New pharmacologic approaches to treating diabetic retinopathy

The goal of treatment of diabetic retinopathy, limitations of laser photocoagulation, endpoints used in clinical studies of diabetic retinopathy treatments, and the mechanism of action, efficacy, and safety of several new and emerging therapies targeting the biochemical pathways that link chronic hyperglycemia with microvascular damage in patients with diabetic retinopathy are discussed.

Improving or preserving vision is the primary goal of treatment for diabetic retinopathy. Limitations of laser photocoagulation include a lack of efficacy in some cases, discomfort from the procedure, the need for repeated treatment, and a risk of retinal damage and scarring. Visual acuity, quality of life, and macular thickness are used as endpoints in clinical studies of diabetic retinopathy treatments. Microvascular damage in patients with chronic hyperglycemia is mediated by interrelated pathways involving aldose reductase, advanced glycation end products, protein kinase C (PKC), and vascular endothelial growth factor (VEGF). Oral aldose reductase inhibitors have been studied with some success only in patients with diabetic peripheral neuropathy. The oral PKC inhibitor midostaurin and oral selective PKC beta inhibitor ruboxistaurin appear promising for improving or maintaining visual acuity, with gastrointestinal complaints the most commonly reported adverse effects. Intra-vitreal injection of corticosteroids or VEGF inhibitors is associated with short-lived improvement in or maintenance of visual acuity, a need for repeated injection, and a risk of local adverse effects.

A variety of promising new therapies for diabetic retinopathy targeting the biochemical pathways that cause microvascular damage are under investigation. Additional clinical research is needed to determine the role of these new therapies in treating diabetic retinopathy.