SHIELD HD is an international, multisite, prospective, longitudinal cohort natural history study to assess the natural history of HD and its biomarkers that are associated with modulation of the number of cytosine-adenine-guanine (CAG) repeats in the mutant Huntingtin (HTT) gene.

Approximately 60 patients will be enrolled into the study and followed for up to 24 months at clinical sites in North America and Europe.

The results of this study will inform assessments for a future interventional treatment trial.

The rationale for this study is to obtain longitudinal information related to Somatic Instability and DNA damage response genes in HDGECs at various stages of the disease. Established assessments of disease progression will also be recorded.

Key Inclusion Criteria

Patients who meet all of the following criteria will be eligible to participate in the study:

1. Capacity to comprehend the study objectives and procedures
2. Documentation of genetically confirmed disease by direct DNA testing, defined as a CAG repeat length ≥39 in the HTT gene
3. Ability to undergo and tolerate MRI scans
4. Ability to tolerate blood draws and lumbar punctures

Key Exclusion Criteria

Patients who meet any of the following criteria will be excluded from participation in the study:

1. Any conditions, including severe chorea and dementia, that would prevent either writing or performing pen and paper, tablet, or computer based tasks as determined by the Investigator
2. Treatment with an investigational drug within 30 days prior to screening or within 5 half lives of the investigational drug, whichever is longer
3. History of gene therapy or cell transplantation or any other experimental brain surgery

Huntington disease (HD), genetically confirmed by direct DNA testing, either obtained previously or performed at Screening