Opus Genetics reports visual and retinal improvements with OPGx-BEST1 in Phase 1/2 BIRD-1, supporting pivotal development in BEST1-related retinal disease.
Written By: Saniya Katakdhond, PharmD
Reviewed By: Pharmacally Editorial Team
Opus Genetics reported positive 3- and 6-month results from Cohort 1 of the Phase 1/2 BIRD-1 trial of OPGx-BEST1 (NCT07185256), an investigational gene therapy for BEST1-related retinal diseases. All five treated patients showed clinically meaningful improvement in at least one measure of visual function, while four showed structural retinal improvements, supporting further development into pivotal testing.
Functional Gains Across Multiple Vision Measures
BIRD-1 is evaluating a single subretinal administration of OPGx-BEST1 in adults with Best vitelliform macular dystrophy (BVMD) or autosomal recessive bestrophinopathy (ARB). Cohort 1 included three patients with BVMD assessed at three months and two patients with ARB assessed at six months, all treated at 1.5 × 10⁹ vector genomes per eye.
Across the five participants, clinically meaningful improvement occurred in best-corrected visual acuity (BCVA), low-luminance visual acuity, contrast sensitivity or microperimetry. BCVA improved in three patients, while two improved in both low-luminance visual acuity and contrast sensitivity. Among four evaluable participants, three showed clinically meaningful improvement in retinal sensitivity on microperimetry.
The functional gains were concentrated in the retinal pigment epithelium (RPE) transitional zone, where viable but compromised photoreceptors remain. Patients with less advanced disease showed the greatest improvements, suggesting that preserved retinal tissue may be important for treatment response.
Structural Retinal Improvements
Structural changes also supported the functional findings. Four of five participants showed retinal structural improvement. In BVMD, reductions in vitelliform material occurred in two of three patients. In ARB, both treated patients showed reductions in intraretinal fluid.
The distinction is clinically relevant because vitelliform material is the defining early structural feature of BVMD and reflects dysfunction of the RPE, whereas intraretinal fluid is a dominant manifestation of ARB. The company reported that reductions in vitelliform material corresponded with functional improvement in the BVMD participants who showed the structural change.
Favorable Early Safety Profile
OPGx-BEST1 showed a favorable safety and tolerability profile in Cohort 1. No serious adverse events or dose-limiting toxicities were reported, and investigators observed no intraocular inflammation or notable abnormalities in vital signs or safety laboratory tests. Treatment-related adverse events were mild or moderate.
OPGx-BEST1 uses an adeno-associated virus (AAV) vector to deliver a functional copy of BEST1 to retinal pigment epithelial cells. BEST1 mutations impair RPE function and can cause progressive retinal degeneration and vision loss in diseases including BVMD and ARB. No approved therapy currently addresses the underlying genetic cause.
FDA Alignment Supports Pivotal Development
The regulatory path also advanced in August 2026, when Opus Genetics met with the FDA to discuss pivotal development. The company said it aligned with the agency on a potential endpoint combining at least a 3-dB improvement in microperimetry at five prespecified loci with a patient-reported outcome in a randomized, controlled trial. BCVA, low-luminance visual acuity and contrast sensitivity could also serve as endpoints.
The company plans to complete Phase 3 and commercial manufacturing requirements in early 2027 and expects participant dosing in a potential pivotal trial to begin later that year.
Higher-Dose Cohort Underway
Opus Genetics has advanced BIRD-1 to Cohort 2 at a higher dose of 4.5 × 10⁹ vg/eye. The cohort expanded from five planned participants to eight because of rapid enrollment, with most participants having BVMD. Dosing is expected to finish in the fourth quarter of 2026, with topline three-month data anticipated in the second quarter of 2027.
The next dataset should help determine whether the higher dose produces consistent functional and structural responses and will inform the design of the potential pivotal study. The company also expects to report six-month data from the three Cohort 1 BVMD participants in the second quarter of 2027.
Reference
Opus Genetics Announces Positive Low Dose Cohort 1 Data from Phase 1/2 Clinical Trial of OPGx-BEST1 and Successful FDA Type C Meeting with Potential Phase 3 Dosing in 2027, Opus Genetics, 09 September 2026
About the Writer
Saniya Sanjay Katakdhond (Linkedin) is a Doctor of Pharmacy professional with hands-on experience in patient case review, clinical documentation, medical record analysis, and patient care.
Her hospital experience has strengthened her understanding of clinical conditions, treatment approaches, and multidisciplinary healthcare practices.
With ICH-GCP certification and a research-oriented approach, she brings clinical insight and attention to detail to healthcare content development.
As a healthcare writer, Saniya focuses on translating clinical knowledge and patient-care experience into clear, accurate, and evidence-informed medical content.