In a London operating theatre, patients with a brutal inherited brain disorder are undergoing an experimental surgery that once seemed science fiction.
The operation involves a single injection deep into the brain, backed by years of genetic research, and early results are shaking up what doctors thought was possible for an incurable condition.
A rare hereditary disease that rewrites families’ lives
Huntington’s disease is a rare but devastating genetic disorder that destroys nerve cells in the brain over many years. One mutated gene is enough to trigger it. A parent who carries the faulty gene has a 50% chance of passing it on to each child.
The mutation affects a gene called HTT on chromosome 4. This gene normally instructs brain cells to make a protein named huntingtin, which plays roles in neuron health and communication. When the gene carries an abnormal sequence, the protein becomes malformed and toxic.
This toxic huntingtin builds up inside neurons, especially in brain regions controlling movement, thinking and emotions. Over time, these cells die off, leading to a progressive and irreversible loss of brain tissue.
Symptoms usually appear between ages 30 and 50. People may first notice mood changes such as irritability, anxiety or depression. Then come involuntary, jerky movements known as chorea, difficulty with fine motor skills, and gradually worsening problems with memory, planning and concentration.
The course of the disease is relentless. From the first clear signs, life expectancy typically ranges from 15 to 20 years. During that period, patients lose independence, often need full-time care and see their personality and abilities change in ways that are painful for families to witness.
In the UK, an estimated 6,000 to 10,000 people are living with Huntington’s disease. Another 20,000 or so may carry the faulty gene without yet knowing it. Genetic testing can confirm the mutation long before symptoms appear, but many at-risk individuals avoid testing because there has been no treatment that changes the long-term outlook.
Until now, medical care for Huntington’s has focused on easing symptoms, not on slowing the underlying disease.
Drugs can reduce chorea, treat depression or help manage psychosis. Physiotherapy and occupational therapy can support mobility and daily activities. None of these approaches alter the genetic cause or the speed of brain degeneration. That context explains why a new gene therapy, AMT-130, is attracting so much attention.
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A single-shot gene therapy that targets the cause
The experimental treatment AMT-130 takes a radically different route from standard medications. It attempts to switch off the brain’s production of the toxic huntingtin protein, going straight for the biological trigger of the disease.
The therapy uses a modified virus as a microscopic delivery vehicle. Scientists at Dutch biotech company uniQure reengineered an adeno-associated virus (AAV) so it can no longer cause disease. Instead, it carries a piece of therapeutic DNA into nerve cells.
This DNA segment instructs neurons to produce a small strand of genetic material called a microRNA. Once inside the cell, the microRNA latches onto the messenger RNA that would usually be used to build the faulty huntingtin protein. That binding stops the cell’s machinery from reading the toxic recipe.
This process, known as RNA interference, has been widely studied in laboratories, but applying it safely and precisely in the human brain at this scale is a major step forward for Huntington’s disease.
Brain surgery that takes up to 20 hours
Delivering AMT-130 is not as simple as a quick injection in the arm. Patients undergo a lengthy neurosurgical procedure lasting between 12 and 20 hours.
Under real-time MRI guidance, surgeons thread two ultra-fine catheters into deep brain structures called the caudate nucleus and the putamen. These areas are among the earliest and most severely affected in Huntington’s disease.
Once the catheters are in place, the viral vector containing the therapeutic DNA is slowly infused. The pace is deliberately cautious to allow the virus to spread through brain tissue while keeping inflammation and immune reactions under control.
The strategy is bold: one brain surgery, one infusion, with the goal of a long-lasting genetic reset inside vulnerable neurons.
Because neurons rarely divide or renew themselves, researchers expect the introduced DNA to remain active for years. Professor Ed Wild, neurologist and co-leader of the trial at University College London Hospitals (UCLH), has described the intended effect as potentially permanent for the treated cells.
What the phase III trial is showing so far
The current phase III trial of AMT-130, coordinated by the Huntington’s Disease Centre at University College London in partnership with uniQure, involves 29 patients across multiple hospitals. They received either a low or high dose of the treatment.
Three years after surgery, those given the higher dose appear to be doing significantly better than would normally be expected. Using a composite clinical score that tracks movement, cognition and day-to-day independence, researchers report a 75% slowing in disease progression.
In practical terms, Huntington’s disease typically causes a clear, measurable decline on these scores each year. People in the high-dose group either remained relatively stable or declined much more slowly. The team estimates that this could translate to roughly four years of preserved function for every year that would usually be lost.
Individual stories hint at the human impact behind the numbers. In one documented case, a woman who had already quit her job due to symptoms reportedly returned to work after treatment, something clinicians did not expect to see in this disease.
Biomarkers suggest real protection of neurons
Clinical scores tell one part of the story. Biomarkers in the spinal fluid add another layer. Patients who received AMT-130 showed a marked drop in levels of neurofilament light chain, a protein that leaks out when neurons are damaged or die.
In untreated Huntington’s, neurofilament levels usually rise by about a third over time as degeneration accelerates. Seeing them fall instead suggests that the therapy is slowing or reducing the ongoing loss of brain cells.
Falling neurofilament levels are a strong hint that AMT-130 is not only easing symptoms but altering the disease biology.
Side effects so far look manageable. Some patients experienced headaches and short-term confusion linked to inflammation after the viral infusion. These episodes responded to steroid treatment or settled on their own. No deaths or severe complications directly attributed to AMT-130 have been reported at this stage.
The results remain preliminary and have not yet gone through full peer review. Still, the data released publicly were considered solid enough for uniQure to prepare a submission to the US Food and Drug Administration (FDA), with a view to seeking approval around 2026.
Costs, access and unanswered questions
Behind the excitement, major questions remain about who will actually receive AMT-130 and under what conditions.
Gene therapies are currently among the most expensive medical products on the market. A single-dose treatment for haemophilia B, for instance, carries a price tag of around €2.6 million per patient. No official figure has been set for AMT-130, but health systems are already bracing for difficult negotiations.
The procedure’s complexity adds another barrier. Very few centres have neurosurgical teams experienced in ultra-long, MRI-guided intracerebral infusions. Scaling up access would require specialised training, dedicated facilities and significant investment.
- High per-patient cost, likely in the millions
- Need for highly trained neurosurgical teams
- Limited number of centres able to perform the operation
- Modest trial size: 29 patients so far
- Unknown long-term safety over decades
The small trial size means rare side effects might not yet have surfaced. Long-term follow up will be crucial. As treated patients age, clinicians will watch for late complications such as immune reactions, unexpected brain changes or interactions with other treatments.
Could this approach prevent disease before it starts?
One of the boldest ideas now being discussed is using AMT-130 not only in people with clear symptoms, but in those who carry the mutated HTT gene yet remain well. Researchers refer to this presymptomatic stage as “Huntington zero”.
In this group, brain changes are already detectable on advanced scans and subtle tests long before chorea or memory problems appear. Treating earlier could, in theory, delay the onset of symptoms by many years, or perhaps prevent them in some cases.
Sarah Tabrizi, who directs the Huntington’s Disease Centre at UCL, is preparing a prevention trial targeting these at-risk individuals. Such a study will face sensitive ethical questions: should someone in their twenties or thirties, who feels healthy, undergo major brain surgery on the basis of a genetic test result?
Preventive use of AMT-130 would shift Huntington’s from a fatal destiny to a condition managed long before it causes visible damage.
Risk-benefit calculations will look very different for prevention than for late-stage disease. Regulators and ethics committees will scrutinise the evidence carefully, particularly around long-term safety and the psychological burden placed on gene carriers asked to make such a profound decision.
What this could mean for other brain diseases
Scientists are also looking beyond Huntington’s. The basic idea behind AMT-130 — targeting a harmful protein at its genetic source, using a one-off brain-directed therapy — could, in principle, be adapted for other conditions where rogue proteins drive damage.
Researchers mention Parkinson’s disease, some inherited forms of Alzheimer’s, and spinal muscular atrophy as potential candidates. Each of these disorders involves specific proteins that misfold or build up in brain or nerve cells.
A tailored microRNA or similar RNA interference strategy could be designed to reduce the production of a different abnormal protein in each case. The same type of viral vector and surgical delivery might then be used, with adjustments for the brain areas most affected.
| Condition | Target protein | Potential role for gene therapy |
|---|---|---|
| Huntington’s disease | Mutant huntingtin | Lower toxic protein to slow neuron loss |
| Parkinson’s disease | Alpha-synuclein | Reduce buildup linked to motor symptoms |
| Inherited Alzheimer’s | Amyloid precursor protein or tau | Limit protein changes that trigger early dementia |
| Spinal muscular atrophy | SMN protein deficit | Boost levels to protect motor neurons |
Any such translation will take years. Each disease comes with its own biology, safety concerns and ethical debates. Still, the Huntington experience provides a real-world testbed for technologies that once existed only in mouse models.
Key concepts patients will hear more often
For families affected by Huntington’s, new jargon can feel overwhelming. Two terms in particular are likely to crop up in conversations with specialists.
RNA interference is a natural mechanism cells use to fine-tune which proteins they produce. Therapies like AMT-130 harness this mechanism to silence or reduce specific genes. The challenge is to cut down the harmful protein without causing widespread disruption to other cellular functions.
Neurofilament light chain is a structural protein inside nerve fibres. When neurons are injured or die, fragments seep into the cerebrospinal fluid and blood. Measuring its levels offers a kind of “thermometer” for ongoing damage in the nervous system. Falling levels under treatment suggest that fewer neurons are being lost.
In the coming years, people attending Huntington clinics may face nuanced choices. Some might opt for gene therapy early, hoping to preserve employment or parenting roles. Others may prefer to wait for more data, fearing rare complications. Health services will need to support not just the medical side, but the psychological strain of such high-stakes decisions.
For now, AMT-130 does not erase the realities of living with a hereditary brain disorder. It does, though, crack open a door that once seemed sealed: the idea that a single, targeted injection into the brain can meaningfully slow a disease that used to feel unstoppable.