AMT-130 at Four Years: Hopeful Signs, Complex Controls

UniQure’s gene therapy AMT-130 (also known as ifezuntirgen inilparvovec) has been a topic of intense discussion for the HD community over the past year. The FDA’s response to 3-year clinical trialclinical trial Very carefully planned experiments designed to answer specific questions about how a drug affects human beings data in September, 2025 prompted community engagement, regulatory re-evaluation, and ultimately, submission for approval in the United States (US) and United Kingdom (UK). On September 29^th, 2026, uniQure shared a press release and presentation with data at the 4 year timepoint of their ongoing trial. 

The data remains positive overall, continuing to suggest that the drug can slow aspects of the progression of HD over time. A path to approval is in sight, but there’s a lot of nuance in the analysis of participants against groups of controls, which could influence next steps. Let’s get into it. 

The strategy

HD is caused by an expanded stretch of the genetic letters “C-A-G” within Huntingtin, a single gene within the vast library of our cells’ DNA. The lengthened gene is made into an extra-long RNARNA the chemical, similar to DNA, that makes up the ‘message’ molecules that cells use as working copies of genes, when manufacturing proteins. message, leading to the production of an expanded form of the huntingtin proteinhuntingtin protein The protein produced by the HD gene.. Expanded huntingtin is widely believed to be toxic to neuronsneuron Brain cells that store and transmit information, especially those that are vulnerable in HD. The basic aim of all huntingtin-lowering strategies (AMT-130 among them) is to decrease the amount of expanded huntingtin proteinhuntingtin protein The protein produced by the HD gene., reducing potential harm to brain cells.

The drug

AMT-130, developed by uniQure, is the first experimental HD gene therapy to be tested in humans. It is packaged into a harmless virus called an AAVAAV a virus that can be used to deliver gene therapy drugs to cells. AAV stands for adeno-associated virus. that is delivered via brain surgery to vulnerable areas of the brain. This AAVAAV a virus that can be used to deliver gene therapy drugs to cells. AAV stands for adeno-associated virus. delivers specially designed genetic material that prevents huntingtin RNARNA the chemical, similar to DNA, that makes up the ‘message’ molecules that cells use as working copies of genes, when manufacturing proteins. messages from creating the huntingtin proteinhuntingtin protein The protein produced by the HD gene.. The goal is to permanently lower the amount of huntingtin proteinhuntingtin protein The protein produced by the HD gene. produced by brain cells, both the regular and expanded forms.

The trial

The first arms of uniQure’s trial of AMT-130 involved around 40 people with early-stage HD, and after adding more groups, more than 50 have now received the gene therapy. All participants underwent brain surgery; most received either a high dose or a low dose of AMT-130, though some had a “sham” surgery in which no drug was delivered. After 1 year, many of those who had sham surgery were eligible to receive AMT-130. Twenty-four participants have now been living their lives for 4+ years after receiving the drug, and uniQure continues to follow everyone in the study and to add more participants. The focus of the most recent announcement was the 4-year data, which centred on 12 participants in the high-dose group.  

The turmoil

For a more thorough recap of previous study milestones, check out HDBuzz’s June 2026 article. Briefly, in September 2025, uniQure reported that people who received a high dose of AMT-130 appeared to progress more slowly than matched people in natural history studies, 3 years post-surgery. This was encouraging news, though the comparison had limitations. The path to approval became less clear when in March 2026, the FDA appeared to have changed its position on the trial’s design and measures.

The application

The HD community rallied, uniQure stood by their findings, and in June 2026, the company announced that the FDA had agreed its existing three-year trial data could serve as the primary basis for an application to approve AMT-130. The company still needs to align with the FDA on the design of a follow-up study to confirm the drug’s benefit, but the announcement offered a clearer path toward submitting the application.

The important question is whether the evidence as a whole consistently points towards a meaningful treatment effect

Then, on September 2nd, 2026, uniQure announced that it had indeed submitted a Biologics License Application to the US FDA, and a Marketing Authorisation Application to the UK MHRA. The announcement also introduced many in the HD community to AMT-130’s official generic name: ifezuntirgene inilparvovec. It’s a mouthful that we are glad to chew on, if it represents a disease-modifying drug for HD!

A submission is NOT a guarantee, but IF these applications are ultimately successful, they would lead to approval of AMT-130 in the US and UK. 

The newest data

The overall messaging shared in uniQure’s most recent announcement is that, at 4 years post-surgery, the high dose of AMT-130 has continued to suggest an ability to slow HD in comparison to a group of Enroll-HD participants who did not receive the drug. Using cUHDRS, the estimated slowing was 44%. However, this difference was not statistically significantstatistically significant Unlikely to have arisen by chance, according to a statistical test, meaning the data are not strong enough to confidently rule out the possibility that the apparent difference arose by chance. With only a small number of people followed for 4 years, there is uncertainty around this estimate, so the 44% figure should be interpreted cautiously.

There also seem to be signs of dose dependency, meaning simply that higher doses have stronger effects. Seeing a larger effect with a higher dose can strengthen the case that a drug is having a meaningful biological effect. After 4 years, the high dose AMT-130 group (12 participants) performed better than the low dose AMT-130 group (also 12 participants). 

All that said, interpreting the results remains complex given the small group of participants and the limitations of the control data used in the different analyses uniQure have shared.

Measuring change

The primary endpointprimary endpoint The main question asked in a clinical trial, the key measurement of HD progression in the uniQure study, was a combined score known as the cUHDRS. It captures measurements of thinking and movement symptoms across multiple tests: Total Functional CapacityTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks (TFCTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks), which queries day-to-day abilities, SDMT and SWRT, which measure speed of thinking and decision-making, and TMS, which measures movement symptoms like choreachorea Involuntary, irregular ‘fidgety’ movements that are common in HD. These individual tests were considered to be secondary endpoints – valuable to examine in the study, but of slightly lower importance. 

It’s particularly important to understand the comparison that this study makes in the analysis of participant data. Those who received AMT-130 were compared to participants in Enroll-HD, a huge HD “natural history” study that simply follows people over time, with no drug involved. Depending on exactly how you slice the data, there are several hundred to more than a thousand Enroll-HD participants who have 1) similar characteristics as the twelve uniQure study participants, 2) consistently completed the same tests, and 3) stayed in the study for at least 4 years. 

Complex findings

Overall, the data are positive, but complex. The main hiccup is the stats we mentioned above: while average cUHDRS scores in those who’d gotten a high dose of AMT-130 seemed to decline at a slower rate than in similar Enroll participants (good news) the overall change in this key measure didn’t reach statistical significance at 4 years. 

On the other hand, there was a significant 61% slowing in TFCTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks decline, suggesting that participants’ ability to carry out day-to-day activities remained relatively stable. uniQure and many of the HD clinical leaders they partnered with to run the study have placed strong emphasis on this finding, noting that little to no loss of function is particularly meaningful for people with HD and their loved ones.

Other individual tests from within the cUHDRS also showed nuanced results. AMT-130 does not appear to slow changes in movement symptoms after 4 years compared to the Enroll-HD natural history data, nor a thinking measure called SDMT, but there was a big slowing of progression in another thinking and reading test called SWRT. 

Different controls at 4 years

Enroll-HD is an ongoing study, and new data updates are released periodically. uniQure submitted their applications for approval of ifezuntirgene inilparvovec (AMT-130) based on their three-year data, which used earlier Enroll data that uniQure is calling “Enroll-HD A.” The recent four-year data uses the most recent update, called “Enroll-HD B.” 

They noticed something important about the new Enroll-HD dataset B versus the older Enroll-HD dataset A: the B group seemed to have a slower disease trajectory. They thought this might understate how much decline happens over the course of 4 years with HD. So uniQure decided to re-compare their 4-year data from the 12 participants in the high-dose AMT-130 group to the Enroll-HD dataset A. 

With only 12 high-dose participants in the four-year analysis, these findings deserve both hope and careful scrutiny.

When they did that, cUHRDS showed a statistically significantstatistically significant Unlikely to have arisen by chance, according to a statistical test, 54% slowing of disease progression, and an even bigger effect (68%) on slowing of TFCTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks. This is known as a post-hoc (after-the-fact) analysis, because it was not planned beforehand – the study was not originally designed to study multiple control groups.

Why might the newer control group look different? One major issue is missing data. By four years, lots of the relevant follow-up data were missing from the updated Enroll-HD comparison group. Importantly, it is suspected that the people who dropped out may have had faster-progressing HD than those who remained. This could leave behind a comparison group that looks healthier and declines more slowly than we might otherwise expect.

This could explain why the estimated size of AMT-130’s effect changes depending on which Enroll-HD dataset is used. It also highlights why we shouldn’t get too attached to a single headline percentage. The important question is whether the evidence as a whole consistently points towards a meaningful treatment effect.    

More 3-year data

Not everyone begins participating in a clinical trialclinical trial Very carefully planned experiments designed to answer specific questions about how a drug affects human beings at exactly the same moment, especially when there’s a complex brain surgery to consider. There is now 3-year data available from three additional participants, which also formed part of uniQure’s recent release. This update is particularly encouraging. There seems to be a slowing of disease progression compared to the new Enroll-HD dataset B, not only in cUHDRS and TFCTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks, but in SDMT and SWRT, with a positive trend in TMS (though this movement score didn’t reach statistical significance). 

The regulatory submission for approval was based on 3-year data, so this is a good sign, and follows the same trend we’ve been seeing. But it’s also a reminder that in a tiny group of participants like this, averages can change on a dime.    

Safety and health of neuronsneuron Brain cells that store and transmit information

Many other measures of safety and the action of the drug on HD biology were also collected over the course of the study – and as a reminder, this small study was originally designed to test safety, not changes in symptoms. 

The overall data and messaging of positive trends for HD symptoms has remained consistent, but the statistics differ depending on the control group.

The main safety concerns were after the surgery itself, when brain inflammationinflammation Activation of the immune system, thought to be involved in the HD disease process and other complications were closely monitored after the procedure. It was also common for participants to experience headaches and pain after the collection of spinal fluid. Of those who underwent surgery years ago, no new safety issues have come up; one more recent participant had brain inflammationinflammation Activation of the immune system, thought to be involved in the HD disease process after surgery, which resolved with steroid medication. uniQure also shared that one participant, treated 5 years ago, very sadly took their own life. The study investigator assessed the death as unrelated to treatment. A difficult reality is that people living with HD are at substantially higher risk of suicide than the general population, making careful monitoring of mental health particularly important in HD clinical trials.

Study measurements included levels of NfLNfL biomarker of brain health in the spinal fluid (CSFCSF A clear fluid produced by the brain, which surrounds and supports the brain and spinal cord.). NfLNfL biomarker of brain health tends to increase as neuronsneuron Brain cells that store and transmit information become sick with HD, as well as with other types of damage to the brain, so it represents one way to track the progression of HD, potential damage after delivery, and the effectiveness of a drug. 

As expected, NfLNfL biomarker of brain health levels went way up right after surgery, but then returned to baseline (pre-surgery) levels over time. As HD symptoms worsen, NfLNfL biomarker of brain health levels usually go up by 10-15% per year, but NfLNfL biomarker of brain health increased by only 4% over 4 years in those who received a high dose of AMT-130. This is also a good sign for safety and potentially reduced damage to the brain. 

The takeaways

Four years after a single treatment, the high-dose AMT-130 group continues to show encouraging signs of slower HD progression, particularly in day-to-day abilities. The updated three-year results and the difference between doses also strengthen the pattern seen in the data supporting uniQure’s applications for regulatory approval. 

With only 12 high-dose participants in the four-year analysis, these findings deserve both hope and careful scrutiny. The original study was designed primarily to demonstrate safety, not to establish whether AMT-130 can slow HD progression. The overall data and messaging of positive trends for HD symptoms has remained consistent, but the statistics differ depending on the control group. This shows why the choice of comparison matters, and underscores the complexity of interpreting data from such a small trial. 

Regulators will weigh the full evidence as they review the applications, and uniQure expects an answer very soon – in the fourth quarter of 2026. We’ll keep our eyes peeled in anticipation of a potentially historic moment for the HD community. 

Summary

• Four years after treatment, high-dose AMT-130 continues to show encouraging signs that it may slow HD progression, although the key cUHDRS result was not statistically significantstatistically significant Unlikely to have arisen by chance, according to a statistical test in the primary four-year comparison. 
• Day-to-day function was improved, with the decline in Total Functional CapacityTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks (TFCTotal Functional Capacity A standardized rating scale for function in HD, used to assess capacity to work, handle finances, perform domestic chores and self-care tasks) significantly slowed by 61% when compared with the updated Enroll-HD control group. 
• Not every measure moved in the hoped-for direction. Movement symptoms and one thinking measure (SDMT) did not show slowing at four years, while another cognitive measure (SWRT) did. 
• The estimated benefit depends on which Enroll-HD comparison group is used. A post-hoc analysis using an older control dataset produced larger, statistically significantstatistically significant Unlikely to have arisen by chance, according to a statistical test effects, highlighting the challenges of drawing conclusions from historical controls and small participant numbers. 
• The overall picture remains encouraging, but uncertainty remains: only 12 people make up the four-year high-dose group, and the original trial was designed primarily to assess safety. Regulators will now consider the totality of the evidence when reviewing AMT-130 for potential approval.