RESEARCH TRIANGLE PARK, N.C., July 9, 2026
Opus Genetics announced an important clinical development update for its Phase 1/2 BIRD-1 clinical trial evaluating OPGx-BEST1, an investigational AAV-based gene therapy designed to treat BEST1-associated inherited retinal diseases (IRDs). The company confirmed that three-month topline data from Cohort 1 are expected during the second week of September 2026, assuming all participants complete scheduled assessments. The results are also planned for presentation at the EURETINA Congress 2026 in Vienna from October 1–4, 2026. OPGx-BEST1 is being developed as a one-time gene therapy intended to restore BEST1 gene function and address the underlying genetic cause of retinal degeneration in patients with Best Vitelliform Macular Dystrophy (BVMD) and Autosomal Recessive Bestrophinopathy (ARB), conditions for which no approved therapies currently exist.
Phase 1/2 BIRD-1 Trial Advances Toward Key Clinical Milestone
The BIRD-1 study is an adaptive, open-label, Phase 1/2 dose-escalation clinical trial evaluating the safety, tolerability, and preliminary efficacy of a single subretinal administration of OPGx-BEST1 in adult patients with BEST1-associated retinal diseases. Cohort 1 enrollment was completed in May 2026, enrolling five participants, including three patients with BVMD and two with ARB. Before enrollment, BVMD participants underwent additional laboratory testing using an in vitro mutation assessment platform to confirm that their disease-causing mutations were suitable for gene augmentation therapy.
Following completion of the three-month evaluation period, an Independent Data Monitoring Committee (IDMC) will review the complete dataset and determine whether the study should advance to the higher-dose Cohort 2. The trial is evaluating two dose levels, beginning with 1.5E9 vg/eye in Cohort 1 followed by 4.5E9 vg/eye in Cohort 2, to optimize dose selection and future clinical development.
Structural and Functional Endpoints Will Guide Future Development
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The primary objective of the first cohort is to evaluate the safety and tolerability of OPGx-BEST1, while also measuring multiple structural and functional indicators of retinal improvement. Investigators will closely monitor subretinal fluid using Optical Coherence Tomography (OCT), with reductions in fluid serving as evidence of biological target engagement. According to Opus Genetics, approximately 20% reduction in subretinal fluid may represent a clinically meaningful response supporting progression into Cohort 2, while complete fluid resolution in the majority of participants could potentially justify discussions with the U.S. Food and Drug Administration (FDA) regarding expansion into a pivotal clinical trial.
In parallel, investigators will evaluate several vision-related functional endpoints, including Best Corrected Visual Acuity (BCVA), Low Luminance Visual Acuity (LLVA), contrast sensitivity, and microperimetry. Demonstrating improvements across both structural imaging and visual function would strengthen evidence that the investigational therapy is providing clinically meaningful benefit. Due to the open-label design of the study, the company also announced it will enter an investor relations quiet period beginning July 15, 2026, until the public release of topline data.
OPGx-BEST1 Aims to Address Significant Unmet Need in Rare Retinal Diseases
OPGx-BEST1 utilizes Opus Genetics’ proprietary adeno-associated virus (AAV) gene therapy platform to deliver a functional copy of the BEST1 gene directly to retinal pigment epithelium (RPE) cells, where disease-causing mutations impair retinal function. Preclinical research demonstrated restoration of BEST1 protein expression and improvements in retinal function, supporting advancement into clinical testing. The company estimates that approximately 21,800 patients worldwide, including roughly 8,400 individuals in the United States, are affected by BEST1-associated inherited retinal diseases, highlighting the substantial unmet medical need for disease-modifying therapies.
Chief Executive Officer George Magrath, M.D., noted that patient interest in the study has remained strong and additional participants have already been identified for possible enrollment into Cohort 2 if the trial advances as planned. With September 2026 now established as the anticipated timeframe for the first topline clinical results, Opus Genetics continues to advance its gene therapy pipeline aimed at delivering durable, one-time treatments capable of restoring vision and slowing retinal degeneration in patients with inherited eye diseases.
Source:Opus Genetics press release
