REP1 Gene Replacement Therapy for Choroideremia


The assessment of the efficacy (with respect to preservation of visual function and retinal structure) and safety of a single subretinal injection of AAV2.REP1 in participants with a confirmed diagnosis of choroideremia, as evaluated by various functional and anatomical outcomes measured over a number of time points up to 24 months post-treatment.

Full Title of Study: “An Open Label Phase 2 Clinical Trial of Retinal Gene Therapy for Choroideremia Using an Adeno-associated Viral Vector (AAV2) Encoding Rab-escort Protein 1 (REP1)”

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Treatment
    • Masking: None (Open Label)
  • Study Primary Completion Date: August 2021


  • Genetic: AAV-mediated REP1 gene replacement
    • AAV vector carrying human REP1 gene is delivered into the treated eye by subretinal injection

Arms, Groups and Cohorts

  • Experimental: Treatment
    • Treated eye undergoes AAV-mediated REP1 gene replacement. AAV vector is delivered by subretinal injection.
  • No Intervention: Control
    • Untreated eye

Clinical Trial Outcome Measures

Primary Measures

  • Change from baseline in best corrected visual acuity in the treated eye
    • Time Frame: 2 years

Secondary Measures

  • Change from baseline in the central visual field in the treated eye as determined by microperimetry
    • Time Frame: 2 years
  • Change from baseline in the area of surviving retinal pigment epithelium in the treated eye as measured by fundus autofluorescence, compared to the untreated fellow eye (control eye) after randomisation of treatment to one eye or the other
    • Time Frame: 2 years

Participating in This Clinical Trial

Inclusion Criteria

1. Candidate is willing and able to give informed consent for participation in the study. 2. Male aged 18 years or above. 3. Genetic or molecular confirmed diagnosis of choroideremia (REP1 protein deficiency). 4. Active disease visible clinically within the macula region. 5. Best corrected visual acuity better than or equal to 6/60 (20/200; Decimal 0.1; LogMAR 1.0) in the study eye. Exclusion Criteria:

1. Any female, or a male aged below 18 years. 2. An additional cause for sight loss (e.g. amblyopia) in the eye to be treated. 3. Any other significant ocular and non-ocular disease or disorder which, in the opinion of the investigator, may put the participants at risk because of participation in the study. 4. Inability to take systemic prednisolone for a period of 45 days. 5. Unwillingness to use barrier contraception methods for a period of three months following gene therapy surgery. 6. Participation in another research study involving an investigational product in the preceding 12 weeks.

Gender Eligibility: Male

Minimum Age: 18 Years

Maximum Age: 90 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • University of Oxford
  • Collaborator
    • Moorfields Eye Hospital NHS Foundation Trust
  • Provider of Information About this Clinical Study
    • Sponsor
  • Overall Official(s)
    • Robert E MacLaren, MB ChB DPhil, Principal Investigator, University of Oxford

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