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M. J. Byrnes, S. Saigal, D. Waters-Honcu, R. T. Tzekov; Current Pipeline for Treatment of Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):83.
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Laser photocoagulation (PRP and focal; a surgical procedure) has been the standard of care for PDR and DME for over 25 years. In this presentation, we review current drug pipelines for diabetic retinopathy and assess the likelihood of new therapies emerging. We further review the primary endpoints typically used and reasons why several trials have recently failed in Phase 3.
A comprehensive list of ongoing or recently concluded clinical trials for diabetic retinopathy (DR) was prepared by consulting clinicaltrials.gov, published literature, and the internet. We then subdivided the data based on indication (NPDR, PDR, or DME), stage, and drug class. Finally, we review endpoints and available results for recently completed Phase 3 trials.
We identified 45 clinical trials for DR testing 25 therapeutic agents and involving > 22,000 patients worldwide. The distribution was weighted towards later-phase trials: 8 Phase 1 & 1/2, 13 Phase 2 & 2/3, and 21 Phase 3 & 4. The trials included 25 for DME and 12 for PDR. Twenty of the 25 therapies were for DME and PDR; only 4 were new chemical entities. The most common drug classes were corticosteroids (n=6) and anti-angiogenics (n=8). Phase 3 trials for 5 therapies have recently been completed. Of these, Avastin has shown promise as a treatment for both PDR and DME. Triamcinolone, ruboxistaurin, octreotide, and candesartan each showed efficacy but failed primary endpoints in Phase 3. Frequent primary endpoints were visual acuity (n=18) and DR progression (n=5).
Most of the therapies currently in trials for diabetic retinopathy are repurposed agents. Drug development for DR is difficult, because: a) PRP is ~90% effective under optimal conditions; b) visual acuity is often unaffected until advanced DR; c) efficacy measures may not be scalable from Phase 2 to Phase 3. Currently, no agents have surpassed PRP as the standard of care for PDR. However, PRP is associated with side effects that could be avoided by an effective pharmacologic agent or ameliorated by an adjunctive agent.
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