Darovasertib Phase 2 Results Show Robust Tumor Shrinkage and Vision Preservation in Uveal Melanoma
83% of Patients Achieved Tumor Shrinkage—Potentially Shifting the Treatment Landscape
IDEAYA Biosciences has unveiled encouraging results from its Phase 2 OptimUM-09 trial evaluating darovasertib in patients with primary uveal melanoma. Among 94 evaluable patients, an impressive 83% experienced ocular tumor shrinkage, with over half (54%) seeing a reduction of at least 20% in tumor size. These data, presented at the 2025 ESMO Congress, come amid a clear need for systemic therapies that can delay or prevent the loss of vision—and even the eye itself—in this rare and challenging cancer.
Eye and Vision Preservation: Results at a Glance
Eye preservation remains a critical concern in uveal melanoma. The study found a 57% eye preservation rate among patients for whom enucleation (eye removal) was recommended—a figure that soared to 95% in those who achieved =20% tumor shrinkage. Patients eligible for plaque brachytherapy (PB) also benefited, with 70% showing a reduced predicted radiation dose and 65% projected to have a lower risk of significant vision loss at three years post-treatment.
| Measure | Key Finding |
|---|---|
| Tumor Shrinkage (Any Amount) | 83% (78/94 patients) |
| =20% Tumor Shrinkage | 54% (51/94 patients) |
| Eye Preservation (EN-Recommended) | 57% (24/42 patients); 95% (19/20 with =20% shrinkage) |
| Reduction in Radiation Dose (PB Eligible) | 70% (26/37 patients) |
| Lower Predicted Risk of Vision Loss (PB Eligible) | 65% (24/37 patients) |
| Improved Visual Acuity Score (VAS) | 55% (EN Eligible), 61% (PB Eligible) |
| Mean Gain in Visual Acuity Letters | 17 (EN), 10 (PB) |
Key Study Insights: Visual and Radiation Benefits
Beyond preserving the physical eye, darovasertib treatment translated into functional gains: over half of both EN-eligible and PB-eligible patients improved their visual acuity during therapy, with average letter score gains of 17 and 10, respectively. For patients undergoing PB, about 70% achieved a reduction in predicted radiation to critical eye structures, which may directly impact the risk of future vision loss. The significance of even a 20% reduction in radiation dose is supported by published outcomes linking such decreases to better long-term visual function.
Favorable Safety and Tolerability Profile Supports Ongoing Trials
The safety profile was manageable—grade 3 or higher treatment-related adverse events occurred in 16.8% of patients, and the rates of treatment discontinuation (6.3%) and serious adverse events (5.3%) remained low. Common adverse effects were mostly low grade and included diarrhea, nausea, vomiting, and fatigue.
Outlook: Toward First-Line Systemic Therapy for Uveal Melanoma
With no approved systemic treatments for primary uveal melanoma, darovasertib is now under investigation in a Phase 3 trial using =20% tumor shrinkage as the definition of response. IDEAYA’s leadership notes the potential to set a new treatment paradigm, with further pivotal data expected from additional ongoing studies, including a Phase 2/3 trial combining darovasertib with crizotinib.
Takeaway for Readers
For patients and investors tracking innovation in oncology, these Phase 2 results are a clear signal that systemic therapy for primary uveal melanoma could soon be within reach. Darovasertib’s potential to spare vision—and eyes—may well change the trajectory of care in this high-need population. As Phase 3 and registration-enabling trials progress, stakeholders will be watching closely to see if these benefits are confirmed and extended to broader patient groups.
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