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

July 23, 2026 updated by: Skyhawk Therapeutics, Inc.

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

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Enrolling by invitation

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

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).

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
500

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Australia
    • New South Wales
      • New Lambton Heights, New South Wales, Australia, 2305
        • John Hunter Hospital
      • Westmead, New South Wales, Australia, 2145
        • Westmead Hospital
    • Queensland
      • Herston, Queensland, Australia, 4006
        • The University of Queensland
    • South Australia
      • Adelaide, South Australia, Australia, 5042
        • Flinders Medical Centre
    • Victoria
      • Caulfield South, Victoria, Australia, 3162
        • Calvary Health Care Bethlehem
      • Parkville, Victoria, Australia, 3050
        • The Royal Melbourne Hospital
    • Western Australia
      • Nedlands, Western Australia, Australia, 6009
        • The Perron Institute for Neurology and Translational Science (Perron Institute)
  • New Zealand
      • Auckland, New Zealand, 0604
        • Huntington's Disease Association
      • Christchurch, New Zealand, 8011
        • New Zealand Brain and Research Institute
      • Wellington, New Zealand, 6021
        • Wellington Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

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.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: 9mg dose
Drug: SKY-0515 Type: Small molecule Route of Administration: Oral Dosage Frequency: Once daily Duration: until study drug is approved or study is discontinued Use: Experimental
Drug: SKY-0515
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.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
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)
Continuously from enrollment to study completion or approximately 36 months

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
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.
Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.
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.
Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.
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).
Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.
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.
Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.
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.
Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.
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.
Every 3 months for the first year, beginning with enrollment, then every six months for approximately 36 months.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Skyhawk Therapeutics, Inc.

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
April 10, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 1, 2029

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 1, 2029

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
April 3, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 15, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
April 17, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 24, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 23, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • SKY-0515-008

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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