DHA and X-Linked Retinitis Pigmentosa
Condition: Retinitis Pigmentosa; X-linked Genetic Diseases
MeSH terms: Retinitis; Retinitis Pigmentosa; Genetic Diseases, Inborn; Genetic Diseases, X-Linked
Intervention: docosahexaenoic acid OR corn/soy oil placebo
Intervention description: daily intake of DHA based on body weight or corn/soy oil placebo(oil not containing DHA; 4 year trial
Phase: Phase 2
Study type: Interventional
Primary purpose: Prevention
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Enrollment: 78.0
Sex: Male
Minimum age: 7 Years
Maximum age: 32 Years
Healthy volunteers: No
Keywords: retina; electroretinography; clinical trial; docosahexaenoic acid; omega-3 fatty acid; x-linked inheritance

Summary:

      Purpose:

      Retinitis pigmentosa (RP) is characterized by progressive loss of visual function due to
      specific genetic mutations. This trial is focused on patients with one of the most severe
      forms of the disease, X-linked inherited RP (XLRP). This disease is characterized by early
      onset (typically loss of night vision as a child) followed by loss of peripheral vision as a
      teenager and young adult. There is no male-to-male transmission of the disease in the family.

      There is no cure for RP and treatment options are limited. Two clinical trials have not found
      a benefit from nutritional supplementation with the long-chain polyunsaturated fatty acid,
      docosahexaenoic acid (DHA), at low daily doses although there is evidence that it slows
      disease progression in certain instances. In this clinical trial, we propose that a high dose
      nutritional DHA supplement will slow the loss of visual function and preserve usable vision
      in patients with XLRP.

      This study is a 4-year placebo-controlled randomized clinical trial meaning that patients
      have a 50-50 chance of receiving placebo or experimental treatment. A total of 66 patients
      will be enrolled; 33 will receive placebo and 33 will receive the treatment. Entry criteria
      include diagnosis of XLRP by an ophthalmologist, age 7 to 32 years, male, sufficient visual
      function such that disease progression can be followed for the entire duration of the trial,
      and a willingness to visit the testing site (Dallas, TX) once a year.

      Annual visual function testing includes ETDRS visual acuity, full-field and multifocal
      electroretinography (ERG), static peripheral visual fields, and fundus photography. Cone ERG
      function is the primary outcome measure.

      Funding Source - FDA, Foundation Fighting Blindness, DSM Nutritionals
    

Eligibility criteria:

        Inclusion Criteria:

          -  Diagnosis of RP by a retinal specialist

          -  Clinical diagnosis consistent with X-linked inheritance

          -  Enrolling minors and young adults (early onset of X-linked disease; ages 7 to 32)

          -  Measurable cone ERG responses --patients with less than 0.64 microvolt response to
             31-Hz flicker will be excluded as they are more likely to become undetectable during
             the study

          -  Both eyes must meet entry criteria as both will be tested (i.e., no cataracts
             requiring surgery or retinal detachments).

          -  Media clarity sufficient for fundus photography

          -  Able to return to study site at yearly intervals

          -  Willing to supply blood samples at 6-month intervals

          -  Judiciously take the placebo or DHA supplement for the 4-year study duration

          -  Patient/parent/guardian understands and signs consent form.

        Exclusion Criteria:

          -  Excessive fish consumption (e.g., cold water fish such as salmon, tuna, sardines)
             and/or fish oil supplementation (or other oil containing DHA)

          -  Baseline RBC-DHA levels showing evidence of supplementation (a typical level of
             RBC-DHA in normals is about 3.8%)

          -  Chronic metabolic disease that may interfere with fatty acid metabolism or require
             anti-coagulant medication

        No ethnic or racial groups will be excluded.