Huntington Disease (HD) Clinical Trials and Treatments

Huntington disease (HD) is an autosomal dominant neurodegenerative disorder caused by expansion of a CAG trinucleotide repeat in the HTT (huntingtin) gene. A CAG repeat count of 40 or higher confirms HD, while 36-39 repeats indicate reduced penetrance. The number of CAG repeats correlates inversely with age of onset, with longer repeats causing earlier disease.

The most common symptoms of Huntington Disease include Involuntary movements (chorea), especially in arms and face, Slow, jerky movements or dystonia, Rigidity and muscle weakness, Cognitive decline and difficulty concentrating, Irritability, mood changes, and depression, among others. Huntington Disease affects approximately 5-10 per 100,000 people of European descent; lower in other populations. Symptoms can range from mild to severe and may vary between individuals.

Trial Friend lists all active clinical trials for Huntington Disease from ClinicalTrials.gov, with eligibility criteria translated into plain English. Patients can filter by trial phase and recruitment status, search by location, and use the Match Me tool to score trials against their profile. Huntington disease research is advancing 3 distinct approaches to lower mutant huntingtin levels. Antisense oligonucleotides (ASOs) like tominersen reduce HTT mRNA through intrathecal injection.

Yes. As of September 2026, Trial Friend lists 3 FDA-approved drugs used to treat Huntington Disease: Xenazine (tetrabenazine), first approved in 2008; Austedo (deutetrabenazine), first approved in 2017; and Ingrezza (valbenazine), first approved in 2023.

Each has its own page with what the label covers, side effects and how it is given, and the Treatments section of this page adds any further approved drugs found in FDA labeling data.

Huntington disease is caused by an expanded CAG repeat in the HTT gene, which produces a mutant huntingtin protein with an abnormally long polyglutamine stretch. This mutant protein misfolds, aggregates, and forms toxic intranuclear inclusions that damage medium spiny neurons in the striatum (caudate and putamen) first, then spread to cortical and other brain regions. The striatum coordinates voluntary movement, which is why chorea (involuntary jerking movements) is a hallmark early symptom. Progressive damage to frontal cortex circuits causes cognitive decline and executive dysfunction, while damage to limbic circuits contributes to psychiatric symptoms like depression, irritability, and apathy. Somatic CAG repeat expansion (the repeat getting longer in brain cells over time) is now recognized as a key driver of disease progression and is a target of several experimental therapies.

Huntington disease is caused by a CAG trinucleotide repeat expansion in the HTT gene on chromosome 4. Genetic testing is a definitive diagnostic tool: 40 or more CAG repeats confirm HD, 36-39 repeats indicate reduced penetrance (may or may not develop symptoms), and 27-35 repeats are in the intermediate range (not affected but may expand in future generations). Most clinical trials require confirmed CAG repeat count of 36 or higher, with many gene-silencing trials requiring 40+. Predictive testing is available for at-risk family members through certified genetic counselors. The decision to undergo presymptomatic testing is deeply personal and should include genetic counseling before and after. Labs offering HTT testing include GeneDx, Invitae, and Quest Diagnostics.

Eligibility for Huntington Disease clinical trials depends on factors like age, diagnosis, treatment history, and overall health. Each trial sets its own inclusion and exclusion criteria. Trial Friend translates these requirements from medical language into plain English so patients can review them more easily. The Match Me tool can score your profile against active trials to help identify studies that may be a fit.

Participating in a Huntington Disease clinical trial typically involves scheduled visits, medical tests, and close monitoring by a research team. Depending on the study phase, you may receive an investigational treatment, a placebo, or the current standard of care. Trials may last from a few weeks to several years. Study participation is voluntary, and you can withdraw at any time.

Huntington disease clinical trials commonly exclude specific CYP2D6 inhibitors (fluoxetine, paroxetine, bupropion) when the experimental drug is metabolized by that enzyme, QT-prolonging medication combinations, MAOIs, and antipsychotic polypharmacy. Prior exposure to gene-silencing therapies (tominersen, AMT-130) may exclude you from new trials in the same class. Trial Friend's medication conflict checker scans each trial's exclusion criteria against common HD medications including VMAT2 inhibitors, antipsychotics, antidepressants, benzodiazepines, mood stabilizers, and investigational agents. The checker flags the specific drug, the trial's exclusion language, and a confidence level so you can discuss options with your neurologist.

Key questions to ask your neurologist about HD clinical trials include: Are there gene-silencing trials (ASOs, siRNA, or splicing modifiers) enrolling for my CAG repeat length and disease stage? Would I need to stop my VMAT2 inhibitor or antipsychotic before joining a trial? I take fluoxetine (or paroxetine or bupropion) for depression. Is that a CYP2D6 issue and could I switch to a different antidepressant to open up more trial options? Are there prevention trials for premanifest gene carriers? What is my current Total Functional Capacity (TFC) score and cognitive status, and which trials match my disease stage? If I was in a previous gene therapy or ASO trial, am I excluded from all new HTT-lowering studies?