Researchers discover tamsulosin, metoprolol, and bromocriptine effectively slow the progression of retinal failure when taken together.
Drug repurposing – using existing medications for new “off-label” therapeutic purposes – is gaining traction in medical research. This practice uses established safety profiles and known pharmacological effects of drugs already on the market to determine off-label uses or, in other words, identify conditions that the drugs can treat that were not part its originally intended use. By doing this, a multitude of conditions may be treated without having to push new formulas through a trial-to-market pipeline, which is often much more time-consuming.
A new study from an international team of researchers published in Nature Communications took a look at how drug repurposing, by way of a combination therapy, can be used to treat inherited retinal degenerations (IRDs). Specifically, the team showed how a blend of tamsulosin, metoprolol, and bromocriptine effectively slows the progression of retinal failure in the pre-clinical stage.
The recent study focused on IRDs, a group of genetic disorders that cause progressive loss of retina function, which is a thin layer of tissue that the back of the eye, usually lead to vision impairment, and sometimes, blindness. To date, most IRDs lack effective treatments, meaning individuals often can do little about these disorders.
The team wrote, “Most inherited retinal degenerations (IRDs) are currently inaccessible therapeutically, comprising an unmet medical need for a substantial population worldwide. IRDs affect approximately 1 in 2000 people globally, and often lead to blindness in childhood2. IRDs, including distinct forms of retinitis pigmentosa (RP), are associated with hundreds of distinct genetic mutations. Management of all those mutations by targeted therapies, mainly gene therapy, is likely to remain impractical and prohibitively expensive for the foreseeable future.”
The researchers explored the benefits of taking three drugs together – metoprolol, which is a medication used for high blood pressure, to slow heart rate, and for heart failure, tamsulosin, often prescribed to treat benign prostatic hyperplasia, and bromocriptine, for Parkinson’s disease. When used together, these drugs significantly slowed retina disease progression in four different animal models of IRDs.
Dr. Henri Leinonen, the study’s first author and an Adjunct Professor of Neuropharmacology at the University of Eastern Finland, explained, “In drug repurposing, the original use of the drugs is less important than their molecular effects. In retinal degenerations, secondary messengers like cyclic adenosine monophosphate and calcium are overactive, worsening the disease. Metoprolol, tamsulosin, and bromocriptine each suppress these messengers through distinct mechanisms.”
The researchers hypothesized that the effect of these drugs when taken together would ward off the disease, and their results confirmed this across multiple IRD models. However, Dr. Leinonen said that the efficacy and safety of this off-label drug combination in humans with retinal degeneration remain to be validated through controlled clinical trials. The next steps will involve more focused and intensive clinical trials to validate these initial findings in humans and determine the practical applications of this promising approach. Safety profiles will also need to be evaluated extensively to determine the long-term implications of taking these three medications together.
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