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Enrolling by Invitation

NCT Number: NCT07537075

An Extension of SKY-0515 in Participants With Huntington's Disease

The goal of this clinical trial is to test if the drug SKY-0515, an oral medication, can lower harmful proteins linked to Huntington's Disease (HD) and improve the symptoms of participants with HD. This study includes men and women aged 25 and older who have HD confirmed by genetic testing and meet certain requirements for physical ability and independence.

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Key information

Conditions

Huntington's Disease (HD) Basal Ganglia Diseases Brain Diseases Central Nervous System Diseases Chorea Cognition Disorders Congenital, Hereditary, and Neonatal Diseases and Abnormalities Dementia Dyskinesias Genetic Diseases, Inborn Heredodegenerative Disorders, Nervous System Huntington Disease Mental Disorders Movement Disorders Nervous System Diseases Neurocognitive Disorders Neurodegenerative Diseases

Age range

25 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2 / Phase 3

Primary location

John Hunter Hospital, New Lambton Heights, New South Wales, Australia

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About this study

This is an OLE study to investigate the long-term safety, tolerability, and efficacy of SKY-0515 administered orally in participants with HD. To be eligible for this OLE study, participants must have completed dosing in a prior SKY-0515 treatment study and meet eligibility criteria for this study at an approved clinical study site. The study is comprised of an enrollment visit, a treatment period, and a follow-up visit. Throughout the study, participants will be evaluated as specified in the Schedule of Activities. At the enrollment visit (which may be the same as the last treatment visit of the prior study), participants will be consented to enter the OLE study and initiate open label treatment with 9 mg tablets of SKY-0515. Open label SKY-0515 will be self-administered daily (QD).

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Must have completed treatment in a prior SKY-0515 treatment study and, in the opinion of the Investigator, have been compliant with the prior SKY-0515 treatment protocol study procedures.
  • Must be able and willing to meet all study requirements in the opinion of the Investigator including:
  • Participants must be able to tolerate blood draws
  • Willing and able to comply with all scheduled visits, treatment plans,laboratory tests and other study procedures
  • Women who can have children must have a negative pregnancy test before starting and use two types of birth control during the study and for 30 days after the last dose of the study drug.
  • Men must agree to use birth control during the study and for 90 days after the last dose.

Exclusion criteria

-Have any other conditions that, in the opinion of the Investigator or Sponsor, would make the participant unsuitable for inclusion, or could interfere with the participant participating in or completing the study.

Treatment and study plan

SKY-0515

Drug

Study Drug Name (INN): SKY-0515 Type: Drug (small molecule) Dosage Level(s): 9mg Route of Administration: Oral Dosage Frequency: Once daily Treatment Duration: until drug becomes commercially available or until the development of SKY-0515 is terminated by the Sponsor. Use: Experimental Sourcing: SKY-0515 will be provided centrally by the Sponsor or subsidiary, or designee Packaging and Labeling: Study drug will be provided in bottles labeled as required per country requirement. All packaging and labeling operations for the study drug will be performed according to current Good Manufacturing Practice for Medicinal Products and the relevant regulatory requirements.

Primary outcomes

  1. Long-term safety and tolerability of SKY-0515

    Time frame: Continuously from enrollment to study completion or approximately 36 months

    To investigate the long-term safety and tolerability of SKY-0515 through the Incidence, severity, and relationship of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs) (including withdrawals due to TEAEs)

Secondary outcomes

  1. Change From Baseline in the Z-score from the Composite Unified Huntington's Disease Rating Scale (cUHDRS)

    Time frame: Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

    cUHDRS includes the Total Functional Capacity (range, 0-13; higher score means better functioning), Total Motor Score (range, 0-124; higher score means worse motor severity), Symbol Digit Modality Test (range, 0-110, correctly paired numbers-symbols in 90 seconds; higher score means better cognitive performance), and Stroop Color and Word Test (range, 0-no max value, correctly read color words in 45 seconds; higher score means better cognitive performance) scores. A z-score for each test is calculated, which alone can be used to describe relationship between an individual's test score and the mean score of a target population. A z-score of 0 is the mean, and ±1 is 1 standard deviation from the mean. For cUHDRS, z-scores of each test are summed, whereby a higher cUHDRS score is better (score of -3.06-no max value) and a change of ≥1.2 is a meaningful worsening, shown to track functional decline.

  2. Change from Baseline in Total Motor Score (TMS)

    Time frame: Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

    The total motor score (TMS) assessed motor features of HD with standardized ratings of oculomotor function, dysarthria, chorea, dystonia, gait, and postural stability. Some items (such as chorea and dystonia) required grading each extremity (face, bucco-oral-lingual, and trunk) separately. Eye movements require both horizontal and vertical grades. The total motor impairment scores was the sum of all the individual 31 motor sub-items (each rated from 0 to 4), with higher scores indicating more severe motor impairment than lower scores. The range of TMS is 0-124.

  3. Change from Baseline in Total Functional Capacity (TFC)

    Time frame: Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

    TFC consists of five ordinally scaled items assessing a person's capacity with: (1) occupation; (2) financial affairs; (3) domestic responsibilities; (4) activities of daily living; and (5) independent living. Total score ranges from zero (worst) to 13 (best).

  4. Change from Baseline in Independence Scale Score (IS)

    Time frame: Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

    The independence scale assesses independence on a 0 to 100 scale with higher scores indicating better functioning.

  5. Change from Baseline in Symbol Digit Modalities Test (SDMT)

    Time frame: Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

    The SDMT assesses attention, visuoperceptual processing, working memory, and cognitive/psychomotor speed. The score is the number of correctly paired abstract symbols and specific numbers in 90 seconds with higher scores indicating better cognitive functioning.

  6. Change from Baseline in the Stroop Color and Word Test (SCWT)

    Time frame: Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

    In the Stroop Color and Word Test (SCWT) the number of words and colors read correctly is counted, with a higher score indicating better cognitive performance scores. There is no upper limit for SWR as it is a time-based task. The lower limit (worst possible) however is 0; higher score is better meaning less severity.

Sponsors and collaborators

Lead sponsor

Skyhawk Therapeutics, Inc.

Industry

Registry information

Official study title

An Open Label Extension of SKY-0515 in Participants With Huntington's Disease Who Completed a Prior SKY-0515 Treatment Study

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Apr 17, 2026
Registry last updated
Jul 24, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

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This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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