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Eye drop may slow cataract development, researcher says
A study of 49 patients showed those treated with N-acetylcarnosine drops scored better in visual acuity and glare sensitivity measures.
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A lubricating eye drop that contains a specially formulated antioxidant compound may slow or even halt the progression of age-related cataracts, according to the lead scientist who developed the compound.
The eye drop contains the antioxidant N-acetylcarnosine and is being marketed by United Kingdom-based International Antiaging Systems Ltd. under the product name Can-C.
According to biophysicist Mark A. Babizhayev, PhD, N-acetylcarnosine is a naturally occurring prodrug of the antioxidant carnosine. Essentially, an acetyl valence is added to the carnosine molecule, which allows it to penetrate the cornea and enter the aqueous environment, he said. Within the aqueous, the molecule is then de-acetylated into pure carnosine.
Dr. Babizhayev is the lead researcher involved in trials of the compound. He also holds the international patents related to the N-acetylcarnosine eye drop formulation.
He told Ocular Surgery News in an interview that clinical studies have shown the product to improve vision in treated patients compared to placebo. He noted, however, that for patients to achieve the optimal benefit, they should have vision no worse than 0.3.
He said the studies mainly included eyes with cataracts that involved some membrane component, such as cortical and subcapsular cataracts.
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| Images of a human eye at baseline (A-B) and several months after treatment with eye drops containing N-acetylcarnosine (C-D). Images: Babizhayev MA | |||
“In these cataracts, we can predict a significant improvement. When we face brunescent, nuclear cataracts and the vision is depressed significantly, then the effect of improvement is less pronounced,” he said.
Dr. Babizhayev said he is currently working with several drug companies in the United States that are seeking U.S. Food and Drug Administration regulatory trials and subsequent approval to market it as a pharmaceutical.
N-acetylcarnosine
According to Dr. Babizhayev, the eye drop formula contains carboxymethylcellulose, which allows it to be sold as a lubricating eye drop. The product labeling states that N-acetylcarnosine is an antioxidant added to the drop.
He noted the molecule’s antioxidant activity depends on the intraocular absorption and subsequent breakdown of N-acetylcarnosine, which is aided by carboxymethylcellulose.
Dr. Babizhayev said the absorption and breakdown of N-acetylcarnosine can be hindered if other antioxidants, such as vitamin A or vitamin E, are added to the formulation, preventing the formation of pure carnosine. Thus, a proprietary formulation was developed to achieve the maximum intraocular effect, he said.
“N-acetylcarnosine itself is a weak antioxidant. The ideal use of this therapeutic modality is to stimulate the conversion of N-acetylcarnosine into carnosine intraocularly, in the aqueous humor,” he said.
After its conversion, the carnosine acts as a “universal antioxidant” both in the lipid phase of biological membranes and in the aqueous environment, Dr. Babizhayev said, protecting lipid membranes and water soluble molecules such as proteins, DNA and sugars.
“The idea is, if we can repair lipid membranes of the lens fiber cell membranes … we can reduce opacification of the lens due to the particular redox balance existing. Carnosine is acting as the de-linker in the lens because it scavenges the aldehyde products. Then the whole redox balance shifts to positive, and the lens can withstand the oxidative stress by its own means,” he said.
Dr. Babizhayev said the lens is equipped with non-enzymatic and enzymatic antioxidant systems that mediate the action of the universal antioxidant L-carnosine released from the N-acetylcarnosine topically applied to the eye in eye drops.
“The lens is not just an optical lens; it works as a metabolic system. If the redox balance is positive, it works in a good fashion. With our product, we can assist the lens to withstand the oxidative stress induced by phospholipid hydroperoxides in the surrounding medium in the aqueous humor,” he said.
Clinical study
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The eye drops have been evaluated in clinical trials by Dr. Babizhayev and colleagues at the Hemholtz Research Institute of Eye Disorders, Moscow. The trials were organized by Innovative Vision Products Inc., of Delaware, U.S.A.
The trials evaluated efficacy using stereocinematographic slit-lamp photography and a specially designed device called a halometer, a glare disability test that monitors small changes in lens opacity, he said. Results of the trials were published in Drugs in R&D, Peptides and Journal of Anti-Aging Medicine.
In the study, 49 patients (76 eyes) were randomly assigned to eye drops containing 1% N-acetylcarnosine or a placebo twice daily over 6 months or out to 2 years follow-up.
According to the study, control patients showed a gradual worsening of visual acuity and no significant difference in lens clarity at 5- to 6-month follow-up.
However, N-acetylcarnosine-treated eyes showed statistically significant differences in visual acuity, glare sensitivity and other characteristics of image analysis compared to eyes in the control group (P < .001).
An improvement in visual acuity of 7% to 100% was seen in 37 of 41 (90%) N-acetylcarnosine-treated eyes. A significant improvement of 27% to 100% in glare sensitivity at red and green targets was seen in 16 of 18 (89%) tested eyes, and during image grading a significant improvement in lens clarity was seen in 17 of 41 (41%) eyes, according to the study.
The authors noted that no significant differences in cumulative lens changes were seen between 6 months and 24 months follow-up in N-acetylcarnosine-treated eyes. However, the results at 24 months showed the effect of N-acetylcarnosine is sustainable over a long period, with 20 of 23 (87%) treated eyes showing a 12% to 67% improvement in visual acuity.
The results were significantly different from eyes treated in the control group, of which 17 of 19 (89%) eyes showed a 17% to 80% deterioration in visual acuity at 24 months follow-up (P < .001).
A note from the editor:
While no anti-cataractogenesis drops are available in the United States, several products are available worldwide. All use some form of antioxidant or free-radical scavenger. Much basic science supports the role of antioxidants such as glutathione in the maintenance of a clear lens. Nonetheless, quality prospective clinical trial data is lacking to date to support the use of these medications. For example, the National Eye Institute’s prospective clinical trial evaluating antioxidant vitamins (the Age Related Eye Disease Study), while supporting antioxidant use in select cases of age-related macular degeneration, showed no value of antioxidants in retarding the progress of cataract. It is important to follow research in this area, but no definitive support is currently available for such drops.
Richard L. Lindstrom, MD
OSN Global Medical Editor
For Your Information:
- Mark A. Babizhayev, PhD, is executive director of Innovative Vision Products Inc., which developed N-acetylcarnosine. He can be reached at Ivanovskaya 20, Suite 74, Moscow 127434, Russia; phone/fax: +7-095-977-2387; e-mail: markbabizhayev@yahoo.com. Dr. Babizhayev is the worldwide patent holder of the N-acetylcarnosine eye drops therapeutical modality.
References:
- International Antiaging Systems Ltd., marketer of the Can-C eyedrops containing N-acetylcarnosine, can be reached at Les Autelets, Sark GY9 0SF, England; +44-870-151-4144; fax: +44-870-151-4145; e-mail: ias@antiaging-systems.com.
- Babizhayev MA, Deyev AI, et al. Lipid peroxidation and cataracts: N-acetylcarnosine as a therapeutic tool to manage age-related cataracts in human and in canine eyes. Drugs R D. 2004;5(3):125-139.
- Babizhayev MA, Deyev AI, et al. Efficacy of N-acetylcarnosine in the treatment of cataracts. Drugs R D. 2002;3(2):87-103.
- Babizhayev MA, Yermakova VN. Imidazole-containing peptidomimetic NACA as a potent drug for the medical treatment of age-related cataract in humans. J Anti Aging Med. November 2000;3:43.
- Babizhayev MA, Deyev AI, et al. N-acetylcarnosine, a natural histidine-containing dipeptide, as a potent ophthalmic drug in treatment of human cataracts. Peptides. 2001;22(6):979-994.
- Michael Piechocki is an OSN Staff Writer who covers ophthalmology in Europe, Asia and the Pacific region. He also specializes in oculoplastic topics.