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Long-term Safety and Efficacy Study of Gene Therapy for Choroideremia and X-Linked Retinitis Pigmentosa Using AAV2-REP1 and AAV8-RPGR in Previously Treated Patients

Verified siteInvestigationalNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on evaluating the long-term safety and effectiveness of a gene therapy for two eye conditions: Choroideremia and X-Linked Retinitis Pigmentosa. Choroideremia is a genetic disorder that leads to progressive vision loss, while X-Linked Retinitis Pigmentosa is a condition that affects the retina, causing gradual vision impairment. The study involves participants who have previously received specific gene therapies in earlier studies.

For Choroideremia, the treatment used is called AAV2-REP1, which is a type of gene therapy designed to deliver a healthy copy of a gene called REP1 to the eye. This therapy aims to prevent further vision loss or restore some lost vision function. For X-Linked Retinitis Pigmentosa, the treatment is AAV8-RPGR, which targets a different gene known as RPGR to help maintain or improve vision. Both treatments are administered through an injection directly into the eye.

The purpose of this study is to monitor the long-term effects of these treatments on participants who have already received them. Participants will undergo regular check-ups to assess their vision and overall eye health. The study will compare the outcomes of those who received the gene therapy with those who did not, to better understand the benefits and any potential risks associated with these treatments.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Participation begins after exiting a previous study involving retinal gene therapy.

    Eligibility requires prior treatment with specific gene therapies for choroideremia or X-linked retinitis pigmentosa.

  2. Step 2

    Initial assessment

    Initial assessments include a review of medical history and baseline measurements of visual acuity using the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart.

    Additional tests may include fundus photography, spectral-domain optical coherence tomography (SD-OCT), and microperimetry.

  3. Step 3

    Treatment administration

    The study involves monitoring the effects of previous treatments with adeno-associated viral vectors.

    No new medication is administered during this follow-up study.

  4. Step 4

    Ongoing assessments

    Regular follow-up visits are scheduled to monitor safety and efficacy.

    Assessments include visual acuity tests, fundus autofluorescence, and visual field evaluations.

  5. Step 5

    Final evaluation

    The study is expected to conclude by December 2026.

    Final assessments will compare changes from baseline in visual function and safety outcomes.

Who can join the trial?

4 criteria

  • Participants must be male.
  • Participants must be willing and able to give informed consent. This means they understand the study and agree to take part.
  • For those with Choroideremia (CHM), participants must have been part of a previous study that looked at the safety and effectiveness of a treatment called AAV2-REP1.
  • For those with X-Linked Retinitis Pigmentosa (XLRP), participants must have received a treatment called AAV8-RPGR and have been part of a previous study.

Who cannot join the trial?

4 criteria

  • Participants who have not been previously treated with the specific study treatments.
  • Participants who have not exited an earlier related study.
  • Females are not eligible to participate in this study.
  • Participants who are part of a vulnerable population, meaning those who might need special protection or care, are not eligible.
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Investigated drugs

  • AAV2-REP1

    is a gene therapy used for treating individuals with Choroideremia (CHM). This therapy involves a subretinal injection of a viral vector that carries the gene for Rab Escort Protein-1. The goal is to deliver the correct gene to the retina to help improve or stabilize vision in patients who have previously received this treatment in an earlier study.

  • AAV8-RPGR

    is another gene therapy designed for patients with X-Linked Retinitis Pigmentosa (XLRP). This treatment also involves a subretinal injection, but it uses a different viral vector to deliver the RPGR gene. The therapy aims to address the genetic cause of the disease and potentially improve or maintain vision in patients who have been treated with this therapy in a prior study.

What is already known about the treatment

  • AAV2-REP1

    This medication is administered through a subretinal injection, specifically targeting individuals with Choroideremia (CHM). It is currently being evaluated in clinical trials to assess its long-term safety and effectiveness. The main therapeutic indication is for treating CHM, a genetic condition that leads to progressive vision loss. At the molecular level, AAV2-REP1 works by delivering a gene that encodes Rab Escort Protein-1, which is essential for normal retinal function. It is classified as a gene therapy product.

  • AAV8-RPGR

    This medication is also delivered via subretinal injection and is intended for patients with X-Linked Retinitis Pigmentosa (XLRP). It is under investigation in clinical trials to determine its long-term safety and efficacy. The primary therapeutic indication is for XLRP, a genetic disorder that causes progressive vision impairment. AAV8-RPGR functions by introducing a gene that encodes the RPGR protein, crucial for maintaining healthy retinal cells. It falls under the category of gene therapy treatments.

Investigated diseases

  • Choroideremia

    Choroideremia is a rare genetic disorder that primarily affects males and leads to progressive vision loss. It is caused by mutations in the CHM gene, which results in the degeneration of the choroid, retina, and retinal pigment epithelium. The disease typically begins with night blindness in childhood, followed by a gradual loss of peripheral vision. Over time, central vision may also be affected, leading to significant visual impairment. The progression of vision loss varies among individuals, but it generally worsens with age.

  • X-Linked Retinitis Pigmentosa

    X-Linked Retinitis Pigmentosa (XLRP) is a genetic disorder that causes progressive degeneration of the retina, leading to vision loss. It is inherited in an X-linked manner, primarily affecting males, and is associated with mutations in several genes, including RPGR. The condition often begins with night blindness and a gradual loss of peripheral vision during adolescence or early adulthood. As the disease progresses, individuals may experience a narrowing of the visual field and eventual loss of central vision. The rate of progression can vary, but it typically leads to significant visual impairment over time.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-507994-16-00Protocol codeNSR-CHM-OS2 273CH201Estimated enrolment330 patientsSponsorBiogen Idec Research Limited

sourced from the EU Clinical Trials Register and site verification

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