Investing.com -- Shares of gene therapy developer uniQure N.V. (NASDAQ: QURE) cratered 64% Tuesday morning following an updated data readout for its experimental Huntington’s disease treatment, ifezuntirgene inilparvovec (AMT-130). While the treatment continued to show a dose-dependent slowing of disease progression, a failure to hit statistical significance on a primary clinical measure at 48 months triggered a massive sell-off.

The severe market reaction hinged directly on the four-year data from 12 high-dose patients. The composite Unified Huntington’s Disease Rating Scale (cUHDRS)—a standard measure of cognitive, motor, and functional decline—showed a 44% slowing of disease progression compared to an external control group. However, this result yielded a non-significant p-value of 0.144. In the biotech sector, missing statistical significance on a major endpoint at a late-stage timepoint routinely sparks heavy selling pressure.
uniQure attributed this statistical miss to "survivor bias" within its updated ENROLL-HD matched external control dataset. As patients in the control group progressed in their disease, 53% dropped out of the study by month 48. This attrition left a disproportionately healthier control group, mathematically shrinking the comparative gap between the treated patients and the controls.

A post-hoc analysis utilizing a prior external control dataset restored statistical significance, showing a 54% slowing on the cUHDRS (p=0.041). However, regulatory bodies and investors typically apply heavy discounts to after-the-fact statistical adjustments.

Despite the negative market reaction, the foundation of uniQure’s regulatory strategy remains intact. The FDA previously agreed that the 36-month data would serve as the primary clinical basis for uniQure’s Biologics License Application (BLA) under the accelerated approval pathway, which the company has already submitted.

The updated 36-month analysis, which now includes 15 high-dose patients, delivered robust statistical strength. It demonstrated an 80% slowing of disease progression based on the cUHDRS (p=0.005) and a 67% slowing based on Total Functional Capacity (p=0.011). Because the regulatory filing hinges on this highly significant 36-month data, the drug’s accelerated approval prospects may be largely insulated from the 48-month statistical noise.

For patients and clinicians, the most crucial metric is Total Functional Capacity (TFC), which tracks a patient’s ability to maintain employment, manage finances, and perform daily self-care.

At 48 months, high-dose patients maintained a 61% slowing of functional decline on the TFC metric, securing a strong nominal p-value of 0.008. The data also reinforced a clear dose-dependent response, with high-dose patients outperforming low-dose patients by 1.03 points on the cUHDRS and 0.40 points on the TFC at four years. In clinical development, dose-dependent efficacy is a strong indicator of an active therapeutic effect rather than a chance outcome.

Ifezuntirgene inilparvovec continues to exhibit a generally manageable safety profile, though it carries risks inherent to delivering viral gene therapies directly to the central nervous system. Five high-dose participants (17%) experienced treatment-related serious adverse events involving localized brain inflammation, all of which resolved.

Additionally, a low-dose patient committed suicide approximately five years post-treatment. While tragic, the event was deemed unrelated to the treatment by the study investigator, as suicidal ideation and completion occur at substantially elevated baseline rates among patients with Huntington’s disease.

Original Article