Diabetic retinopathy is the leading cause of newly diagnosed blindness in the working age (20-74) population in the United States1 and diabetic macular edema (DME) is the leading cause of vision loss in diabetic retinopathy. DME is the result of the breakdown of the retinal capillary endothelium in patients with diabetes mellitus (Type I and II).~A key factor in the development of DME is the permeability of the blood-retinal barrier. The breakdown of the endothelial tight junctions of the capillary walls in the retinal vasculature leads to increased permeation of salts, proteins, and water from the capillary luminal side of the barrier and the accumulation of fluid in the extracellular space. Multiple agents appear to contribute to the disruption of the blood-retina barrier,including vasoactive agents, prostaglandin and vascular endothelial growth factor (VEGF). VEGF is a peptide that promotes neovascularization and increases vascular permeability. If the resulting fluid is more than the amount that can be removed through the active pump mechanism (retinal pigmented epithelium), fluids continue to accumulate and edema develops. When thickening evolves or threatens the center of the fovea there is a high risk of visual loss.~Cand5 is a synthetic double stranded RNA (dsRNA) oligonucleotide. The molecule is a duplex formed by the hybridization of two partially complementary single strand RNAs in which the 3' end are capped with 2 deoxyribose (dT) units. Hybridization occurs across 19 ribose base pairs to yield the Cand5 molecule. Cand5 has a molecular weight of 13,345 grams/mole. Cand5 selectively silences the mRNA encoding for VEGF.~A comparison will be made between the three (3) treatment arms with regard to safety, efficacy, and duration of effect to determine a safe and efficacious dose of Cand5 appropriate for evaluation in future pivotal trials.
The purpose of this study is to evaluate the pharmacokinetics, safety and preliminary efficacy of 3 doses of Cand5. Cand5 is a small interfering RNA molecule that selectively silences the mRNA encoding for VEGF. The target population are patients with diabetic macular edema.