Opus Genetics has reported early findings from its ongoing Phase I/II clinical trial of the OPGx-BEST1 gene therapy for the treatment of best vitelliform macular dystrophy (BVMD) and autosomal-recessive bestrophinopathy (ARB).

These outcomes were presented at the 49th annual meeting of the Macula Society in San Diego, California, US. The presentation included data from a 63-year-old female participant with ARB.

After three months, OPGx-BEST1 was observed to be well tolerated with no ocular inflammation, adverse events or dose-limiting toxicities reported.

Early signs of functional improvement were recorded, including a 12-letter gain in best corrected visual acuity (BCVA) in the treated eye. Central subfield thickness in the study eye decreased by 23%, and intraretinal fluid resolved within one month in areas with less atrophy.

The open-label, adaptive Phase I/II study involves administering a single subretinal injection of OPGx-BEST1 to one eye per participant, across two dosing cohorts for adult participants who have BVMD or ARB.

The main aim is to assess the safety and tolerability, determine the optimal dose for further development, and monitor long-term outcomes alongside biological activity through functional and anatomical endpoints.

Opus Genetics CEO George Magrath said: “We are encouraged by these results from our sentinel participant, showing OPGx-BEST1 was well-tolerated and demonstrated promising initial efficacy at three months.

“Although early, this data represents an important milestone for our OPGx-BEST1 programme and for patients with BEST1-related retinal diseases.”

Recruitment continues at two US sites, with more locations planned in Cincinnati, Florida and New York. Two participants are currently enrolled. Three-month results from the full Cohort 1 are expected in mid-2026.

In November 2025, Opus Genetics dosed the first subject in its Phase I/II clinical trial of OPGx-Best1 as a treatment for Best disease (BEST1).