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Effects of Treatment With N- Acetylcysteine on Visual Outcomes in Patients With Retinitis Pigmentosa

  • identifier


  • Recruitment Status

    Active, not recruiting

  • First Posted

    April 29, 2021

  • Last update posted

    April 29, 2021

Study Description

Brief summary:

Retinitis pigmentosa (RP) is an inherited retinal disease with great heterogeneity. RP comprises a large group of genetic disorders causing progressive loss of vision. Despite many suggested treatments, there is actually no effective therapy for most types of RP at present. Mutations that cause RP initially lead to rod cell death. After rod photoreceptors' death, cone photoreceptors also gradually die. There are several hypotheses as to why mutation-induced rod photoreceptor cell death invariably leads to gradual dysfunction and death of cone photoreceptors resulting in severe visual acuity loss and blindness. Rods constitute 95 percent of cells in the outer retina. As they degenerate, oxygen consumption is reduced and the level of tissue oxygen markedly increases. After rods degeneration, several markers of oxidative damage appear in cones. This oxidative stress over time may lead to cone dysfunction and death. Antioxidants reduce markers of oxidative damage and promote cone function and survival. In RP, cone death occurs as a result of the death of rods, rather than as the result of the pathogenic mutations and therefore treatment with antioxidants may have the potential to be applied to all patients with RP irrespective of the disease-causing mutation. N-acetylcysteine is a derivative of L cysteine that plays a role in the biosynthesis of glutathione and neutralizes reactive oxygen species. It also has a direct antioxidant activity via its reactive sulfhydryl agent. Its systemic use shows an acceptable safety profile. It has been shown that the use of systemic N-acetylcysteine provides significant intraocular concentration and antioxidant activity that may lead to the promotion of cone function and survival. In a recent phase 1 randomized clinical trial (RCT), it was revealed that oral N-acetylcysteine (NAC) was safe and well-tolerated in patients with moderately advanced RP and might improve sub-optimally functioning macular cones. The authors concluded that a randomized, placebo-controlled trial is needed to determine if oral NAC can provide long-term stabilization and/or improvement in visual function in patients with RP. In this phase 2 RCT, eligible patients with the diagnosis of moderately advanced RP are randomly divided into two groups; treatment group (N-acetylcysteine tablets) and controls (placebo). Each group will be treated for 6 months. In this study, we will investigate if the use of oral N- acetylcysteine as a potent antioxidant agent can slow down or reverse the disease process in RP patients with prior moderate loss of vision. It may potentially demonstrate a treatment modality regardless of the genetic type of RP. The primary outcome measure will be the stability or improvement of the best-corrected visual acuity (BCVA). The secondary outcome measures will be changes in color vision, electroretinogram, visual field, structural OCT indices after 6 months. The same parameters will be re-evaluated 3 months after discontinuation of treatment at month 9.

  • Condition or Disease:Retinitis Pigmentosa
  • Intervention/Treatment: Drug: Prescribe N-acetylcysteine tablets
    Drug: Prescribe placebo tablets
  • Phase: Phase 2

Detailed Description


Study Design

  • Study Type: Interventional
  • Estimated Enrollment: 30 participants
  • Allocation: Randomized
  • Intervention Model: Parallel Assignment
  • Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
  • Primary Purpose: Treatment
  • Official Title: Effects of Oral N- Acetylcysteine on Macular Function in Retinitis Pigmentosa; a Phase 2 Randomized Controlled Trial
  • Actual Study Start Date: April 2021
  • Estimated Primary Completion Date: March 2022
  • Estimated Study Completion Date: December 2022

Arms and interventions

Arm Intervention/treatment
Active Comparator: Prescribe N-acetylcysteine tablets
Drug: Prescribe N-acetylcysteine tablets
N-acetylcysteine tablets ,1200 mg two times daily
Placebo Comparator: Prescribe placebo tablets
Drug: Prescribe placebo tablets
manufactured by Daroo Salamat Pharmed, two times daily

Outcome Measures

  • Primary Outcome Measures: 1. Change of the best corrected visual acuity (BCVA) from baseline to month 6 [ Time Frame: 6 months ]
    ETDRS chart
  • Secondary Outcome Measures: 1. Change of the ellipsoid zone (EZ) width from baseline to month 6 [ Time Frame: 6 months ]
    spectral domain optical coherence tomography (SD-OCT)
  • 2. Changes of the wave amplitude of the flicker response from baseline to month 6 [ Time Frame: 6 months ]
    Full field electroretinograph (ffERG) testing
  • 3. Change of the foveal and macular sensitivity from baseline to month 6 [ Time Frame: 6 months ]
    visual field testing
  • 4. Change of the color discrimination parameters from baseline to month 6 [ Time Frame: 6 months ]
    D15 Fransworth 100 Hue Test

Eligibility Criteria

  • Ages Eligible for Study: 18 to 40 Years (Adult)
  • Sexes Eligible for Study: All
  • Accepts Healthy Volunteers: No


Inclusion Criteria: RP patients with the best-corrected visual acuity (BCVA) between 20/30 and 20/120. Exclusion Criteria: Patients with other types of retinal dystrophy Systemic or syndromic RP RP patients with cystoid macular edema (CME) and the presence of cystoid changes in the foveal area RP patients with other concomitant ocular diseases RP patients with a history of any ocular surgery or intravitreal injection within 6 months before the study enrollment RP patients who have received any supplemental drugs during the past three months before the study enrollment

Contacts and Locations



Iran, Islamic Republic of
Ophthalmic Research Center

Sponsors and Collaborators

Shahid Beheshti University of Medical Sciences

More Information

  • Responsible Party: Shahid Beheshti University of Medical Sciences
  • Identifier: NCT04864496 History of Changes
  • Other Study ID Numbers: 1400
  • First Posted: April 29, 2021 Key Record Dates
  • Last Update Posted: April 29, 2021
  • Last Verified: April 2021
  • Studies a U.S. FDA-regulated Drug Product: No
  • Studies a U.S. FDA-regulated Device Product: No
  • Additional relevant MeSH terms: Retinitis
    Retinitis Pigmentosa
    Retinal Diseases
    Eye Diseases
    Eye Diseases, Hereditary
    Retinal Dystrophies
    Retinal Degeneration
    Genetic Diseases, Inborn