The double effect of sildenafil
Viagra was suggested to be used to treat Alzheimer's disease
Anastasia Kuznetsova-Fantoni, Elizaveta Ivtushok, N+1
American researchers using a network analysis of 1,600 FDA-approved drugs found that Viagra can be effective in the treatment of Alzheimer's disease. In addition, scientists analyzed databases of insurance companies in the United States and found that patients who were prescribed Viagra had a six-year risk of developing Alzheimer's disease 69 percent lower than other people. The study is published in Nature Aging (Fang et al., Endophenotype-based in silico network medicine discovery combined with insurance record data mining identifies sildenafil as a candidate drug for Alzheimer's disease).
Drugs for the treatment of Alzheimer's disease appear infrequently. Recently, the FDA approved a new drug for Alzheimer's disease, which was the first in 18 years. The process of selecting new drugs is quite long: first, the candidate needs to undergo preclinical tests, and then prove their safety and effectiveness in humans. The task is simplified if you immediately look for candidate drugs among approved drugs - then you do not have to prove that they are safe for humans. At the same time, it often turns out that drugs that treat some diseases are effective for the treatment of others. For example, metformin has recently been associated with a reduced risk of Alzheimer's disease.
A similar approach was applied by American doctors under the leadership of Feixiong Cheng from the Cleveland Clinic: they were looking for drugs for the treatment of Alzheimer's disease among already approved drugs. At first, the researchers used computational methods to break down the molecular characteristics of Alzheimer's disease into 13 phenotypes based on differences in gene expression, gene polymorphisms, and protein expression. Next, a network analysis was applied between information on 351444 protein-protein interactions, divided into 13 endophenotypes, and 1600 FDA-approved drugs. Each drug from the selected list is already used to treat diseases from 12 groups (cardiovascular diseases, diseases of the nervous system, respiratory diseases, and so on).
The network analysis took into account the endophenotypes of each drug — that is, which biomarkers are affected by its components. By the distance between the endophenotypes associated with Alzheimer's disease and the biomarkers affected by drugs, scientists have calculated the most suitable drug — the one that affects most of the biomarkers associated with Alzheimer's disease: it turned out to be sildenafil, better known as Viagra.
The researchers then analyzed databases of U.S. insurance companies and found that patients who were prescribed Viagra had a six-year risk of developing Alzheimer's disease 69 percent lower than other people. The Cox regression, which was used for statistical analysis, was also adjusted for the age and ethnicity of the participants. However, most of the patients in the analysis were men, which affected the heterogeneity of the sample.
The authors warn that the found connection may be accidental and in the future clinical studies are needed, which will include both women and men, as well as a placebo group.
Viagra has been used in clinical practice for a long time, so it most likely will not cause side effects in patients. The same cannot be said about the recently approved drug for Alzheimer's disease: in patients who took it, foci of hemorrhages and brain edema were found on MRI.
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