Date Posted: 16 April 2010
A multi-centre Phase I/II clinical trial has presented initial results for a new topical drug focused on the treatment of diabetic eye disease. The clinical research, reported by Dr. Peter Campochiaro and colleagues at the Wilmer Eye Institute, John Hopkins, showed that mecamylamine drops applied over a course of 1 to 16 weeks were well tolerated and showed no drug related safety problems.
The experimental drug, previously employed as an anti-depressant and smoking cessation aid, comprised a new formulation of 0.1 to 1.0% mecamylamine, developed for topical ocular use. Mecamylamine is a non-specific nicotinic acetylcholine (nACh) receptor antagonist previously approved as an oral anti-hypertensive agent in the 1950s. it has been well documented that nicotine stimulates choroidal neovascularisation in the eye, potentially increasing progression to neovascular AMD. Stimulation of nicotinic acetylcholine (nACh) receptors on vascular endothelial cells promotes angiogenesis and vascular permeability in animal models. Acting as an antagonist of nACh receptors, mecamylamine was tested to determine if such application could reduce abnormal retinal vascular permeability in patients with diabetic macular edema (DME).
In the study, participants administered mecamylamine eye drops themselves twice a day for 16 weeks allowing researchers to subsequently measure both the safety and efficacy of the drug. Eight of twenty-one trial participants showed significant improvements both in the thickness of the retina and in overall vision however, four patients showed substantial worsening while three patients initially showed improvement but experienced a "substantial worsening in BCVA between week 8 and 12". The authors of the study concluded that the somewhat divergent effects might be explained by the existence of one or more nACh receptor subtypes which could have opposing effects on endothelial permeability. While further work will be required there may be promise in the development of more specific nACh antagonists. Commenting on the study, Dr. Barbara Araneo, Director, Diabetic Complications Research at the Juvenile Diabetes Research Foundation stated that " the safety and early signals of treatment effect arising from this study may create a strong interest in the development of multiple treatment options that are affordable and can be self-administered, helping to ease the burden of healthcare delivery and compliance".
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