Vico's VO659 Advances with Twice-Annual Dosing for Huntington's, Ataxia

LEIDEN, Netherlands – February 24, 2026 – Vico Therapeutics, a Dutch biotechnology firm, has initiated patient dosing with a new twice-annual regimen for its investigational drug, VO659. This pivotal step in the ongoing Phase 1/2a clinical trial in Europe aims to establish a more patient-friendly treatment for individuals with Huntington’s disease (HD) and spinocerebellar ataxia (SCA) types 1 and 3. In a concurrent major development, the company announced it has received Investigational New Drug (IND) clearance from the U.S. Food and Drug Administration (FDA), paving the way for clinical trials to begin in the United States later this year and significantly broadening the therapy's global development program.

A Patient-Centric Leap Forward

For patients and families grappling with the relentless progression of neurodegenerative disorders like HD and SCA, the burden of treatment can be as challenging as the disease itself. Vico's shift to a twice-annual dosing schedule for VO659 represents a potential paradigm shift in the management of these conditions. A less frequent treatment schedule promises to dramatically improve quality of life by reducing the number of hospital visits and invasive procedures.

VO659 is administered intrathecally, via a lumbar puncture into the spinal fluid, a necessary route to deliver the therapy directly to the central nervous system. While the procedure itself is medicalized, reducing its frequency from monthly or quarterly to just two times a year could alleviate significant physical and logistical strain on patients and their caregivers. This development is made possible by the drug's inherent properties, which allow it to remain active in the body for an extended period.

“I am very encouraged by our earlier results showing significant reduction of mHTT directly in the central nervous system with a favorable CSF Nf-L profile early in the time course,” said Micah Mackison, CEO of Vico Therapeutics, in a statement. “The twice annual patient-friendly dosing regimens will enable us to assess longer-term safety and pharmacodynamic effects, taking advantage of VO659’s long half-life.”

The European trial will now assess this new regimen over a 12-month period, focusing on long-term safety, tolerability, and the drug's effect on key disease biomarkers. According to the company, the therapy has been safe and well-tolerated in the trial to date, with no serious adverse events reported.

Targeting the Genetic Core of Disease

VO659 is at the forefront of a new wave of genetic medicines known as antisense oligonucleotides (ASOs). These therapies are not mere symptom management; they are designed to intervene at the genetic source of a disease. HD and SCA types 1 and 3 are part of a family of nine polyglutamine diseases, all caused by the same type of genetic error: an abnormal expansion of a DNA sequence known as a CAG repeat. This error leads to the production of toxic, misshapen proteins that accumulate in brain cells, causing progressive neuronal death and the devastating symptoms of these conditions.

VO659 is a synthetic strand of nucleic acid engineered to find and bind to the RNA message that carries the flawed CAG repeat instructions. By binding to this message, the ASO effectively silences it, preventing the cell from producing the toxic protein. A key feature of VO659's design is its allele-preferential nature, meaning it is engineered to primarily target the mutant, disease-causing RNA while largely sparing the healthy version of the protein, which is essential for normal cellular function.

Early data from the trial has already shown promising signs of this targeted engagement. In Huntington's disease patients, Vico previously reported a 38% reduction in the toxic mutant huntingtin protein (mHTT) in the cerebrospinal fluid. This demonstrates the drug is reaching its target and having a direct biological effect. Concurrently, the trial observed a 2.5% reduction in Neurofilament Light Chain (Nf-L), a key biomarker of nerve cell damage. A stable or decreasing level of Nf-L is an encouraging sign that the therapy may be slowing or halting the neurodegenerative process without causing toxicity.

Navigating a Competitive and Hopeful Landscape

The therapeutic landscape for Huntington's disease and spinocerebellar ataxias has long been defined by a lack of disease-modifying options. Current standard-of-care focuses on managing symptoms like involuntary movements (chorea) in HD or balance and coordination issues in SCA. However, a robust pipeline of investigational therapies is now offering real hope for treatments that can slow or stop disease progression.

Vico Therapeutics enters a competitive field populated by major pharmaceutical players and innovative biotech firms. In the Huntington's space, Roche is advancing its ASO Tominersen in a new Phase 2 trial, while companies like Wave Therapeutics and PTC Therapeutics are exploring different genetic and small molecule approaches. For SCA, Biohaven’s Troriluzole is currently under priority review by the FDA, potentially becoming the first approved treatment for the condition.

Within this dynamic environment, VO659's strategy is distinctive. By targeting the CAG repeat itself, the therapy holds the potential to be a "pipeline in a product," applicable to all nine polyglutamine diseases caused by this specific genetic stutter. This broad approach, combined with its allele-preferential design, sets it apart from many competitors focused on a single disease or a non-discriminatory reduction of both healthy and mutant proteins.

Strategic Expansion into the United States

Securing IND clearance from the FDA is a critical milestone that validates Vico's preclinical and early clinical data and unlocks the next phase of its growth. The decision allows the company to expand its clinical program into the United States, the world's largest pharmaceutical market. This move provides access to a larger and more diverse patient population, which can accelerate trial enrollment and data collection.

Initiating U.S.-based trials, planned for later this year, will also enable Vico to collaborate with leading American clinical research centers and neurologists specializing in these rare diseases. This not only enhances the quality and scope of the clinical study but also builds crucial relationships within the U.S. medical community ahead of potential commercialization. Furthermore, a U.S. presence significantly raises the company's profile among American investors, potentially facilitating future funding rounds needed to support late-stage development.

To further disseminate its findings, Vico is presenting detailed updates at the 21st Annual HD Therapeutics Conference this week. Chief Scientific Officer Nicole Datson, PhD, will elaborate on the drug's unique mechanism of action, while Chief Medical Officer Scott Schobel, MD, will provide a clinical update from the ongoing Phase 1/2a trial. These presentations will offer the scientific and medical communities a deeper look at the data supporting VO659 as it advances through the clinic, now on two continents. The combination of a more convenient dosing regimen and a clear regulatory path in the U.S. marks a period of significant momentum for the program.