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Unsuccessful Clinical Trials in Retina: Lessons Learned
1From the Duquesne University College of Osteopathic Medicine (DUQCOM) (J.T.), Pittsburgh, Pennsylvania, USA.
Purpose:
To analyze patterns of nonsuccess in phase 2 and 3 interventional retinal clinical trials conducted in the United States between 2015 and 2025.
Design:
Perspective based on retrospective analysis of unsuccessful clinical trials.
Methods:
Unsuccessful trials that were terminated, withdrawn, or completed without meeting primary endpoints were evaluated across indications, trial phases, intervention classes, and mechanisms of action to identify recurring design, feasibility, and operational challenges.
Results:
High attrition rates were observed across diabetic macular edema, diabetic retinopathy, neovascular age-related macular degeneration, and geographic atrophy. Phase 2 trials were more frequently discontinued following interim analyses, whereas phase 3 trials more often failed to meet primary efficacy endpoints. Later-phase studies were associated with increased sample size, geographic dispersion, follow-up duration, and assessment burden. Differences in endpoint selection, comparator choice, and population heterogeneity may contribute to attenuation of treatment effects. Operational and sponsor-level factors, including strategic and financial considerations, were also associated with trial discontinuation.
Conclusions:
Translating early-stage findings into successful late-phase outcomes remains challenging in retinal drug development. Improved alignment of biological rationale, endpoint selection, and operational feasibility may enhance trial success.
Insights
High attrition rates plague late-stage retinal clinical trials. Improving trial design, endpoint selection, and operational factors is crucial for successful drug development in ophthalmology.
Area of Science:
- Ophthalmology
- Clinical Trial Design
- Retinal Diseases
Background:
- Retinal drug development faces significant challenges in translating early-stage successes to late-phase trials.
- High attrition rates are a persistent issue in interventional retinal clinical trials.
Purpose of the Study:
- To analyze patterns of non-success in US-based phase 2 and 3 interventional retinal clinical trials from 2015-2025.
- Identify recurring design, feasibility, and operational challenges contributing to trial failures.
Main Methods:
- Retrospective analysis of unsuccessful clinical trials (terminated, withdrawn, or failed primary endpoints).
- Evaluation across indications (diabetic macular edema, retinopathy, AMD, geographic atrophy), trial phases, intervention classes, and mechanisms of action.
Main Results:
- High attrition observed in diabetic macular edema, diabetic retinopathy, neovascular AMD, and geographic atrophy.
- Phase 2 trials often discontinued post-interim analysis; Phase 3 trials frequently missed primary efficacy endpoints.
- Later-phase trials showed increased complexity (sample size, duration, burden); endpoint selection and operational factors contributed to failures.
Conclusions:
- Translating early retinal research findings into successful late-stage outcomes remains difficult.
- Enhancing alignment between biological rationale, endpoint selection, and operational feasibility is key to improving trial success rates in ophthalmology.
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