#1 Clinical Trials Search in Europe

Adeno-Associated Viral Vector Serotype 8 Containing The Human Cnga3 Gene Under The Control Of A Cone Arrestin Promoter

A groundbreaking clinical trial is underway to investigate the safety and effectiveness of a new gene therapy treatment for CNGA3-linked achromatopsia, a rare genetic eye disorder. The study, named “Colour Bridge,” focuses on the use of rAAV.hCNGA3, an adeno-associated viral vector containing the human CNGA3 gene. This treatment is administered through a single subretinal injection in both eyes of adult and minor patients. The trial aims to evaluate how this innovative approach may potentially improve vision in individuals with this specific form of color blindness.

Table of Contents

What is rAAV.hCNGA3?

rAAV.hCNGA3 is an innovative medical treatment being studied for a rare eye condition called CNGA3-linked achromatopsia. This treatment is also known by its full scientific name: adeno-associated viral vector serotype 8 containing the human CNGA3 gene under the control of a cone arrestin promoter[1]. Let’s break down what this means:

  • Adeno-associated viral vector (AAV): This is a harmless virus that scientists have modified to deliver genetic material into cells.
  • Serotype 8: This refers to a specific type of the AAV that is particularly good at targeting eye cells.
  • Human CNGA3 gene: This is the gene that, when faulty, causes CNGA3-linked achromatopsia. The treatment carries a healthy version of this gene.
  • Cone arrestin promoter: This is a genetic “switch” that ensures the CNGA3 gene is activated in the right cells (cone cells) in the retina.

Target Condition: CNGA3-linked Achromatopsia

CNGA3-linked achromatopsia is a rare genetic eye disorder that affects the cone cells in the retina[1]. People with this condition have:

  • Complete color blindness (inability to see colors)
  • Very poor visual acuity (sharpness of vision)
  • Extreme sensitivity to light (photophobia)
  • Involuntary eye movements (nystagmus)

This condition is caused by mutations in the CNGA3 gene, which is essential for the proper functioning of cone cells in the retina.

How rAAV.hCNGA3 Works

rAAV.hCNGA3 is designed to treat CNGA3-linked achromatopsia by delivering a healthy copy of the CNGA3 gene directly to the cone cells in the retina[1]. Here’s how it works:

  1. The treatment is injected into the space under the retina (subretinal space).
  2. The viral vector enters the cone cells.
  3. The healthy CNGA3 gene is released into the cells.
  4. The cells begin to produce the correct protein, potentially restoring some function to the cone cells.

The goal is to improve visual function, including color vision and visual acuity, in people with this condition.

Clinical Trial: The Colour Bridge Study

rAAV.hCNGA3 is currently being tested in a clinical trial called “Colour Bridge”[1]. This study aims to evaluate the safety and effectiveness of the treatment in both adults and children with CNGA3-linked achromatopsia. Key features of the trial include:

  • It’s a randomized, wait-list controlled, observer-masked trial.
  • Participants receive a single injection of rAAV.hCNGA3 in both eyes.
  • The study includes both adults (18 years and older) and children (6-12 years old).

Who Can Participate in the Trial?

The trial has specific criteria for who can participate[1]. Some key inclusion criteria are:

  • Clinical diagnosis of achromatopsia
  • Confirmed bi-allelic (affecting both copies) pathogenic mutation in the CNGA3 gene
  • Age 6-12 years or ≥18 years
  • Minimum thickness of the outer nuclear layer of the retina

There are also several exclusion criteria, such as other eye diseases, certain systemic conditions, and recent eye surgeries.

Trial Objectives and Measurements

The main goal of the trial is to assess the safety and efficacy of rAAV.hCNGA3[1]. Researchers will measure:

  • Contrast sensitivity: The ability to distinguish between different levels of light and dark.
  • Visual acuity: The sharpness or clarity of vision.
  • Patient-reported outcomes: How patients feel the treatment has affected their vision and quality of life.
  • Electroretinography: A test that measures the electrical responses of various cell types in the retina.

How is rAAV.hCNGA3 Administered?

rAAV.hCNGA3 is given as a solution for injection[1]. It is administered through a procedure called a subretinal injection, which means it’s injected into the space under the retina. This is typically done under general anesthesia, especially for younger patients.

Potential Benefits and Considerations

While the potential benefits of rAAV.hCNGA3 are promising, it’s important to remember that this treatment is still experimental[1]. Possible benefits could include improved color vision, better visual acuity, and reduced light sensitivity. However, as with any medical treatment, there may be risks and side effects that are still being evaluated in the clinical trial.

Participants in the trial will need to use contraception for six months after treatment, indicating that the effects of the treatment on pregnancy are not yet known[1].

If you or a loved one has CNGA3-linked achromatopsia and are interested in this treatment, it’s crucial to discuss it with an eye care specialist who is familiar with genetic eye disorders. They can provide more information about the current status of this treatment and whether it might be appropriate for your specific situation.

Aspect Details
Study Name Colour Bridge
Condition CNGA3-linked achromatopsia
Treatment rAAV.hCNGA3 (Adeno-associated viral vector serotype 8 containing the human CNGA3 gene)
Administration Bilateral single subretinal injection
Age Groups 6-12 years and ≥18 years
Primary Endpoint Contrast sensitivity (Pelli Robson 3 m) at 6 months post-treatment
Key Secondary Endpoints Visual acuity, patient-reported outcomes, electroretinography
Study Design Randomized, wait list controlled, observer-masked trial
Key Inclusion Criteria Clinical diagnosis of achromatopsia, bi-allelic CNGA3 mutation, minimal outer nuclear layer thickness
Key Exclusion Criteria Other retinopathies, ocular malignancies, recent ocular surgery, systemic illnesses

FAQ

  • What is CNGA3-linked achromatopsia? CNGA3-linked achromatopsia is a rare genetic eye disorder characterized by the inability to perceive colors, poor visual acuity, and sensitivity to light. It is caused by mutations in the CNGA3 gene, which affects the function of cone cells in the retina responsible for color vision and visual acuity in bright light.
  • How is the gene therapy administered in this trial? The gene therapy, called rAAV.hCNGA3, is administered through a single subretinal injection in both eyes. This means the treatment is delivered directly beneath the retina, where it can target the affected cells responsible for color vision.
  • Who is eligible to participate in this clinical trial? The trial includes two age groups: children aged 6-12 years and adults 18 years and older. Participants must have a clinical diagnosis of achromatopsia, confirmed bi-allelic mutations in the CNGA3 gene, and meet other specific criteria related to eye health and overall medical condition.
  • What are the main goals of the Colour Bridge trial? The primary objective of the trial is to prove the safety and efficacy of rAAV.hCNGA3 when applied bilaterally (in both eyes) in adults and minors with CNGA3-linked achromatopsia. The study will assess various aspects of vision improvement, including contrast sensitivity, visual acuity, and patient-reported outcomes.
  • How long will participants be monitored after receiving the treatment? While the exact duration of follow-up is not specified in the provided information, the trial includes assessments at various time points, including a primary endpoint measurement at 6 months after treatment. Participants will likely be monitored for an extended period to evaluate long-term safety and efficacy.

Ongoing Clinical Trials on Adeno-Associated Viral Vector Serotype 8 Containing The Human Cnga3 Gene Under The Control Of A Cone Arrestin Promoter

  • Study on the Safety and Effectiveness of rAAV.hCNGA3 for Adults and Minors with CNGA3-Linked Achromatopsia

    Not recruiting

    1 1 1
    Investigated diseases:
    Investigated drugs:
    Germany

Glossary

  • Achromatopsia: A rare inherited eye disorder characterized by the absence or reduction of cone cell function in the retina, resulting in the inability to perceive colors, poor visual acuity, and light sensitivity.
  • CNGA3 gene: A gene that provides instructions for making a protein important for normal vision. Mutations in this gene can lead to CNGA3-linked achromatopsia.
  • rAAV.hCNGA3: The gene therapy product used in this trial, consisting of an adeno-associated viral vector carrying the human CNGA3 gene.
  • Subretinal injection: A method of delivering medication or gene therapy directly beneath the retina, the light-sensitive tissue at the back of the eye.
  • Contrast sensitivity: The ability to distinguish between finer and finer increments of light versus dark, measured in this study using the Pelli Robson test.
  • Visual acuity: The clarity or sharpness of vision, often measured using standardized eye charts like the ETDRS (Early Treatment Diabetic Retinopathy Study) chart.
  • Electroretinography: A diagnostic test that measures the electrical responses of various cell types in the retina, including rods and cones.
  • Chromatic pupil campimetry: A technique used to assess visual field function and color perception by measuring pupillary responses to colored light stimuli.
  • Bi-allelic mutation: A genetic condition where mutations are present on both copies of a particular gene, one inherited from each parent.
  • Outer nuclear layer: A layer of the retina containing the cell bodies of photoreceptor cells (rods and cones).

References

  1. http://clinicaltrials.eu/trial/study-on-the-safety-and-effectiveness-of-raav-hcnga3-for-adults-and-minors-with-cnga3-linked-achromatopsia/