Phase III clinical trial of Ruboxistaurin (RBX) at a concentration of 32 milligrams/day was found to inhibit Protein kinase C (PKC) - beta inhibitor, which was found to cause vision loss in patients with diabetes.
The study was conducted in 252 patients with type 1 or type 2 diabetes by the Research team of Joslin Diabetes Centre across United States, Canada, Denmark, Netherlands and United Kingdom. The study was named as PKS-DRS, (Protein Kinase C - Diabetic Retinopathy Study), was done to evaluate the oral administration of RBX and placebo over a period of 3-4 years at a concentration of 8, 16 or 32 mg/day.
Incidence of eye complications is high in Diabetic patients, with common complications of diabetes causing diabetic retinopathy and diabetic macular edema. Diabetic retinopathy is characterised by damage to small blood vessels in the retina and causes severe vision loss. Diabetic macular edema is characterised by leaky blood vessels with swelling in the retina.
Protein kinase C is required for the normal production of energy in the body, but â-form of PKC has found to cause diabetic complications of the eye. â- PKC is the major signaling pathway which is stimulated by high blood glucose levels. In animal studies it was found that the abnormal activation of â-PKC decreases the blood flow to the retina.
The research team has found oral administration of 32 milligrams/day of Ruboxistaurin, blocks the activity of â-Protein kinase C. Moreover, RBX was found to be specific in binding only to the â-form of PKC. Though, RBX does not prevent the progression of diabetic retinopathy, it reduces the vision loss which is caused by macular edema. RBX in the study group did not produce any side-effects.