Existing drugs could prevent vision loss, macular degeneration

Bright light can cause damage to retinal tissue and cause vision loss or blindness. Scientists from Case Western Reserve University have found that a combination of FDA-approved drugs could protect against retinal damage and ward off some vision-impairing conditions, including macular degeneration.

The team genetically modified mice to be more susceptible to retinal damage and exposed them to 30 minutes of bright light, according to a statement. Some of the mice’s photoreceptor cells died, leaving behind a thinner retina. The surviving photoreceptors were damaged, mimicking human retinal degeneration.

The researchers, led by Krzysztof Palczewski, selected drugs known to act on G protein-coupled receptors--which ferry signals in and out of cells--that activate specific proteins linked to retinopathy, or retinal disease that causes vision loss. They then pre-treated mice with 16 different drugs in a bid to shield them from retinal damage. It worked: The pre-treated mice escaped photoreceptor damage caused by bright light.

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With a shortlist of four drugs, the team tested low-dose combinations to find the most effective regimen to ward off bright light-caused photoreceptor damage. While metoprolol, used to treat several cardiovascular conditions, worked best individually, the researchers ultimately found that a combo of metoprolol, bromocriptine and doxazosin or tamsulosin all at “sub-therapeutic” doses, did better than any drug alone. Bromocriptine treats a range of conditions brought on by pituitary problems, as well as Type 2 diabetes, while the latter two drugs are both urinary retention meds used in the treatment of prostate cancer.

“This project is ready for clinical tests assessing effectiveness in age-related macular degeneration and Stargardt disease,” Palczewski said in the statement. And the systems pharmacology method--which seeks to understand how drugs work on different systems of the body--could be applied to conditions beyond retinopathy: “All chronic illnesses and aging diseases should be tested using similar approaches to those developed in our study,” Palczewski said.