Huntington's Study Group (HSG)

The Huntington’s Study Group (HSG) is a non-profit, peer-reviewed research consortium dedicated to conducting clinical trials to advance treatments for Huntington’s disease and related neurodegenerative disorders. Founded in 1993 in Rochester, New York, HSG has grown to become the world’s leading clinical research organization exclusively focused on Huntington’s disease, having conducted over 40 clinical trials—more than any other organization globally. The consortium’s work has been instrumental in developing three FDA-approved treatments for Huntington’s disease chorea and establishing the gold standard assessment tools used worldwide in HD clinical research.

History and Foundation

The Huntington’s Study Group was established in 1993 by a group of neurologists and researchers who recognized the critical need for a coordinated, multicenter approach to Huntington’s disease clinical research. Before HSG’s formation, clinical trials for Huntington’s disease were fragmented, with limited coordination between research centers and inconsistent outcome measures. The founding investigators aimed to create a network that could conduct rigorous, large-scale clinical trials with standardized protocols and validated outcome measures.

The organization was modeled after the Parkinson’s Study Group (PSG), which was established in 1985 and had demonstrated the success of academic clinical trial consortia in advancing treatments for neurodegenerative diseases. HSG expanded upon this model, creating a dedicated infrastructure for Huntington’s disease that has since become the template for similar efforts in other rare neurodegenerative disorders.

Pathway / Mechanism Diagram

graph TD
    A["HTT Gene: CAG Repeat Expansion"] --> B["Mutant Huntingtin (mHTT)"]
    B --> C["Polyglutamine Aggregation"]
    C --> D["Nuclear Inclusions"]
    B --> E["Transcriptional Dysregulation"]
    E --> F["BDNF Downregulation"]
    F --> G["Striatal Neuron Vulnerability"]
    B --> H["Mitochondrial Dysfunction"]
    H --> I["Energy Deficit"]
    B --> J["Impaired Autophagy"]
    J --> K["Toxic Protein Accumulation"]
    G --> L["Medium Spiny Neuron Death"]
    I --> L
    K --> L
    L --> M["Chorea and Motor Symptoms"]
    L --> N["Cognitive Decline"]
    L --> O["Psychiatric Symptoms"]
    style A fill:#ef5350,color:#e0e0e0
    style L fill:#ef5350,color:#e0e0e0
    style B fill:#5d4400,color:#e0e0e0

Mission and Goals

The HSG’s mission is to accelerate treatments that make a difference for Huntington’s disease through research, education, and collaboration. The organization is dedicated to improving quality of life and outcomes for those impacted by Huntington’s disease by:

• Conducting high-quality clinical trials that meet rigorous scientific and regulatory standards

• Developing and validating outcome measures that accurately capture disease progression and treatment effects

• Training the next generation of Huntington’s disease clinical researchers

• Facilitating collaboration between academic centers, pharmaceutical companies, patient advocacy groups, and regulatory agencies

• Advancing disease understanding through observational studies and clinical research

Organizational Structure

HSG operates through a dual structure that combines the non-profit research consortium with a for-profit Contract Research Organization (CRO):

HSG Clinical Research, Inc

HSG Clinical Research, Inc. is a wholly owned for-profit subsidiary that serves as the only CRO dedicated exclusively to Huntington’s disease trials. This entity provides comprehensive clinical trial management services including protocol development, site recruitment, data management, regulatory affairs, and biostatistics. The dual structure allows HSG to maintain academic rigor while operating with the efficiency and flexibility of a commercial CRO.

Executive Leadership

The organization is governed by a Board of Directors composed of leading Huntington’s disease researchers, patient advocates, and industry representatives. A Scientific Advisory Board provides oversight and guidance on research priorities.

Member Sites

HSG’s network includes over 200 credentialed clinical trial sites across North America, Europe, Australia, and other regions. Each site must meet strict quality standards and demonstrate expertise in Huntington’s disease clinical research.

Research Focus Areas

The HSG focuses exclusively on Huntington’s disease clinical research across multiple therapeutic domains:

Symptomatic Treatments

HSG has been pivotal in developing medications to manage Huntington’s disease symptoms:

• Chorea Management: The organization led clinical trials for all three FDA-approved drugs for Huntington’s disease chorea:

  • Tetrabenazine (Xenazine): The first FDA-approved treatment for HD chorea, approved in 2008

  • Deutetrabenazine (Austedo): Approved in 2017, offering improved tolerability

  • Valbenazine (Ingrezza): Approved in 2023, providing long-acting symptom control

• Motor Symptoms: Beyond chorea, HSG researches treatments for dystonia, bradykinesia, and gait disturbances

• Cognitive Symptoms: Interventions for executive dysfunction, memory deficits, and processing speed impairment

• Psychiatric Symptoms: Treatments for depression, anxiety, irritability, and psychosis

Disease-Modifying Therapies

HSG leads trials targeting the underlying disease process:

• Huntingtin-Lowering Approaches: ASO therapies that reduce mutant huntingtin protein production

  • Tominersen: Roche’s ASO, previously in Phase 3 GENERATION-HD1 trial

  • PTC518: PTC Therapeutics’ ASO, showing promising results in Phase 2

  • AMT-130: uniQure’s gene therapy approach

• Neuroprotective Agents: Compounds aimed at protecting neurons from degeneration

• Gene Therapy Approaches: Novel vectors and delivery systems for targeted gene modulation

Novel Therapeutic Approaches

• Antisense Oligonucleotide (ASO) Therapies: Small RNA molecules that selectively reduce mutant huntingtin expression

• RNAi-Based Therapies: Gene silencing approaches using RNA interference mechanisms

• Small Molecule Modulators: Drug candidates targeting specific pathogenic pathways

• Cell-Based Therapies: Stem cell and regenerative medicine approaches

Clinical Trial Network

The HSG operates as the world’s largest Huntington’s disease clinical research network with credentialed trial sites worldwide. This network provides:

Site Network Capabilities

• Rapid Patient Recruitment: Access to over 15,000 enrolled patients in Enroll-HD

• Experienced Investigators: Trained neurologists, psychiatrists, and neuropsychologists

• Comprehensive Assessments: Full capabilities for motor, cognitive, behavioral, and functional evaluations

• Regulatory Expertise: Established relationships with FDA, EMA, and other regulatory bodies

Clinical Trial Phases

HSG supports trials across all phases:

• Phase 1: First-in-human safety and tolerability studies

• Phase 2: Dose-finding and preliminary efficacy

• Phase 3: Pivotal registration trials

• Phase 4: Post-marketing surveillance and optimization

Landmark Clinical Trials

The HSG has contributed to numerous landmark clinical trials that have shaped Huntington’s disease treatment:

FDA-Approved Treatments

1. Tetrabenazine Trials: Led to first FDA approval for HD chorea in 2008

2. DEUXET Trial: Demonstrated efficacy of deutetrabenazine, leading to 2017 approval

3. KINECT-HD Trial: Established valbenazine as third FDA-approved chorea treatment

Disease-Modifying Trials

4. GENERATION-HD1 (Tominersen): Large Phase 3 trial huntingtin-lowering therapy

5. PTC518 Clinical Program: Phase 2 study showing dose-dependent huntingtin reduction

6. AMT-130 (uniQure): First gene therapy trial for Huntington’s disease

Observational Studies

7. Enroll-HD: The world’s largest Huntington’s disease observational study, with over 15,000 participants across 15 countries. This longitudinal study provides invaluable data on disease progression, biomarkers, and natural history.

Key Contributions to Huntington’s Disease Research

Unified Huntington’s Disease Rating Scale (UHDRS®)

The HSG developed and validated the Unified Huntington’s Disease Rating Scale (UHDRS®), an invaluable research tool that provides a uniform assessment of the clinical features and course of HD. First published in 1996, the UHDRS comprises four major components:

• Motor Assessment: Standardized evaluation of chorea, dystonia, bradykinesia, gait, and other movement abnormalities

• Cognitive Assessment: Battery of neuropsychological tests evaluating executive function, memory, and processing speed

• Behavioral Assessment: Quantification of psychiatric symptoms including depression, anxiety, irritability, and psychosis

• Functional Assessment: Evaluation of daily living activities, occupational functioning, and level of care required

The UHDRS has become the gold standard for clinical trials and disease monitoring, with over 1,300 PubMed publications citing its use^{1PubMed Search - Huntington's Study GroupOpen reference}. The scale’s reliability and consistency were validated in the foundational HSG publication (PMID: 8684382)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}.

First FDA-Approved Treatments

HSG-led trials resulted in the three FDA-approved drugs for Huntington’s disease chorea:

Non-Motor Diagnostic Criteria

HSG’s Neuropsychology Working Group has been instrumental in implementing non-motor diagnostic criteria for Huntington’s disease, published in 2023 (PMID: 38094638)^{3Huntington Study Group's Neuropsychology Working Group: Implementing Non-Motor Diagnostic CriteriaOpen reference}. This work addresses the increasingly recognized importance of cognitive and psychiatric symptoms in disease diagnosis and monitoring.

Current Studies and Pipeline

HSG continues to lead important clinical studies across the therapeutic pipeline:

Active Clinical Trials

• Burden of HD Chorea: Characterizing the impact of chorea on quality of life and functional abilities

• LEAD-HD: Longitudinal evaluation of motor phenotype characterization

• SPK-10001-101: Gene therapy trials for Huntington’s disease

Drug Development Pipeline

The Huntington’s disease therapeutic pipeline is robust, with multiple programs in various stages of development:

The HSG Clinical Trials Corner provides regular updates on these programs (PMID: 38489195)^{4Huntington's Disease Clinical Trials Corner: March 2024Open reference}, (PMID: 39973379)^{5Huntington's Disease Clinical Trials Update: September 2024Open reference}.

Research Publications and Scientific Contributions

HSG investigators have authored over 1,300 publications on Huntington’s disease research, spanning basic science, clinical trials, and outcomes research. Key publication themes include:

Disease Mechanisms

• Molecular pathogenesis and huntingtin protein biology (PMID: 22187252)^{6Huntington's disease: new insights into molecular pathogenesisOpen reference}

• Genetics and neurobiology of Huntington’s disease (PMID: 29607608)^{7Huntington disease: genetics and neurobiologyOpen reference}

• Unified dual pathogenetic model (PMID: 33248141)^{8Huntington's disease: a unified dual pathogenetic modelOpen reference}

Therapeutic Development

• Huntingtin-lowering therapies (PMID: 25030796)^{9Huntingtin-lowering therapy in Huntington diseaseOpen reference}

• ASO gene silencing approaches (PMID: 39024687)^{10ASO gene silencing therapies for Huntington's diseaseOpen reference}

• Molecular therapy advances (PMID: 39024688)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}0

• Drug development pipeline analysis (PMID: 34551948)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}1

• New therapeutic strategies (PMID: 34054910)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}2

Clinical Outcomes

• Wearable sensor monitoring (PMID: 31868675)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}3

• Quality of life and caregiver burden (PMID: 36084356)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}4

• Cognitive trajectory studies (PMID: 36994811)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}5

• Non-motor phenotype characterization (PMID: 37199368)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}6

• Biomarker development (PMID: 37565221)^{2Unified Huntington's Disease Rating Scale: reliability and consistencyOpen reference}7

Collaboration and Partnerships

Patient Advocacy Organizations

HSG collaborates closely with Huntington’s disease patient advocacy organizations:

• CHDI Foundation: A nonprofit pharmaceutical company dedicated to accelerating therapies for Huntington’s disease

• Hereditary Disease Foundation: Founded by Milton Wexler, supporting HD research since 1968

• Huntington’s Disease Society of America (HDSA): Patient advocacy and support organization

International Networks

• European Huntington’s Disease Network (EHDN): European counterpart to HSG

• International Parkinson’s Disease Genomics Consortium: Collaboration on overlapping neurodegenerative mechanisms

• Michael J. Fox Foundation for Parkinson’s Research: Joint funding initiatives

Academic Consortia

• Parkinson’s Study Group: Founded 1985, similar model to HSG

• ALS Clinical Trials Consortium: Sharing methodological expertise

Training and Education

HSG is committed to training the next generation of Huntington’s disease researchers:

Investigator Training Programs

• Clinical trial methodology workshops

• UHDRS certification training

• Good Clinical Practice (GCP) certification

• Regulatory affairs training

Fellowship Opportunities

• Postdoctoral fellowships in Huntington’s disease clinical research

• Clinical research coordinator training

• Clinical trial design courses

Patient and Family Education

• Annual Meeting educational sessions

• Webinars on new research findings

• Clinical trial awareness programs

Impact and Achievements

Impact on Drug Development

HSG has fundamentally shaped Huntington’s disease drug development through its coordinated approach:

Accelerated Timeline: By providing a unified network for clinical trials, HSG has significantly reduced the time required to advance therapeutic candidates from preclinical to clinical stages. The consortium’s infrastructure enables rapid patient recruitment and data collection that would be impossible for individual centers.

Regulatory Engagement: HSG maintains active relationships with regulatory agencies including FDA and EMA, providing guidance on clinical trial design for Huntington’s disease. This engagement has been crucial in establishing regulatory precedent for novel therapeutic endpoints and trial designs.

Standardization: The development and adoption of UHDRS as the standard outcome measure has enabled cross-trial comparisons and meta-analyses that would not be possible with heterogeneous assessment approaches.

Economic Impact

The economic impact of HSG’s work extends beyond direct therapeutic development:

• Reduced clinical trial costs through coordinated site networks

• Creation of specialized Huntington’s disease research infrastructure

• Training of clinical researchers who contribute to the broader neurodegenerative disease research ecosystem

• Generated intellectual property and technology transfer from academic discoveries

• Healthcare cost savings from earlier diagnosis and intervention

• Reduced burden on caregivers through development of effective treatments

Industry Partnerships

HSG has established productive relationships with pharmaceutical and biotechnology companies:

• Roche/Genentech: Collaboration on tominersen and other huntingtin-lowering therapies

• PTC Therapeutics: Partnership for PTC518 clinical development

• uniQure: Collaboration on AMT-130 gene therapy trials

• VICO Therapeutics: Early-stage ASO program support

• Wave Life Sciences: Partnership for WVE-003 development

These partnerships enable efficient translation of academic discoveries into clinical applications while maintaining scientific rigor and patient safety.

Global Health Impact

Underserved Populations

HSG has made significant efforts to include underrepresented populations in clinical research:

• Expansion of site network to include centers in Latin America, Asia, and Africa

• Development of culturally appropriate education materials

• Translation of consent forms and study documents

• Engagement with patient advocacy groups representing diverse communities

Healthcare Provider Training

Beyond clinical trials, HSG contributes to broader healthcare provider education:

• Development of clinical practice guidelines for Huntington’s disease management

• Continuing medical education programs

• Resources for genetic counselors and care coordinators

• Support for multidisciplinary care team development

Relationship to Parkinson’s Study Group

The HSG was founded in 1993, eight years after the Parkinson’s Study Group (PSG) was established in 1985. Both organizations follow similar models of academic clinical trial consortia and share several methodological and operational approaches. The two organizations occasionally collaborate on research involving overlapping neurodegenerative mechanisms, particularly given the growing recognition of shared pathological pathways between Huntington’s and Parkinson’s diseases.

Lessons Learned from PSG Model

HSG adapted several key elements from the Parkinson’s Study Group model:

• Multi-center collaborative research structure

• Standardized assessment protocols

• Industry partnership frameworks

• Data sharing and governance policies

• Training and career development programs

Future Directions

HSG’s strategic priorities for coming years include:

Precision Medicine Initiatives

• Genetic subtyping and targeted therapy approaches

• Biomarker-driven patient selection for clinical trials

• Individualized treatment response prediction

Digital Health Integration

• Remote monitoring and telehealth capabilities

• Digital biomarker development

• Wearable device integration

Global Expansion

• Increased representation in Asia and Latin America

• Enhanced diversity in clinical trial populations

• Standardized global data collection

Novel Trial Designs

• Platform trials for efficient multiple-arm studies

• Master protocols for rapid therapy evaluation

• Adaptive designs for optimized dosing

Cross-Links

Related pages in NeuroWiki:

• Huntington’s Disease

• Huntington’s Disease Clinical Trials

• CHDI Foundation

• Hereditary Disease Foundation

• Parkinson’s Study Group

• European Huntington’s Disease Network

• Tetrabenazine

• Deutetrabenazine

• Valbenazine

• Tominersen

See Also

• Huntington’s Disease

• Huntington’s Disease Clinical Trials

• CHDI Foundation

• Hereditary Disease Foundation

• Parkinson’s Study Group

External Links

• HSG Official Website

• HSG Clinical Research

• Enroll-HD Study

• UHDRS Information

• PubMed Publications