Viagra May Reduce Risk of Alzheimer’s Disease

NIA-funded researchers have found that people who took the drug sildenafil, sold under the brand names Viagra and Revatio, were less likely to develop Alzheimer’s disease (AD). Sildenafil also enhanced growth and reduced Alzheimer’s biomarkers in cultured human neurons. The findings appeared in Nature Aging.

“This is one of many efforts we are supporting to find existing drugs or available safe compounds for other conditions that would be good candidates for Alzheimer’s disease clinical trials,” said NIA program director Dr. Jean Yuan. Repurposing existing drugs could reduce the time and costs of bringing AD therapies to patients.

Researchers began by identifying genes associated with AD pathology. Then they constructed a network of molecular interactions connecting these genes. They also assembled networks of drugs and their molecular targets for more than 1,600 FDA-approved drugs. They then calculated the relationships between each drug’s targets and the AD network components.

The team identified 66 drugs with the closest relationships to AD-associated genes. Many are already being tested in ongoing AD clinical trials, proving the soundness of the approach. After considering other factors, sildenafil ended up being the top candidate. 

Next, the team analyzed insurance claims data from more than 7 million Americans. They found that the people (mostly men) who took sildenafil were 69 percent less likely to develop AD over 6 years than those who did not take the drug. This association between sildenafil and AD held after adjusting for sex, age and other diseases and conditions.

To understand how sildenafil might affect AD, the researchers grew neurons from stem cells derived from AD patients. Exposing the cells to sildenafil led to increased growth of neurites, which connect neurons to each other. Sildenafil also reduced tau phosphorylation, an early biomarker of AD.

While these results show an association between sildenafil use and reduced AD risk, the researchers emphasized they haven’t shown that sildenafil prevents or reverses AD. There may be other factors responsible for the association.—Brian Doctrow, NIH Research Matters