Oculis completes final patient visit in OCS-01 phase 3 trial in DME

Oculis Holding AG announced that the final patient visit has been completed in the DIAMOND phase 3 program assessing OCS-01, an investigational high-concentration dexamethasone eye drop, in patients with diabetic macular edema (DME). Topline results from the 52-week trials are expected in June 2026, with a potential US regulatory submission anticipated later in the year. The absence of available data at this stage limits conclusions regarding clinical benefit or comparative effectiveness.

Trial overview

The DIAMOND program consists of 2 multicenter, randomized, double-masked phase 3 trials (DIAMOND-1 and DIAMOND-2) enrolling more than 800 patients with DME. Participants were randomized 1:1 to receive either OCS-01 or vehicle control. The dosing regimen included an intensive induction phase (6 times daily for 6 weeks), followed by maintenance dosing (3 times daily through week 52).

The primary endpoint is mean change in best-corrected visual acuity (BCVA), measured by Early Treatment Diabetic Retinopathy Study (ETDRS) letter score, at week 52. Secondary endpoints include the proportion of patients achieving a ≥15-letter gain and change in central subfield thickness (CST), reflecting anatomic response.

These trials were initiated based on earlier-stage data from the DIAMOND program suggesting improvements in visual acuity and retinal thickness; however, those findings have not been fully characterized in peer-reviewed publications, limiting independent assessment.

Clinical context

DME remains a leading cause of vision impairment among working-age adults with diabetes. Current standard-of-care therapies primarily include intravitreal anti–vascular endothelial growth factor (VEGF) agents such as aflibercept, ranibizumab, and off-label bevacizumab, as well as corticosteroid implants.^1–3 While these therapies have demonstrated efficacy, they require repeated intravitreal injections, contributing to treatment burden and adherence challenges.

Real-world data suggest substantial gaps in treatment delivery. Analysis from the American Academy of Ophthalmology IRIS Registry indicates that a significant proportion of patients with newly diagnosed DME remain untreated within the first year.⁴ Additionally, randomized trial data from the DRCR Retina Network Protocol I study demonstrated that a meaningful subset of patients exhibit suboptimal visual response despite anti-VEGF therapy.²

These limitations have prompted ongoing investigation into alternative delivery modalities and adjunctive approaches, including sustained-release implants and topical formulations targeting inflammatory pathways.

Drug background and mechanism

OCS-01 is a topical formulation of dexamethasone designed using a proprietary solubilizing platform intended to enhance drug penetration to the posterior segment. Corticosteroids are known to reduce vascular permeability and inflammation, both of which contribute to the pathophysiology of DME.⁵

Currently approved corticosteroid options for DME, such as dexamethasone intravitreal implants, provide sustained intraocular drug delivery but are associated with procedure-related risks and adverse effects, including intraocular pressure elevation and cataract formation.³ A topical alternative, if effective, could reduce procedural burden, though achieving therapeutic drug levels in the retina via topical administration has historically been challenging.

Interpretation and unanswered questions

The completion of the DIAMOND trials represents a developmental milestone; however, the clinical relevance of OCS-01 will depend on whether the forthcoming data demonstrate meaningful improvements in visual acuity and retinal anatomy compared with control.

Key considerations include the magnitude and durability of the treatment effect, the safety profile—particularly steroid-associated adverse events—and the real-world feasibility of the relatively frequent dosing regimen. Additionally, comparison with existing therapies, either directly or indirectly, will be important in determining the potential role of OCS-01 in treatment algorithms.

Notably, no phase 3 data are yet available in the public domain, and earlier-stage results have not been extensively validated in peer-reviewed literature. As such, independent verification of efficacy and safety outcomes will be essential.

Limitations and next steps

The primary limitation at this stage is the absence of published efficacy and safety results from the phase 3 trials. Without these data, the therapeutic value of OCS-01 remains uncertain. Furthermore, the feasibility of long-term adherence to a multiple-times-daily eye drop regimen in a chronic retinal disease population warrants consideration.

If positive, the DIAMOND results could support a regulatory submission and potentially expand the therapeutic landscape for DME. Future analyses should also explore subgroup responses, combination therapy potential, and comparative effectiveness against established anti-VEGF agents.

References

1. Diabetic Retinopathy Clinical Research Network. Aflibercept, bevacizumab, or ranibizumab for diabetic macular edema. N Engl J Med. 2015;372(13):1193-1203.
   https://www.nejm.org/doi/full/10.1056/NEJMoa1414264

2. Elman MJ, Aiello LP, Beck RW, et al; Diabetic Retinopathy Clinical Research Network. Randomized trial evaluating ranibizumab plus prompt or deferred laser for diabetic macular edema (Protocol I). Ophthalmology. 2010;117(6):1064-1077.
   https://www.aaojournal.org/article/S0161-6420(10)00159-7/fulltext

3. Boyer DS, Yoon YH, Belfort R Jr, et al. Three-year, randomized, sham-controlled trial of dexamethasone intravitreal implant in DME. Ophthalmology. 2014;121(10):1904-1914.
   https://www.aaojournal.org/article/S0161-6420(14)00342-3/fulltext

4. American Academy of Ophthalmology IRIS Registry (Intelligent Research in Sight). Overview and data insights.
   https://www.aao.org/iris-registry

5. Stewart MW. Corticosteroid use for diabetic macular edema: old fad or new trend? Curr Diab Rep. 2012;12(4):364-375.
   https://link.springer.com/article/10.1007/s11892-012-0286-1