Dose-Ranging Study of ST-920, an AAV2/6 Human Alpha Galactosidase A Gene Therapy in Subjects With Fabry Disease (STAAR)

Study Overview
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Brief Summary
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This is the first in human treatment with ST-920, a recombinant AAV2/6 vector encoding the cDNA for human a-Gal A. The purpose of this study is to evaluate the safety and tolerability of ascending doses of ST-920. ST-920 aims to provide stable, long-term production of α-Gal A at therapeutic levels in subjects with Fabry disease. The constant production of α-Gal A in humans should, importantly, enable reduction and potentially clearance of Fabry disease substrates Gb3 and lyso-Gb3. On Day 1, patients will be infused intravenously with a single dose of ST-920 and followed for a period of 52 weeks.

Official Title
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A Phase I/II, Multicenter, Open-Label, Single-Dose, Dose-Ranging Study to Assess the Safety and Tolerability of ST-920, an AAV2/6 Human Alpha Galactosidase A Gene Therapy, in Subjects With Fabry Disease (STAAR)

Conditions
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Fabry Disease

Intervention / Treatment
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* Biological: ST-920


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ≥ 18 years of age Documented diagnosis of Fabry disease One or more of the following symptoms: i) cornea verticillata, ii) acroparesthesia, iii) anhidrosis, iv) angiokeratoma Subject must be fully vaccinated (as per the Centers for Disease Control and Prevention (CDC) definition in the US and as per local guidelines in other countries) for COVID-19 at least one month prior to dosing Additional Inclusion Criteria: Renal Cohort: Screening eGFR value between 40-90 mL/min/1.73 m² Linear negative eGFR slope (estimated from at least 3 serum creatinine values within 18 months, including the value obtained during screening visit) of ≥ 2 mL/min/1.73m²/year Cardiac Cohort: • Left ventricular hypertrophy (LVH) in 2D echocardiography or CMR defined as an end diastolic septum and posterior wall thickness ≥12 mm with no other explanation for LVH, OR presentation with cardiac changes indicative of disease progression such as decreased global longitudinal strain on 2D strain echocardiography or low native T1 mapping on CMR Exclusion Criteria: Neutralizing antibodies to AAV6 eGFR < 40 ml/min/1.73m2 New York Heart Association Class III or higher Active infection with hepatitis A, B or C, HIV or TB History of liver disease such as clinically significant steatosis, fibrosis, non-alcoholic steatohepatitis (NASH) and cirrhosis, biliary disease within 6 months of informed consent; except for Gilbert's syndrome Elevated circulating serum AFP Recent or recurrent hypersensitivity response to ERT within within 6 months prior to consent Current or history of systemic (IV or oral) immunomodulatory agents, or biologics or steroid use in the past 6 months prior to consent (topical treatment and inhaled allowed). Contraindication to use of corticosteroids History of malignancy except for non-melanoma skin cancer and localized prostate cancer treated with curative intent Recent history of alcohol or substance abuse Participation in investigational interventional drug or medical device study throughout the duration of this study and within previous 3 months prior to consent Prior treatment with a gene therapy product Known hypersensitivity to components of ST-920 formulation Any other reason that, in the opinion of the Site Investigator or Medical Monitor, would render the subject unsuitable for participation in the study including but not limited to risk of COVID-19 infection Additional exclusion criteria for: Renal cohort: History of renal dialysis or transplantation History of acute kidney insufficiency in the 6 months prior to screening Angiotensin converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) therapy initiated within 4 weeks prior to screening or changed ACE inhibitor or ARB dose in the 4 weeks prior to screening Urine protein to creatinine ratio (UPCR) > 0.5 g/g who are not being treated with an ACE inhibitor or ARB Cardiac cohort: Significant cardiac fibrosis defined by late gadolinium enhancement on CMR Any contraindications to CMR as per local hospital/institution guidelines Angiotensin converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) therapy initiated within 4 weeks prior to screening or changed ACE inhibitor or ARB dose in the 4 weeks prior to screening NYHA Class IV

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Sequential Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sequential dose escalation<br>ST-920 is administered as a single infusion: Cohort 1: 0.5e13 vg/kg Cohort 2: 1.0e13 vg/kg Cohort 3: 3.0e13 vg/kg Cohort 4: 5.0e13 vg/kg | Biological: ST-920<br>* Single dose of investigational product ST-920<br>|
| Experimental: Expansion Cohorts<br>Anti Alpha-Gal A Antibody Positive Cohort Anti Alpha-Gal A Antibody Negative Cohort Female Cohort Renal Cohort Cardiac Cohort | Biological: ST-920<br>* Single dose of investigational product ST-920<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of treatment-emergent adverse events (TEAEs) | Incidence of Treatment-Emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs) in subjects who receive ST-920 as assessed by Common Terminology Criteria for Adverse Events (CTCAE) | Up to 12 months after the ST-920 infusion | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Rare, Lysosomal Storage Disease, Gene Therapy, Sangamo