Antioxidant pill shows promise in slowing blindness

NCT ID NCT05537220

Disease control Sponsor: Johns Hopkins University Source: ClinicalTrials.gov ↗

First seen Jun 27, 2026 · Last updated Jun 27, 2026

Summary

This phase 3 trial tests whether an oral antioxidant called N-acetylcysteine (NAC) can slow the loss of vision in people with retinitis pigmentosa, an inherited eye disease that causes gradual blindness. About 485 adults aged 18 to 65 are taking NAC or a placebo for several years. The goal is to see if NAC protects the light-sensing cells in the retina and preserves side and night vision.

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Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 3

Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.

Participants

485 people

The number who actually took part.

Started

Oct 2023

Expected to finish

May 2030

An estimate. End dates often move.

Lead sponsor

Other sponsor

The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 to 65 years

Sex

Anyone

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: General * Ability and willingness to provide informed consent * Age ≥ 18 and ≤65 years at time of signing Informed Consent Form * Ability and willingness to comply with the study protocol and to participate in all study visits and assessments in the investigator's judgement * For candidates of childbearing potential: willingness to use a method of contraception * Agreement not to take supplements other than vitamin A Ocular Inclusion Criteria * Both eyes must exhibit the RP phenotype with evidence of loss of night vision, gradual constriction of visual fields, and maintenance of visual acuity; * In addition, an eye must meet the following criteria to be included in the study: * Gradable EZ on a horizontal SD-OCT scan through the fovea center with width ≤ 8000 µm and ≥1500 µm and with well-defined truncation at both the nasal and temporal sides; * BCVA ≥ ETDRS letter score of 61 (20/60 Snellen equivalent); * Sufficiently clear ocular media and adequate pupillary dilation to allow good quality images sufficient for analysis and grading by central reading center. Exclusion Criteria: General Exclusion Criteria * Active cancer within the past 12 months, except for appropriately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, or prostate cancer with Gleason score ≤ 6 and stable prostate specific antigen for \> 12 months * Renal failure requiring renal transplant, hemodialysis, peritoneal dialysis, or anticipated to require hemodialysis or peritoneal dialysis during the study * Liver disease, cystic fibrosis, asthma, or chronic obstructive pulmonary disease (COPD), history of thrombocytopenia not due to a reversible cause or other blood dyscrasia * Uncontrolled blood pressure (defined as systolic \> 180 and/or diastolic \> 100 mmHg while at rest) at screening. If a patient's initial measurement exceeds these values, a second reading may be taken 30 or more minutes later. If the patient's blood pressure must be controlled by antihypertensive medication, the patient may become eligible if medication is taken continuously for at least 30 days. * History of other disease, physical examination finding, or clinical laboratory finding giving reasonable suspicion that oral NAC may be contraindicated or that follow up may be jeopardized * Cerebrovascular accident or myocardial infarction within 6 months of screening * Participation in an investigational study that involves treatment with any drug or device within 6 months of screening * Three relatives already enrolled in study * Pregnant, breast feeding, or intending to become pregnant during the study treatment period. Women of childbearing potential who have not had tubal ligation must have a urine pregnancy test at screening. * Known history of allergy to NAC * Having taken NAC in any form in the past 4 months * Phenylketonuria * Fructose intolerance * Glucose-galactose malabsorption * Sucrase-isomaltase insufficiency * Abnormal laboratory value including the value of alanine aminotransferase (ALT), aspartate aminotransferase (AST), or bilirubin being greater than 1.5 x the upper limit of normal * Any major abnormal findings on blood chemistry, hematology, and renal function lab tests that in the opinion of the Site Investigator and/or the Study Chair makes the candidate not suitable to participate in the trial * HIV or hepatitis B infection Ocular Exclusion Criteria * Evidence of cone-rod dystrophy or pattern dystrophy including focal areas of atrophy or pigmentary changes in the central macula * Cystoid spaces involving the fovea substantially reducing vision * Glaucoma or other optic nerve disease causing visual field loss or reduced visual acuity * Intra ocular pressure \>27 mm Hg from two measurements. If a patient's initial measurement exceeds 27 mm Hg, a second reading must be taken. * Any retinal disease other than RP causing reduction in visual field or visual acuity * Any prior macular laser photocoagulation * Intraocular surgery within 3 months prior to screening * High myopia with spherical equivalent refractive error \> 8 diopters. If an eye has had cataract surgery or refractive surgery, a pre-operative refractive error spherical equivalent \> 8 diopters is an exclusion * Any concurrent ocular condition that might affect interpretation of results * History of uveitis in either eye

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Conditions

The condition(s) this trial relates to.

retinitis pigmentosa Usher syndrome

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Retinitis pigmentosa

Contacts and locations

Locations

Emory University, Emory Eye Center

Atlanta, Georgia, 30322, United States
Harvard University, Mass. Eye and Ear

Boston, Massachusetts, 02114, United States
Mayo Clinic, Department of Ophthalmology

Rochester, Minnesota, 55905, United States
McGill University, The Research Institute of the McGill University Health Center

Montreal, Quebec, H4A 3J1, Canada
Medical College of Wisconsin, The Eye Institute

Milwaukee, Wisconsin, 53226, United States
Medical University of Graz, Department of Ophthalmology

Graz, Styria, 8036, Austria
Northwestern University

Evanston, Illinois, 60208, United States
Radboud University, Radboud University Medical Centre

Nijmegen, Gelderland, 6500 HB, Netherlands
Retina Foundation of the Southwest

Dallas, Texas, 75231, United States
Scheie Eye Institute

Philadelphia, Pennsylvania, 19104, United States
Stanford University, Byers Eye Institute

Stanford, California, 94303, United States
University College London, Moorfields Eye Hospital

London, England, United Kingdom
University Of Illinois At Chicago

Chicago, Illinois, 60612, United States
University of Amsterdam, Amsterdam Medical Center

Amsterdam, Northern Holland, 1105 AZ, Netherlands
University of California - Davis, Department of Ophthalmology & Vision Science

Davis, California, 95817, United States
University of California - San Francisco, Department of Ophthalmology

San Francisco, California, 94158, United States
University of Florida - Jacksonville, UF Health Jacksonville

Jacksonville, Florida, 32209, United States
University of Iowa, Carver College of Medicine

Iowa City, Iowa, 52242, United States
University of Miami, Bascom Palmer Eye Institute

Miami, Florida, 33136, United States
University of Michigan, Kellogg Eye Center

Ann Arbor, Michigan, 48105, United States
University of Minnesota, Department of Ophthalmology and Visual Neurosciences

Minneapolis, Minnesota, 55455, United States
University of Oklahoma, Dean McGee Eye Institute

Oklahoma City, Oklahoma, 73104, United States
University of Southern California, Keck School of Medicine

Los Angeles, California, 90089, United States
University of Tübingen, Department für Augenheilkunde

Tübingen, Baden-Wurttemberg, 72076, Germany
University of Utah, Moran Eye Center

Salt Lake City, Utah, 84132, United States
University of Washington, Department of Ophthalmology

Seattle, Washington, 98109, United States
University of Wisconsin - Madison, McPherson Eye Research Institute

Madison, Wisconsin, 53705, United States
Universitätsspital Basel, Eye Clinic

Basel, CH-4031, Switzerland
Vanderbilt University, Vanderbilt Eye Institute

Nashville, Tennessee, 37211, United States
Vitreo Retinal Associates

Gainesville, Florida, 32607, United States
Wilmer Eye Institute- Johns Hopkins University

Baltimore, Maryland, 21287, United States

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