What is Retinitis Pigmentosa?

Retinitis pigmentosa (RP) is an inherited retinal disease resulting from one or multiple genetic mutations. The mutations cause death of photoreceptor cells, resulting in the first symptom of loss of night vision. Then gradually, patients start to notice constricted visual fields followed by loss of visual acuity over years or decades until legal blindness. RP is one of the most common causes of blindness and severe low-vision in people aged 20 to 60 years. The estimated population prevalence is 1 in 3500-4000 in the US and Europe. Currently, there is no therapeutic treatment for RP. Learn more about retinitis pigmentosa

N-acetylcysteine (NAC) is an antioxidant naturally present in onions. An intravenous formulation of NAC is an FDA approved medication used to treat acetaminophen (paracetamol) overdose and as a mucolytic for cystic fibrosis and other pulmonary diseases.

What is NAC Attack and why is it needed?

NAC Attack is a Phase III multicenter, randomized, placebo-controlled, double masked study to evaluate the efficacy and safety of oral NAC of 1800mg bid in patients with RP. Pre-clinical studies have proven that excessive oxidative stress plays a key role in photoreceptor cell death in RP. NAC is an antioxidant and its effect on reducing photoreceptor loss was shown in animal studies . In a phase-1 open label study conducted at the Wilmer Eye Institute, oral NAC treatment was given to 30 patients with RP for 6 months . This study observed 1800mg twice per day was tolerable. This supports the next step of a multicenter, randomized, placebo-controlled and masked clinical trial in a larger population and over a longer time in order to determine the long-term safety of NAC 1800 mg twice per day and determine whether oral NAC can slow photoreceptor loss and thus delay visual function loss in patients with RP.

Why is a randomized, placebo-controlled trial, and double masked trial needed?

A randomized, placebo-controlled trial means that study patients are randomly assigned to receive the experimental intervention treatment or the placebo that resembles the intervention treatment but does not contain the active intervention component. Because the assignment is random, patients receiving the intervention and patients receiving the placebo are expected to be very similar. Thus, any difference between the two patient groups with respect to disease-related outcomes is most likely due to the treatment the patient received (i.e. intervention or placebo control). Moreover, “double masked” means both the study patient participants and study doctors, nurses and coordinators do not know whether a participant is receiving active study medication or placebo. This is to minimize any potential subconscious bias so the study can objectively measure changes in visual function in the participants. Such a study design (“randomized, placebo-controlled, and double masked” clinical trial) is known to be the “gold standard” for determining whether the intervention indeed works for the disease.

I see NAC is available in the drug store. Should I just buy it and start taking it?

No, we do not yet know whether NAC is truly helpful and not harmful, especially long-term use of NAC at the study dose of 1800mg twice per day, so we do not recommend taking it outside of a closely monitored situation like a clinical trial. In addition, the NAC available in drug stores or online is supplement grade NAC, which is not regulated, meaning that the producers do not have to measure exactly what is in it. Some newly marketed combination supplements contain NAC, vitamins and other ingredients that are thought to be good for eyes. However, the safety of such combination supplements is particularly of question as we do not know if there are potential drug interactions with the simultaneous use of different antioxidants.

When will we know NAC Attack study results?

NAC Attack completed its recruitment in August 2025. Study participants are followed for 45 months after enrollment. The study will have an interim readout of progression data in early 2028, and by the end of 2029 when all participants completed their 45-month follow-up visit, we will be able to analyze the data and have the ultimate answer of whether NAC is safe and effective in slowing RP progression.

NAC Attack Clinical Trial

NAC Attack: A Multicenter, Placebo-Controlled Clinical Trial To Test Oral N-Acetylcysteine in Patients

NAC Attack is an international phase-III clinical trial designed to determine whether taking oral N-Acetylcysteine (NAC) 1800mg twice per day is safe and effective in slowing vision loss in patients with retinitis pigmentosa (RP). This largest study of RP is funded by the National Eye Institute of the United States. By the end of August 2025, the study reached its recruitment goal and successfully recruited 485 eligible RP patients from 31 clinical sites across the United States, Canada, Austria, Germany, the Netherlands, Switzerland, and the United Kingdom. The support from the RP community has been extraordinary: Over 630 patients participated in screening and many others who expressed interest. The study unfortunately could not enroll everyone, but once NAC Attack is finished, the knowledge gained from the study will help the RP and even the broader inherited retinal diseases community, for generations to come.

NAC Attack Investigative Group Meeting

NAC Attack participating institutions from around the world met in Atlanta, GA in February for the annual NAC Attack Investigative Group Meeting. See photos of the participating presenters below.

A Team Effort!

Conference attendees pose for a group photo.

Meeting Registration

NAC Attack Staff at the registration table for the conference.

Participants at the Friday Night Banquet Dinner!

Conference attendees at the Friday night banquet dinner.

NAC Attack researchers at the Friday night banquet dinner

NAC Attack Investigative Group Meeting February 1, 2025

Peter Campochiaro, study chair of the NAC Attack study, presenting to the assembled researchers.

Xiangrong Kong: NAC Attack Coordinating Center Director and Senior Biostatistician

Xiangrong Kong presents to the conference attendees.

Xiangrong Kong, coordinating director and senior biostatistician, presenting at the conference.

OCT Reading Center, Duke University

Glenn Jaffe and April Flora from the OCT Reading Center at Duke University present at the conference.

Glenn Jaffe and April Flora from the OCT Reading Center at Duke University presenting.

Muhammad Jehanzeb Khan, Study Chair's Office, Johns Hopkins University, Wilmer Eye Institute

Muhammad Jehanzeb Khan from the study chair's office at Johns Hopkins University, Wilmer Eye Institute.

Muhammad Jehanzeb Khan presenting at the conference.

Yuki Wiland, Harvard University

Yuki Wiland from Massachusetts Eye and Ear at Harvard University presents to the conference.

Yuki Wiland from Harvard presenting at the conference.

Raymond Lezzi, Mayo Clinic

Raymond Iezzi from the Mayo Clinic presents on the OPUS Bioinformatics system.

Raymond Iezzi from Mayo clinic presenting at the conference.

Hailey Ahrens, Vitreo Retinal Associates

Hailey Ahrens from Vitreo Retinal Associates presents to the conference.

Hailey Ahrens from Vitreo Retinal Associates presenting to the conference.

Mariana Edwards and Kimberly Rodriguez, University of Southern California

Mariana Edwards (left) and Kimberly Rodriguez (right) from the University of Southern California present to the conference.

Mariana Edwards and Kimberly Rodriguez presenting to the conference.

Zainab Rustam, Study Chair’s Office, Johns Hopkins University, Wilmer Eye Institute

Zainab Rustam from the Study Chair's office presents on "Repeatability of Best Corrected Visual Acuity (BCVA) and Ellipsoid Zone (EZ) Width In Eyes With Retinitis Pigmentosa (RP)."

Zainab Rustam presenting on the subject "Repeatability of Best Corrected Visual Acuity (BCVA) and Ellipsoid Zone (EZ) Width In Eyes With Retinitis Pigmentosa (RP)."

Alexandra Versleijen, Radboud University, the Netherlands

Alexandra Versleijen from Radboud University in the Netherlands presents to the conference.

Alexandra Verselijen from Radboud University in the Netherlands presenting to the conference.

Rupert Strauss, Medical University Graz, Austria

Rupert Strauss from Medical University Graz in Austria presents to the conference.

Rupert Strauss from Medical University Graz in Austria presenting at the conference.

Petra Rossouw, University of Basel, Switzerland

Petra Rossouw from the University of Basel, Switzerland presents to the conference.

Laura Kuehlewein, University of Tubingen, Germany

Laura Kuehlewein from University of Tubingen, Germany presenting on "Lens Abnormalities and Associated Risk Factors in Retinitis Pigmentosa."

Laura Kuehlewein from University of Tubingen, Germany presenting at the conference.

Ronald van Leersum, Amsterdam University, the Netherlands

Ronald van Leersum from Amsterdam University, in the Netherlands presents to the conference.

Ronald van Leersum, from Amsterdam University in the Netherlands, presenting at the conference.

Research presentation, Izzie Wang, NAC Attack Coordinating Center, Johns Hopkins University

Izzie Wang from the NAC Attack Coordinating Center presenting on the subject "Factors associated with microperimetry false positive responses in patients with retinitis pigmentosa."

Research presentation, Alyssa Bonnell and Jennifer Chao, University of Washington

Alyssa Bonnell and Jennifer Chao presented on the subject "Endogenous Levels of N-acetylcysteine in Human Plasma in the NAC Attack Study."

Milam Brantley, Vanderbilt University

Milam Brantley from Vanderbilt University presents to the conference.

Milam Brantley from Vanderbilt presenting.

Shivani Kochhar, University of Florida

Shivani Kochhar from the University of Florida presents to the conference.

Shivani Kochhar from University of Florida.

Mary McCormick, University of Iowa

Mary McCormick from the University of Iowa presents to the conference.

Adriana Padilla Drada, University of Miami

Adriana Padilla Drada from the University of Miami presents to the conference.

Grace Trigler, University of Oklahoma

Grace Trigler from the University of Oklahoma presenting to the conference.

Research Presentation, Hossein Ameri, University of Southern California

Hossein Ameri from the University of Southern California presenting on the topic "Vitreous Abnormalities and Associated Risk Factors in Retinitis Pigmentosa."

Meaghyn Kramer, University of Minnesota

Meaghyn Kramer from the University of Minnesota presenting to the conference.

Daphné Doucet, McGill University

Daphné Doucet from McGill University presenting to the conference.

Callie Gordon, University of Michigan

Callie Gordon from the University of Michigan presenting to the conference.

Lorraine Almeda, Stanford University

Lorraine Almeda from Stanford University presenting to the conference.

Denise Macias, University of California Davis

Denise Macias from the University of California Davis presenting to the conference.

Rob Hufnagel, Kaiser Permanente Hawaii

Rob Hufnagel from Kaiser Permanente Hawaii presenting on the Genetics Data Collection Plan.

Rodrigo Matsui Serrano, Instituto de Oftalmología Fundación Conde de Valenciana, Mexico

Rodrigo Matsui Serrano from the Instituto de Oftalmología Fundación Conde de Valenciana, Mexico presenting to the conference.

Fred Collison, Northwestern University

Fred Collison from Northwestern University presenting to the conference.

Susie Trotochaud, USHER 2020 Foundation

Susie Trotochaud from the USHER 2020 Foundation presenting to the conference.

Joseph Kreis, Medical College of Wisconsin, AOSLO Reading Center

Joseph Kreis from the Medical College of Wisconsin, AOSLO Reading Center, presenting to the conference.

David Birch, Retina Foundation of the Southwest

David Birch from the Retina Foundation of the Southwest presenting to the conference.

Nancy Aychoua, Moorfields Eye Hospital, University College London

Nancy Aychoua from Moorfields Eye Hospital, University College, London, presenting to the conference.

Alexandra Garafalo, University of Pennsylvania

Alexandra Garafalo from the University of Pennsylvania presenting to the conference.

Nicole Boone and Nickie Stangel, University of Wisconsin, Madison

Nicole Boone and Nickie Stangel from the University of Wisconsin, Madison presenting to the conference.

University of Wisconsin, Madison , Nicole Boone (left) and Nickie Stangel (right)

Katie McKenney, Medical College of Wisconsin

Katie McKenney from the Medical College of Wisconsin presenting to the conference.

Jenna Huey, University of Washington

Jenna Huey from the University of Washington presenting to the conference.

Jianrong Shen, University of Illinois, Chicago

Jianrong Shen from the University of Illinois, Chicago presenting to the group.

Paul Bernstein, University of Utah

Paul Bernstein from the University of Utah presenting to the conference.

Nieraj Jain, Emory University

Nieraj Jain from Emory University presenting to the conference.

Folahan Ibukun, NAC Attack Coordinating Center, Johns Hopkins University

Folahan Ibukun, from the NAC Attack Coordinating Center, Johns Hopkins University presenting to the conference.

NAC Attack Study News

NAC Attack held their inaugural in-person investigative group meeting during the ARVO (Association for Research in Vision and Ophthalmology) conference in Seattle, WA on May 6th, 2024

NAC Attack at ARVO

Xiangrong Kong, PhD. Director, NAC Attack Coordinating Center closing the meeting.

NAC Attack at ARVO

Peter Campochiaro, MD. NAC Attack Study Chairman presenting learnings from screening and adverse events.

NAC Attack at ARVO

Glen Jaffe, MD. Director of the Duke Reading Center presenting tips and tricks for NAC Attack study imaging.

NAC Attack at ARVO

Jacque Duncan, MD. AOSLO Reading Center Co-director presenting updates on the AOSLO sub-study.

NAC Attack at ARVO

Attendees listening to presenters at ARVO.

NAC Attack at ARVO

Dagmar Wehling, COA. Clinical Research Coordinator at Johns Hopkins University sharing site learnings from patient recruitment and study visit coordination.

NAC Attack at ARVO

Mariana Edwards, BSc. Clinical Research Coordinator at University of Southern California sharing her experience with study coordination.

NAC Attack at ARVO

Meaghyn Kramer, B.A. Clinical Research Coordinator at University of Minnesota presenting on NAC Attack participant recruitment and retention.

NAC Attack at ARVO

Attendees listening to presenters at ARVO.

NAC Attack at ARVO

Attendees listening to presenters at ARVO.

NAC Attack at ARVO

Alex Garafalo, MEng. Clinical Research Coordinator at University of Pennsylvania, US, and Ha Diep, Clinical Research Coordinator at Radboud University Medical Center, Netherlands sharing experiences on patient engagement via Zoom.

NAC Attack at ARVO

A group photo of NAC Attack attendees at ARVO!

Frequently Asked Questions

NAC Attack Video FAQ

Select the language you want from the list of available languages.

English | Closed captioning is available by clicking the "CC" icon in the bottom right corner.

Nederlands | Tik op Ondertiteling "CC." Selecteer de taal waarin je de ondertiteling wilt zien.

Français | Appuyez sur Sous-titres "CC ". Sélectionnez la langue dans laquelle vous souhaitez afficher les sous-titres.

Deutsch | Tippe auf das Untertitelsymbol "CC". Wähle die Sprache aus, in der die Untertitel angezeigt werden sollen.

Español | Toca Subtítulos "CC". Elige el idioma en el que quieras ver los subtítulos.

NAC Attack | Important Things To Remember

Watch on

NAC Attack | Caring for Your Medication

Watch on

NAC Attack | Using the Medication

Watch on

NAC Attack | What To Expect at Your Health-care Visits

Watch on

NAC Attack | What To Do if You Have a Question

Watch on

Clinical Sites

NAC Attack is actively following study participants at 31 clinical sites in the US, Canada and Europe. A list of the 31 participating NAC Attack Clinical sites and their geographic locations can be found below.

NAC Attack Clinical Site Locations (Excel file)

Google Map - All Locations

NAC Attack Funder

National Eye Institute – National Institutes for Health

Supporting Organizations

Zambon SpA, Milan, Italy
Usher 2020
Fighting Blindness Canada
Retina UK

NAC Attack Leadership

Study Chairman's Office

Study Chair: Peter Campochairo, M.D.
Vice Chair: Mandeep Singh, M.B.B.S., M.D., Ph.D.
Vice Chair: Rupert Strauss, M.D.
Gulnar Hafiz
Dagmar Wehling

Coordinating Center

Director and Senior Biostatistician: Xiangrong Kong, Ph.D.
Informatics Director: Kurt Dreger
Project Coordinators: Bhavishya Pancharathi and Chrisanthe Papapavlou
Finance: Simone Butler and Lee Rorke
Research Fellow: Folahan Ibukun
Research Assistant: Guoshu Kong

NAC Attack Data Safety Monitoring Committee (DSMC)

Chair: Steven Piantadosi, M.D., Ph.D.
Biostatistics and Oncology, Brigham and Women's Hospital, Harvard University

Elise Heon, M.D.
Ophthalmology and Vision Sciences, University of Toronto

Judith Hochman, M.D.
Cardiology and Clinical Trials, New York University

David C. Musch Ph.D., M.P.H.,
Epidemiology and Ophthalmology, University of Michigan

Stephen H. Tsang, M.D., Ph.D.
Ophthalmology, and Pathology and Cell Biology, Columbia University

David N. Zacks, M.D., Ph.D.
Ophthalmology and Visual Sciences, University of Michigan

Alison Bateman-House, Ph.D.
Population Health, New York University

About Wilmer

Education Opportunities

100 Years of Wilmer

NAC Attack: A Multicenter, Placebo-Controlled Clinical Trial To Test Oral N-Acetylcysteine in Patients

NAC Attack Investigative Group Meeting

A Team Effort!

Meeting Registration

Participants at the Friday Night Banquet Dinner!

NAC Attack Investigative Group Meeting February 1, 2025​

Xiangrong Kong: NAC Attack Coordinating Center Director and Senior Biostatistician

OCT Reading Center, Duke University

Muhammad Jehanzeb Khan, Study Chair's Office​, Johns Hopkins University, Wilmer Eye Institute​

Yuki Wiland, Harvard University

Raymond Lezzi, Mayo Clinic

Hailey Ahrens, Vitreo Retinal Associates

Mariana Edwards and Kimberly Rodriguez, University of Southern California

Zainab Rustam, ​Study Chair’s Office​, Johns Hopkins University, Wilmer Eye Institute

Alexandra Versleijen, Radboud University, the Netherlands​

Rupert Strauss, Medical University Graz, Austria​

Petra Rossouw​, University of Basel, Switzerland

Laura Kuehlewein​, University of Tubingen, Germany​

Ronald van Leersum, Amsterdam University, the Netherlands​

Research presentation​, Izzie Wang, NAC Attack Coordinating Center, Johns Hopkins University

Research presentation,​ Alyssa Bonnell and Jennifer Chao,​ University of Washington

Milam Brantley, Vanderbilt University

Shivani Kochhar, University of Florida

Mary McCormick, University of Iowa

Adriana Padilla Drada, University of Miami

Grace Trigler, University of Oklahoma

Research Presentation, Hossein Ameri, University of Southern California

Meaghyn Kramer, University of Minnesota

Daphné Doucet, McGill University

Callie Gordon, University of Michigan

Lorraine Almeda, Stanford University

Denise Macias, University of California Davis

Rob Hufnagel, Kaiser Permanente Hawaii

Rodrigo Matsui Serrano, Instituto de Oftalmología Fundación Conde de Valenciana, Mexico

Fred Collison, Northwestern University

Susie Trotochaud, USHER 2020 Foundation

Joseph Kreis, Medical College of Wisconsin, AOSLO Reading Center

David Birch, Retina Foundation of the Southwest

Nancy Aychoua, Moorfields Eye Hospital, University College London

Alexandra Garafalo, University of Pennsylvania

Nicole Boone and Nickie Stangel, University of Wisconsin, Madison

Katie McKenney, Medical College of Wisconsin

Jenna Huey, University of Washington

Jianrong Shen, University of Illinois, Chicago

Paul Bernstein, University of Utah

Nieraj Jain, Emory University

Folahan Ibukun, NAC Attack Coordinating Center, Johns Hopkins University

NAC Attack Study News

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

NAC Attack at ARVO

Frequently Asked Questions

What is Retinitis Pigmentosa?

What is NAC?

What is NAC Attack and why is it needed?

Why is a randomized, placebo-controlled trial, and double masked trial needed?

I see NAC is available in the drug store. Should I just buy it and start taking it?

When will we know NAC Attack study results?

NAC Attack Video FAQ

Clinical Sites

NAC Attack Funder

Supporting Organizations

NAC Attack Leadership

Study Chairman's Office

Coordinating Center

NAC Attack Data Safety Monitoring Committee (DSMC)

Contact Us Email

NAC Attack Investigative Group Meeting February 1, 2025

Muhammad Jehanzeb Khan, Study Chair's Office, Johns Hopkins University, Wilmer Eye Institute

Zainab Rustam, Study Chair’s Office, Johns Hopkins University, Wilmer Eye Institute

Alexandra Versleijen, Radboud University, the Netherlands

Rupert Strauss, Medical University Graz, Austria

Petra Rossouw, University of Basel, Switzerland

Laura Kuehlewein, University of Tubingen, Germany

Ronald van Leersum, Amsterdam University, the Netherlands

Research presentation, Izzie Wang, NAC Attack Coordinating Center, Johns Hopkins University

Research presentation, Alyssa Bonnell and Jennifer Chao, University of Washington