Full Breakdown
UniQure’s Huntington’s Gene Therapy Shows Diminished Four-Year Efficacy, Prompting Market Sell-off
By Drooid · · How we work
Core Event: Four-Year Trial Results Reveal Non-Significant Slowing on Primary Endpoint
On September 29, Dutch biotech UniQure disclosed updated results from its Phase 1/2 study of the gene-therapy AMT-130 (ifezuntirgene inilparvovec) in Huntington’s disease. In the high-dose cohort of 12 patients, disease progression measured by the composite Unified Huntington’s Disease Rating Scale (cUHDRS) slowed by 44 % relative to an updated external control group, but the difference was not statistically significant (p = 0.144). The secondary Total Functional Capacity (TFC) measure showed a 61 % slowing (p = 0.008). The announcement sent UniQure’s Nasdaq-listed shares down roughly 40 % in pre-market trading.
Background & Context
Huntington’s disease is a rare, inherited neurodegenerative disorder with no approved disease-modifying therapy. AMT-130 delivers a micro-RNA to silence the mutant huntingtin gene via a one-time, MRI-guided brain injection. Earlier data released in September 2025 reported a 75 % slowing on cUHDRS at three years, forming the basis of a biologics license application (BLA) submitted to the FDA in early September 2026 after an eight-month hold was lifted.
Data & Statistics
- cUHDRS (48 mo): 44 % slowing vs. updated ENROLL-HD external control; p = 0.144.
- TFC (48 mo): 61 % slowing vs. same control; p = 0.008.
- Control-group missingness: 53 % of the external cohort lacked 48-month data; UniQure argues faster-progressing patients dropped out, potentially understating the treatment effect.
- Post-hoc analysis (prior control): 54 % slowing on cUHDRS and 68 % on TFC, both statistically significant.
- Safety: Five high-dose participants (17 %) experienced treatment-related serious adverse events of CNS inflammation, all resolved. One suicide occurred in a low-dose patient and was deemed unrelated.
Official Statements & Responses
Chief medical officer Walid Abi-Saab said “survivor bias” in the updated control dataset likely reduced the apparent benefit, while maintaining that the four-year data still demonstrate a “meaningful slowing of disease progression.” CEO Matt Kapusta called the results “unprecedented” and expressed confidence that the BLA will be accepted in the fourth quarter.
Conflicting Reports & Gaps
Efficacy percentages differ depending on the external control dataset: the updated ENROLL-HD set yields 44 % slowing (non-significant) on cUHDRS, whereas the prior dataset produces 54 % slowing (significant). UniQure has not provided a definitive plan to address the 53 % attrition in the control arm.
Why It Matters
If approved, AMT-130 would be the first disease-modifying therapy for Huntington’s disease, affecting an estimated 30,000–41,000 U.S. patients. The mixed four-year data underscore the challenges of demonstrating long-term efficacy in rare-disease gene-therapy trials and affect investor confidence and regulatory risk assessment.
What’s Next
The FDA has granted UniQure priority review, with a decision expected in the fourth quarter of 2026. The company also announced a confirmatory trial of approximately 200 patients, aiming to begin screening before year-end. Results from that study will be critical to validating the four-year findings and securing accelerated approval.
Verbatim Quotes
- “We do think that, beyond three years, the data is really suffering from this survivor bias,” — Walid Abi-Saab, UniQure's chief medical officer
- “As pioneers in this space, we are blazing a new trail in HD, learning and deepening our understanding with every data point we generate,” — Matt Kapusta, CEO.