Apr 12, 2024

Phase 3 Clinical Trial of NAC Launched for RP Patients

Eye On the Cure Research News

The drug is thought to work independent of the mutated gene causing RP.

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Johns Hopkins University (JHU) has launched a Phase 3 clinical trial of N-acetylcysteine (NAC) for the treatment of retinitis pigmentosa (RP). Known as NAC Attack, the 45-month study is enrolling approximately 438 patients at 30 sites throughout the US, Canada, Mexico, and Europe. Study participants will be assigned randomly 2:1 to either the treatment or placebo group, respectively. If the NAC group shows benefit (i.e., slowing of vision loss) at 21 months, participants in the placebo group will begin to receive the treatment.

JHU’s Peter Campochiaro, MD, and Xiangrong Kong, PhD, designed the trial and are its lead investigators.

The National Eye Institute is providing more than $20 million in funding for NAC Attack.

NAC is an oral antioxidant approved in 1963 by the US Food & Drug Administration for acetaminophen (Tylenol®) overdose.  It is also used for treating cystic fibrosis and pulmonary diseases.

In normal retinas, the amount of oxygen delivered to the retina is equal to the amount consumed by cells. Dr. Campochiaro says that after many rod photoreceptors are lost in RP patients, the amount of oxygen exceeds the amount consumed. This leads to over-production of reactive oxygen species (ROS), byproducts of oxygen processing. Dr. Campochiaro says ROS are damaging to cone photoreceptors when produced in excess.

NAC slowed retinal degeneration in Foundation-funded animal studies of RP. Researchers believe the drug can work independent of the mutated gene causing RP.

In the six-month, 30-patient Fight RP clinical trial, investigators determined the highest tolerable dose of NAC. Small improvements in vision were also observed for people receiving the highest dose.

Dr. Campochiaro strongly recommends that people not take NAC outside of the clinical trial, because researchers don’t know yet if long term treatment with NAC provides any benefit in RP or whether there are disadvantages such as side effects. This is what NAC Attack will determine.

Dr. Campochiaro says that patients with RP could consider joining the trial and being monitored closely for both good and bad effects, or simply waiting for the results of the trial to be well-informed on the potential risks and benefits of taking NAC, how it should be taken, and how they should be monitored if they take the drug. Taking any drug or supplement without supervision of a physician is potentially hazardous, and what is sold as NAC supplements is unregulated, so the exact content is unknown.  

Questions about the trial can be sent to NACAttack@jh.edu.

Nacuity Pharmaceuticals is conducting a Phase 2 clinical trial in Australia of NACA for people with Usher syndrome. NACA is a modified form of NAC that is designed to be more potent and bioavailable to the retina. The RD Fund, the Foundation’s venture philanthropy arm, is an original investor in Nacuity.