Eyesight

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

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 – branded Can-C.

He told in an interview recently that clinical studies have shown Can-C 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 subscapular cataracts.

“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

According to Dr. Babizhayev, the Can-C eye drop formula contains carboxymethylcellulose, which allows it to be sold as a lubricating eye drop. The product labeleling 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 Can-C, we can assist the lens to withstand the oxidative stress induced by phospholipid hydroperoxides in the surrounding medium in the aqueous humor,” he sai

The Can-C 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., (IVP) of Delaware, U.S.A.

The Can-C 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 Can-C 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.