Nacuity Pharmaceuticals reports that, in an early stage clinical trial, its oral formulation of N-acetylcysteine amide (NPI-001) slowed disease progression in patients with retinitis pigmentosa (RP) associated with Usher syndrome. Treatment with NPI-001 reduced ellipsoid zone (EZ) area loss by more than 50% over 2 years, compared to placebo, the company said in a press release.

SLO-RP is a randomized, placebo-controlled, multicenter phase 1/2 study conducted at 4 sites in Australia. Forty-nine patients received oral NPI-001 (500 mg/day) or placebo twice daily for 24 months. The treatment effect was evident by 6 months and sustained through the study period. Retinal sensitivity did not meet statistical significance at 24 months, but patients receiving NPI-001 demonstrated nearly 30% slower decline and outcomes correlated closely with EZ preservation.

NPI-001 was well tolerated, with no persistent drug-related adverse events and more than 80% treatment adherence. Investigators described the results as initial proof of concept for a small-molecule therapy in RP. The company says the data will guide the design of a confirmatory registrational study, which it expects to initiate in 2026.