Phase 3 clinical trial of NAC launched for RP patients

Key Takeaways

• A Phase 3 clinical trial has been launched to test the viability of N-acetylcysteine (NAC) in slowing retinitis pigmentosa (RP).
• NAC is believed to work independent of the mutated gene causing RP.

Johns Hopkins University has launched a Phase 3 clinical trial of N-acetylcysteine (NAC) for the treatment of retinitis pigmentosa (RP), a genetic disease that causes the retina to slowly break down over time. 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 in a 2:1 ratio 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.

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. Co-lead investigator Dr. Peter Campochiaro says that after many rod photoreceptors are lost in RP patients, the amount of oxygen exceeds the amount consumed. This leads to overproduction of reactive oxygen species (ROS), byproducts of oxygen processing. ROS are damaging to cone photoreceptors when produced in excess. NAC functions as an ROS inhibitor.

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

Dr. Campochiaro strongly recommends that people not take NAC outside of the clinical trial. The NAC Attack will determine if long term treatment with NAC provides benefit in RP or whether there are any adverse side effects. For more information about the trial, visit https://clinicaltrials.gov/study/NCT05537220, or contact Dagmar Wehling, COA, CCRP, by emailing  NACAttack@jh.edu or calling 410-502-7621.

Edited by Suditi Kedambadi and Miriam Kaplan, PhD

Source: Foundation Fighting Blindness, Eye on the Cure Research News, April 12, 2024; see source article