FIGHT-RP 1 Extension Study

October 7, 2025 updated by: Johns Hopkins University

A Phase 1 Open-Label Extension Study to Assess the Long-Term Safety and Tolerability of N-Acetylcysteine (NAC) in Patients With Retinitis Pigmentosa

Retinitis Pigmentosa (RP) is a devastating eye disease and at present there are no known treatment options that can alter the rate of vision loss and eventual blindness. In a series of studies in animal models, the effects of exposing cones in the periphery of the retina to a large excess of oxygen results in progressive oxidative damage to cone photoreceptors and cone cell death. Cone cell death gradually spreads from the periphery of the retina toward its center, narrowing the visual field and eventually resulting in tunnel vision. Compared to control patients, those with RP showed significant reduction in the reduced to oxidized glutathione ratio (GSH/GSSG) in aqueous humor and a significant increase in protein carbonyl content. This demonstration of oxidative stress and oxidative damage in the eyes of patients with RP, suggests that oxidative damage-induced cone cell death in animal models of RP may translate to humans with RP and support the hypotheses that (1) potent antioxidants will promote cone survival and function in patients with RP and (2) aqueous GSH/GSSG ratio and carbonyl content on proteins provide useful biomarkers of disease activity in this patient population. Orally administered N-acetylcysteine (NAC) has been found to be a particularly effective antioxidant that promotes prolonged cone survival and maintenance of cone function in a mouse model of RP. Since oral and/or topical administration of NAC is feasible for long-term treatment in humans, and NAC has a good safety profile, there is good rationale to test the effect of NAC in patients with RP.

Oxidative damage has been implicated in several diseases including cystic fibrosis, chronic obstructive pulmonary disease (COPD), and Idiopathic Pulmonary Fibrosis. The effect of oral NAC has been tested in these indications in several clinical trials providing extensive safety data. In COPD, NAC 600mg bid improves airway function and reduces the frequency of acute exacerbations. Doses of up to 1800mg/day have been well-tolerated in the treatment of Idiopathic Pulmonary Fibrosis. Paracetamol (acetaminophen) toxicity is treated with a loading dose of 140 mg/kg NAC followed by 70 mg/kg every 4 hours for 17 doses. Normal volunteers tolerated a dose of 11.2 grams NAC/day for three months without any serious undesirable effects and in another study a dose of 500mg/kg/day was tolerated. The most frequent adverse events associated with the oral administration of NAC are gastrointestinal in nature and include vomiting, diarrhea, stomatitis, abdominal pain and nausea (incidence rate >1/1000 to <1/100). Hypersensitivity reactions including anaphylactic shock and anaphylactic/anaphylactoid reaction (incidence rate <1/10,000), dyspnea, bronchospasm (incidence rate >1/10,000 to <1/1000), angioedema, tachycardia, urticaria, rash and pruritus (incidence rate >1/1000 to <1/100) have been reported less frequently. Finally, reports of headache, tinnitus, pyrexia, blood pressure decreased (incidence rate >1/1000 to <1/100), face edema and hemorrhage have also been collected with oral NAC.

In the FIGHT-RP 1 Study, the investigators used escalating doses of NAC effervescent tablets (from 600 mg in Cohort 1 to 1800 mg in Cohort 3). The maximum tolerated dose was 1800 mg twice a day which will be continued in this study.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
30

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Maryland
      • Baltimore, Maryland, United States, 21287
        • Wilmer Eye Institute at Johns Hopkins University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age 18 years
  • Patients diagnosed with RP
  • Informed consent
  • Authorization of use and disclosure of protected health information

Exclusion Criteria:

  • Patients with a concomitant ocular pathology that limits central macular function, including but not limited to: age-related macular degeneration, diabetic retinopathy, and retinal vein occlusion
  • Patients with an active ocular infection
  • Patients with uncontrolled hypertension (defined as diastolic blood pressure > 95 mm Hg or systolic blood pressure > 160 mm Hg despite medical therapy)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Experimental Arm
All participants to receive study intervention.
Drug: NAC effervescent tablets
After completing the pretreatment visits, all patients will enter into the treatment phase where patients will receive 1800 mg of NAC effervescent tablets twice a day. The patients will be followed up every 3 months for 2 years. Therefore, there will be a total of 9 treatment visits (baseline, months 3, 6, 9, 12, 15, 18, 21 and 24).

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Blood Pressure (mmHg)
Time Frame: Up to 2 years
Blood pressure in mmHg will be used in assessing tolerability of N-Acetylcysteine.
Up to 2 years
Tolerability of N-Acetylcysteine as assessed by drug-related symptoms
Time Frame: Up to 2 years
Participants will be assessed for the occurrence of any drug-related symptoms which includes nausea, stomach upset, diarrhea, heartburn, constipation, and vomiting. Based on the number and severity of the symptoms, the physician would conclude whether the patient is tolerating the medication or not.
Up to 2 years
Tolerability of N-Acetylcysteine as assessed by time at which medication is taken
Time Frame: Up to 2 years
Medication diary provided to participants will be reviewed to see if participants are taking the medication within the designated time frame.
Up to 2 years
Tolerability of N-Acetylcysteine as assessed by number of times medication is taken per day
Time Frame: Up to 2 years
Medication diary provided to participants will be reviewed to see if participants are taking the medication twice a day
Up to 2 years

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Change in best corrected visual acuity (BCVA)
Time Frame: Baseline, every three months up to 2 years
Scoring is determined by the number of letters gained or lost per month using Early Treatment Diabetic Retinopathy Study (ETDRS) Letter Score and visual acuity score together with an overall score range of 0 to 20/20 where 0 is the worst vision and 20/20 is the best.
Baseline, every three months up to 2 years
Change in central retinal sensitivity as assessed by microperimetry
Time Frame: Baseline, every three months up to 2 years
Microperimetry (MAIA) is used to test whether there is an increase or decrease in sensitivity (dB) in the retina after initiation of N-Acetylcysteine
Baseline, every three months up to 2 years
Change in ellipsoid zone (EZ) width (µm)
Time Frame: Baseline, every three months up to 2 years
This will be assessed by spectral domain optical coherence tomography (SD-OCT) after initiation of N-Acetylcysteine.
Baseline, every three months up to 2 years
Change in aqueous reduced to oxidized glutathione ratio (GSH/GSSG)
Time Frame: Baseline, every three months up to 2 years
This will be calculated from the proportions of reduced glutathione and oxidized glutathione in the aqueous.
Baseline, every three months up to 2 years
Change in serum carbonyl content (nmol/mg)
Time Frame: Baseline, every three months up to 2 years
Baseline, every three months up to 2 years
Change in aqueous levels of N-Acetylcysteine (mg)
Time Frame: Baseline, every 6 months up to 2 years
Baseline, every 6 months up to 2 years
Change in plasma levels of N-Acetylcysteine (µg/ml)
Time Frame: Baseline, every 3 months up to 2 years
Baseline, every 3 months up to 2 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Johns Hopkins University

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Zambon SpA

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Peter Campochiaro, Johns Hopkins University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
June 24, 2019

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
August 1, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
June 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
June 24, 2019

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 24, 2019

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
June 26, 2019

Study Record Updates

Last Update Posted (Estimated)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
October 9, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 7, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • IRB00204017

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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