May 07, 2026 —
Opus Genetics announced the completion of enrollment in Cohort 1 of its ongoing Phase 1/2 study evaluating OPGx-BEST1, an investigational AAV-based gene therapy for BEST1-associated inherited retinal diseases. The study includes adult participants with both Best Vitelliform Macular Dystrophy (BVMD), the dominant form of BEST disease, and Autosomal-Recessive Bestrophinopathy (ARB), the recessive form.
The adaptive, open-label trial is designed to evaluate the safety and efficacy of single-eye subretinal administration of OPGx-BEST1 at up to two dose levels. A total of five participants have been enrolled in Cohort 1, including three with BVMD and two with ARB. Four participants have already been dosed, and the fifth participant is scheduled to undergo dosing this month.
OPGx-BEST1 uses Opus Genetics’ proprietary AAV-based gene therapy platform to deliver a functional copy of the BEST1 gene directly to retinal pigment epithelium (RPE) cells, where the defective gene resides. BEST1-associated inherited retinal diseases affect an estimated 22,000 patients worldwide and currently have no approved treatments. By restoring BEST1 function, the therapy aims to address the underlying genetic cause of retinal degeneration and help preserve photoreceptor health and visual function.
At the ARVO Annual Meeting, principal investigator Mark Pennesi, M.D., Ph.D., presented baseline demographics for Cohort 1, along with three-month results from the first sentinel participant. According to Opus, early findings showed positive tolerability and biological activity following subretinal administration of OPGx-BEST1.
For participants with the dominant form of BEST disease, Opus also used an in vitro platform to confirm that each participant’s disease-causing mutation was amenable to gene augmentation. This additional step is important because dominant retinal diseases can present unique development challenges, and confirming gene augmentation potential may help refine patient selection.
Opus expects to announce three-month topline data from the full Cohort 1 in September 2026, with additional data to be presented at an ophthalmology medical conference later this year. Planned outcome measures include structural optical coherence tomography (OCT), microperimetry, best-corrected visual acuity, low-luminance visual acuity, and contrast sensitivity.
The completion of Cohort 1 enrollment marks an important clinical milestone for OPGx-BEST1 and highlights continued progress in developing AAV gene therapies for inherited retinal diseases, particularly for conditions with no approved treatment options.
