Aura Biosciences has announced positive results from its Phase 2 trial evaluating bel-sar (AU-011) as a first-line treatment for early-stage choroidal melanoma (CM). The study, an open-label, ascending dose escalation trial, assessed the safety, tolerability, and efficacy of bel-sar in patients with small CM and indeterminate lesions. The results were presented at The Retina Society Annual Meeting in Lisbon, Portugal.
Promising Tumor Control and Vision Preservation
The Phase 2 trial, which enrolled 22 patients, demonstrated an 80% tumor control rate among Phase 3-eligible patients who received the therapeutic regimen. Notably, the treatment led to a complete cessation of tumor growth in responders, with the post-treatment average growth rate at 0.011 mm/year compared to 0.351 mm/year prior to the study (p<0.0001). Visual acuity preservation was achieved in 90% of these patients. According to Aura Biosciences, 80% of these patients were at high risk for vision loss due to the proximity of tumors to the fovea or optic disc.
Favorable Safety Profile
Bel-sar exhibited a favorable safety profile across all participants, with no treatment-related serious adverse events reported. Mild, Grade 1 ocular treatment-related adverse events, including anterior chamber inflammation (18%) or cell (9%), resolved without sequelae. Most inflammation events were self-limited, resolving in a median of 6 days, while others required short-duration topical steroid treatment. No treatment-related posterior inflammation events were reported.
Expert Commentary
Dr. Ivana Kim, Director of the Ocular Melanoma Center at Mass Eye and Ear/Harvard Medical School, noted that bel-sar has the potential to achieve the dual goals of treating the tumor while preserving vision, potentially changing the treatment paradigm for patients with this disease. Dr. Jill Hopkins, Chief Medical Officer and President of Research and Development at Aura Biosciences, added that the Phase 2 results provide clinical evidence for bel-sar as a potential vision-sparing, first-line treatment option for early-stage CM.
Mechanism of Action
Bel-sar consists of virus-drug conjugates (VDCs) activated by light to target tumors. The VDCs selectively bind to heparin sulfate proteoglycans on tumor cells and are coated with a photosensitizer that generates reactive oxygen species upon activation by infrared light, damaging tumor cell membranes and leading to cell death. The body’s immune system is also activated to further target and destroy the tumor.
Next Steps
Aura Biosciences has initiated a Phase 3 trial for bel-sar and is exploring the potential of VDCs to target bladder tumors. The company has received written agreement from the FDA under a Special Protocol Assessment for the design and planned analysis of the Phase 3 trial, indicating concurrence by the FDA with the adequacy of the study to support Aura’s planned biologics license application submission. The Phase 3 trial is expected to conclude in 2026.
