Safety and Tolerability Study of ST-503 for Refractory Pain Due to Peripheral Neuropathy (Small Fiber Predominant, SFN)

May 28, 2026 updated by: Sangamo Therapeutics

A Multicenter Phase 1 / 2 Double-blind, Randomized, Sham-controlled Dose Escalation Study to Determine Safety and Tolerability of Single Dose Intrathecal ST-503 Gene Therapy for Refractory Pain Due to Peripheral Neuropathy (Small Fiber Predominant, SFN)

This research is being done to study a possible treatment for refractory pain due to small fiber neuropathy (SFN).

ST-503 is intended to deliver a modified copy of the gene which will ideally repress Nav1.7 tissue-related pain signals reaching the brain, which should reduce the refractory pain due to small fiber neuropathy (SFN).

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This research is being done to study a possible treatment for refractory pain due to small fiber neuropathy (SFN).

Small fiber neuropathy happens when something damages small nerve fibers in your skin, causing symptoms like painful tingling or burning sensations in your hands and feet. Pain originating in the nerves outside of the brain and spinal cord is defined by doctors as neuropathic pain. Scientists have discovered that certain proteins in our bodies called sodium channels are important for communicating pain signals in nerves, specifically, Nav1.7, Nav1.8 and Nav1.9. This first-in-human study will test the use of a type of experimental treatment called "gene therapy." The primary goal is to determine if it is safe and well tolerated. The second goal is to determine if it reduces the level of refractory pain due to SFN disease. The gene will be delivered into your cells using a special delivery tool called a vector.

Study Type

Interventional

Enrollment (Estimated)

27

Phase

  • Phase 2
  • Phase 1

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 Locations

  • United States
    • Arizona
    • Arkansas
      • Little Rock, Arkansas, United States, 72205
    • California
      • La Jolla, California, United States, 92093
        • Not yet recruiting
        • The University of California, San Diego
    • Maryland
      • Baltimore, Maryland, United States, 21218
        • Recruiting
        • Johns Hopkins University
        • Contact:
    • Massachusetts
      • Boston, Massachusetts, United States, 02114
    • New Hampshire
      • Lebanon, New Hampshire, United States, 03766
        • Not yet recruiting
        • Dartmouth Hitchcock Medical Center
    • New York
      • New York, New York, United States, 10027
        • Recruiting
        • Columbia University Irving Medical Center (CUIMC) and New York-Presbyterian Hospital (NYPH)
        • Contact:
    • North Carolina
      • Chapel Hill, North Carolina, United States, 27514
        • Not yet recruiting
        • University of North Carolina Medical Center
    • Tennessee
      • Nashville, Tennessee, United States, 37235
        • Not yet recruiting
        • Vanderbilt University
    • Utah
      • Salt Lake City, Utah, United States, 84112
        • Not yet recruiting
        • University of Utah
    • Virginia
      • Richmond, Virginia, United States, 23284

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

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria

  1. Diagnostic characterization of Small Fiber Neuropathy (SFN) according to the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities and Networks (ACTTION) criteria.
  2. Medical record documentation that pain is refractory to 2 of 3 categories of first line medical therapy for at ≥ 6 months prior to screening.
  3. Serum sample negative for pre-existing anti-AAV9 antibodies determined by assay detection limit

Exclusion Criteria

  1. Drug- and alcohol-related:

    1. Persons using opioid analgesics for under 3 months or persons who are not on a stable dose of opioids; if on a stable dose, the dose may decrease over the course of the study but should not be increased.
    2. History of known alcohol abuse, opioid analgesic abuse, or illicit drug abuse within 2 years of Screening.
    3. Positive urine test for drugs of abuse (including opiates, benzodiazepines, amphetamines, cocaine, barbiturates, and phencyclidine) without prescription and investigator approval, at Screening and Day -1.
    4. Use of cannabinoids is not permitted.
  2. Persons with Fabry's disease, with erythromelalgia, with peripheral neuropathies due to alcohol or drug toxicity, or with diagnosed channelopathies

  3. Procedure-related:

    1. Contraindications to LP, general anesthesia or sedation
    2. Any medical disorders that, in the opinion of the Investigator, could interfere with LP including but not limited to evidence for a pressure gradient between supratentorial and infratentorial compartments, Arnold-Chiari malformation, bleeding diathesis, clinically significant coagulopathy, thrombocytopenia, increased intracranial pressure, or spine disease or past surgical procedures involving the spine

  4. Infectious disease-related:

    1. Active viral infection or bacterial
    2. A severe infection (e.g., pneumonia, septicemia, central nervous system infections [e.g., meningitis, encephalitis]) within 12 weeks prior to Screening

  5. Hepatic disease- and hepatotoxic medication-related:

    1. Presence of clinically relevant liver disease
    2. Hepatic dysfunction as indicated by one or more of the following: i. Albumin ≤ 3.5 g/dL ii. Total bilirubin > 1.5 x ULN and direct bilirubin ≥0.5 mg/dL iii. Alkaline phosphatase (ALP) > 2 x ULN iv. Alanine transaminase (ALT) or aspartate transaminase (AST) > 1.5 x ULN
    3. Hepatotoxic medications should be avoided during the study period including acetaminophen exceeding 4 gm/day unless essential to patient's treatment, approved by investigator, and hepatic dysfunction is not identified
    4. Hepatotoxic supplement use during the study period

  6. Cancer-related:

    a. History of cancer, including B-cell cancers, within 5 years of Screening

    i. Exceptions to this exclusion are fully excised non-melanoma skin cancers, non-metastatic prostate cancer, and fully treated ductal carcinoma in situ of the breast, provided subject has been stable for at least 6 months

    b. Previous autologous or allogeneic bone marrow transplant, peripheral stem cell transplant or solid organ transplantation

  7. Previously received gene or cellular therapy

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: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Sham Comparator: Sham Controlled Study
Procedure: Sham (No Treatment)
Sham Procedure
Experimental: Investigational Agent
Genetic: ST-503
Genomic Medicine

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence and severity of treatment emergent adverse events (TEAEs)
Time Frame: 12 weeks
To assess safety and tolerability of ST-503 over a 12-week post-dosing observation period.
12 weeks

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Percentage of subjects with pain intensity reduction from baseline at Week 12
Time Frame: 12 weeks
  • 30% in the weekly average of daily pain intensity measurements performed using the PI-NRS

  • 50% in the weekly average of daily pain intensity measurements performed using the PI-NRS

    • Dose of rescue medication use
    • Frequency of rescue medication use
12 weeks
Percentage of subjects at Week 12
Time Frame: 12 weeks
  • Categorized as improved on the patient global impression of change (PGIC) assessment
  • With a ≥ 1-point improvement in suicidal ideation in Columbia Suicide Severity Rating Scale (C-SSRS) responses
12 weeks
Columbia Suicide Severity Rating Scale (CSSRS) Rating
Time Frame: 12 weeks
With a ≥ 1-point decline in suicidal ideation in Columbia Suicide Severity Rating Scale (CSSRS) responses
12 weeks
Overall Pain Intensity Numerical Rating Scale (PI-NRS) score
Time Frame: 12 Weeks
Participants will rate their pain intensity using an 11-point Numerical Rating Scale (0=no pain and 10=worst possible pain) and record their score in an electronic diary.
12 Weeks
Short Form McGill Pain Questionnaire-2 (SF-MQ-2)
Time Frame: 12 Weeks
This pain scale was developed to evaluate chronic neuropathic and non-neuropathic pain in adults. It consists of 22 descriptors of pain in 4 parts (continuous, intermittent, neuropathic, and affective pain types) to be rated from 0-10 with 0 indicating no pain and 10 the worst pain ever during the past week.
12 Weeks
Daily Sleep Interference Score (DSIS)
Time Frame: 12 Weeks
DSIS is assessed on an 11-point NRS, which ranges from 0 (none) to 10 (severe).
12 Weeks
Hospital Anxiety and Depression Scale (HADS)
Time Frame: 12 Weeks
HADS is a screening tool for anxiety and depression in non-psychiatric clinical populations consisting of 14 items (seven each for anxiety and depression). Higher scores correlate with worse symptoms.
12 Weeks
Rasch-Transformed 13-item SFN Symptoms Inventory Questionnaire
Time Frame: 12 Weeks
The 13-item SFN-SIQ evaluates changes in physiological functions such as sweating patterns and incontinence using a four-point Likert scale (0 = never present, 1 = sometimes, 2 = often, and 3 = always present) to get a sum of the grading scores attributed to each of the 13 items with a 0 to 39 range. Higher scores correlate with worse symptoms.
12 Weeks
SFN-specific Rasch-built Overall Disability Scale (SFN-RODS)
Time Frame: 12 Weeks
The 32-item SFN-RODS is a disease-specific interval measure suitable to detect activity limitations and participation restrictions in patients with SFN. The scale ranges from 0 to 64 with higher numbers indicating worse disability.
12 Weeks
36-Item Short Form Health Survey (SF-36) domains and summary scores
Time Frame: 12 Weeks
This measures quality of life measures such as physical functioning, emotional well-being, energy levels, and social functioning. The range is from 0-100 with higher scores being associated with a better perceived quality of life.
12 Weeks
Pain Catastrophizing Questionnaire (PCS)
Time Frame: 12 Weeks
PCS has 13 questions related to rumination, magnification and helplessness with values ranging 0 to 4 for a total possible score of 52. The higher the score the more pain catastrophizing is present.
12 Weeks

Collaborators and Investigators

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

Sponsor

Sangamo Therapeutics

Investigators

  • Study Director: Medical Monitor, Sangamo Therapeutics Inc.

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)

December 4, 2025

Primary Completion (Estimated)

July 1, 2027

Study Completion (Estimated)

July 1, 2028

Study Registration Dates

First Submitted

April 30, 2025

First Submitted That Met QC Criteria

May 12, 2025

First Posted (Actual)

May 20, 2025

Study Record Updates

Last Update Posted (Actual)

June 1, 2026

Last Update Submitted That Met QC Criteria

May 28, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ST-503-101

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

Yes

Studies a U.S. FDA-regulated device product

Yes

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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