Opus Genetics reports positive Phase 1/2 OPGx-BEST1 data
Opus Genetics has reported positive 3- and 6-month data from Cohort 1 of its BIRD-1 Phase 1/2 trial, evaluating OPGx-BEST1 in patients with BEST1-related inherited retinal diseases. All five participants treated at the low dose showed clinically meaningful improvements in visual function, and the company said it expects to begin Phase 3 participant dosing in 2027.
OPGx-BEST1 is an AAV-based gene therapy designed to deliver a functional copy of the BEST1 gene to retinal pigment epithelial cells, addressing the underlying genetic cause of Best vitelliform macular dystrophy (BVMD) and autosomal recessive bestrophinopathy (ARB). No approved therapies currently target the root genetic defect in either condition.
Cohort 1 results
The five Cohort 1 participants received a dose of 1.5 x 10⁹ viral genomes per eye. Best-corrected visual acuity improved in three of five participants, while three of four evaluable participants showed clinically meaningful gains in retinal sensitivity by microperimetry. Structural improvements, including reductions in vitelliform material in BVMD and intraretinal fluid in ARB, were observed in four of five participants. The company noted that the greatest functional gains occurred in participants with less advanced disease, suggesting earlier intervention may yield stronger outcomes.
The safety profile was clean: no serious adverse events, no dose-limiting toxicities, no intraocular inflammation, and all treatment-related adverse events were mild or moderate. In August 2026, Opus met with the FDA under a Type C meeting and reached alignment on a potential pivotal endpoint of a 3 dB or greater improvement in microperimetry across at least five prespecified loci, in conjunction with a patient-reported outcome measure, in a randomised controlled trial.
Mark Pennesi, clinical trial investigator and Chief Medical Officer at the Retina Foundation, said it was "particularly exciting to align with the FDA on a greater-than-3 decibels change from baseline in microperimetry anchored to patient reported outcomes as a potential pivotal endpoint."
Pipeline and market context
Encouraged by these early results, the company has advanced to Cohort 2, testing a threefold higher dose of 4.5 x 10⁹ viral genomes per eye. Cohort 2 has over-enrolled at eight participants against an original target of five; dosing is expected to complete in Q4 2026, with topline three-month data anticipated in Q2 2027. Opus said it expects its cash runway to extend into 2029, providing headroom through multiple clinical inflection points.
New epidemiology work commissioned from Triangle Insights Group, based on a survey of more than 150 eye care professionals, now estimates approximately 23,600 symptomatic BEST1 patients in the United States and around 45,400 globally, a materially larger figure than the company had previously assumed. The undiagnosed fraction, estimated at roughly 10,600 in the US alone, points to a potential opportunity for expanded newborn or genetic screening programmes.
The inherited retinal disease space has attracted growing attention from both large pharma and specialist gene therapy developers. Spark Therapeutics' Luxturna, approved for RPE65-associated retinal dystrophy, established the regulatory template for subretinal gene therapy and demonstrated willingness at the FDA to accept functional vision endpoints in small patient populations, a precedent that should support Opus's microperimetry-anchored endpoint strategy. Opus also flags the potential to qualify for FDA priority review vouchers given the rare paediatric disease designation pathway, which could have meaningful balance-sheet implications if and when a pivotal programme succeeds.
The next catalysts to watch are Cohort 2 topline data in mid-2027 and the formal Phase 3 trial design, which Opus said it plans to finalise once manufacturing requirements are confirmed in early 2027.