Breakthrough on the Horizon for Topical Diabetic Retinopathy Treatment

Diabetic retinopathy (DR) is currently the leading cause of blindness in working-age populations and among the most serious complications of chronic diabetes.

An article in the March 14, 2014, issue of Endocrine indicates European researchers are in the midst of a multicenter, phase II-III, randomized control clinical trial to assess the efficiency of topically-administered brimonidine and somatostatin to treat DR. The clinical trial, EUROCONDOR-278040, first launched in February 2013, and final results are expected in 2016.

The article described the study’s rationale in detail. The human retina abundantly produces somatostatin (SST), mainly in the retinal pigment epithelium. SST reacts with retinal SST receptors to exert neuromodulation, angiostatic, and anti-permeability functions. Since studies have shown that the diabetic retina down-regulates SST, SST replacement may be a viable target for DR treatment.

Researchers have avoided topical eye medications to prevent or arrest DR due to assumptions that topical medications do not effectively reach the eye’s posterior chamber. However, mounting evidence suggests that topical SST or SST analogs could play a key role in preventing the main pathogenic mechanisms involved in DR. Topical administration of SST has effectively prevented retinal neuro-deregulation in streptozotocin-induced diabetic rats. These successful results coupled with a desire to avoid aggressive intravitreous injections of SST in early stages prompted a team of researchers to initiate the EUROCONDOR study design.

Previous clinical trials using SST analogs administered intramuscularly to arrest DR progression were not successful. Researchers speculated that SST analogs administered intramuscularly may penetrate the blood-brain barrier inadequately and attain poor tissue distribution in the retina. In addition, the SST analogs may have a lower affinity for SST receptors in the retina than local SST produced in the retina.

Pharmacological treatment with topical SST may be a rational approach to treating DR. The results of the EUROCONDOR clinical trial will be a step forward in establishing SST effectiveness and safety in the fight against this horrific complication of diabetes.