Nacuity Pharmaceuticals Reports Positive Clinical Trial Results For NPI-001 In Treating Retinitis Pigmentosa Linked To Usher Syndrome

Nacuity Pharmaceuticals, Inc., a clinical-stage biopharmaceutical company focused on developing innovative treatments for eye diseases caused by oxidative stress, has announced new and positive results from its SLO-RP Phase 1/2 clinical trial. The trial evaluated NPI-001 tablets for treating patients with retinitis pigmentosa (RP) associated with Usher syndrome (USH), a rare genetic disorder that causes progressive vision and hearing loss.

According to Halden Conner, Chairman, CEO, and Co-Founder of Nacuity, the results provide important clinical validation that NPI-001 can slow the loss of photoreceptors in patients with RP linked to USH. He added that the findings will be used to design a confirmatory study, which Nacuity plans to begin in 2026. Conner described this development as a key step toward moving NPI-001 closer to approval for a patient population with limited treatment options.

The SLO-RP core trial was a randomized, placebo-controlled, multicenter study conducted at four clinical sites in Australia. A total of 49 patients participated, receiving either NPI-001 or placebo tablets taken orally twice a day over a two-year period. Researchers assessed the health of photoreceptors by measuring Ellipsoid Zone (EZ) Area using SD-OCT imaging. Retinal sensitivity, an indicator of functional vision, was measured using MAIA microperimetry. The database lock for the trial was completed in June 2025.

The study found that NPI-001 slowed photoreceptor loss by more than 50 percent over two years. The benefits began as early as six months after treatment and continued throughout the 24-month period. Although retinal sensitivity did not achieve statistical significance at 24 months, a positive trend was observed, with NPI-001-treated participants showing nearly 30 percent slower decline in visual function compared to placebo. The effects on EZ area and retinal sensitivity were found to be closely linked. NPI-001 was also shown to be safe and well tolerated at a dose of 500 mg per day, and more than 80 percent of participants adhered to the planned dosing schedule.

Jami Kern, Ph.D., Senior Vice President and Chief Clinical Officer of Nacuity, stated that current treatments for RP benefit only a small fraction of patients facing progressive vision loss. These findings, she said, strengthen NPI-001’s potential as a much-needed therapy for the wider RP community. Mark Pennesi, MD, Ph.D., Director of Ophthalmic Genetics at the Retina Foundation of the Southwest in Dallas, Texas, highlighted that NPI-001 is the only small molecule drug to show a measurable treatment effect for RP to date. He described the results as initial proof of concept for treating RP and emphasized the value of NPI-001 as a gene-agnostic therapy.

Nacuity has been collaborating with the Foundation Fighting Blindness on several initiatives related to NPI-001’s development, including trial design, raising awareness, educational efforts, and strategic guidance. The Foundation has also provided funding support through its venture arm, the Retinal Degeneration Fund (RD Fund). Rusty Kelly, Ph.D., Managing Director of the RD Fund, expressed encouragement over the data showing preservation of the EZ area and said the Foundation is eager to confirm these findings in a future registrational trial.