"We never imagined a 75% reduction in clinical progression," Professor Sarah Tabrizi, director of the University College London Huntington's Disease Centre, told the BBC.

The breakthrough, which Tabrizi describes as 'spectacular', involves gene therapy administered directly into the brain during a lengthy 12 to 18-hour surgery.

A modified virus is utilized to deliver new genetic instructions, spreading from one brain cell to another and aiding in blocking the protein responsible for Huntington’s disease.

The procedure involved 29 patients, and after three years, data indicates that fewer brain cells are dying, and the progression of the disease has significantly slowed.

One participant, who had previously retired on medical grounds, has returned to work, and several others in the trial continue to walk, despite expectations that they would need a wheelchair.

"This is the outcome we’ve been hoping for," said Professor Ed Wild, a consultant neurologist at the National Hospital for Neurology and Neurosurgery at University College London Hospitals NHS Foundation Trust.

For individuals like 30-year-old Jack May-Davis, the news is transformative. May-Davis inherited the Huntington’s gene from his father, Fred, who passed away in 2016 after years of decline, and his grandmother.

Jack May-Davis (center) inherited the gene from his father and grandmother (PA)

The Brit expressed the challenge of witnessing his father's health decline to the extent that he required constant care, stating: "It was really awful and horrible."

After participating in UCL's research, the barrister clerk mentioned that the breakthrough has left him 'overwhelmed' as he can finally make future plans.

“It does allow me to think my life could be that much longer," he added.

The therapy is anticipated to be costly and may not be suitable for everyone, but researchers believe it could 'last for life'. UniQure, the company behind the treatment, announced plans to apply to the US Food and Drug Administration (FDA) early next year, seeking accelerated approval to market the drug, with applications in the UK and Europe to follow.