Review of Existing Drugs for the Treatment of Alzheimer's Disease

A research team has identified three already approved drugs that could potentially be used to treat or prevent Alzheimer's disease. Instead of developing new medications from scratch, the experts analyzed drugs currently used for other conditions to determine their possible protective effects on the brain.

Overview of Dementia and the Drug Discovery Approach

Dementia is one of the leading causes of death in the UK, affecting around one million people. One in three people born today may develop this condition during their lifetime, yet there is still no effective treatment. Developing new drugs typically takes 10–15 years and requires significant financial investment, with no guarantee of success. Repurposing already approved and widely used medications is seen as a faster, safer, and more accessible way to find new treatments for Alzheimer's disease.

Selection of Promising Drugs

An international group of 21 dementia specialists from universities, medical institutions, the pharmaceutical industry, and individuals with lived experience of dementia evaluated 80 existing drugs. Their goal was to identify the most promising candidates for the treatment or prevention of Alzheimer's disease, which accounts for more than half of all dementia cases.

After a multi-stage selection process, three priority candidates were chosen for further research. Each was selected based on its impact on biological processes associated with Alzheimer's, positive results in cell and animal studies, and safety for older adults.

The Three Priority Drugs

1. Shingles Vaccine (Zostavax)
   Research suggests a possible link between the shingles virus and dementia. Changes in the immune system are known to play a role in the development of Alzheimer's, and this vaccine may help prevent some of these negative changes.

2. Sildenafil (Viagra)
   Studies indicate that this drug may protect nerve cells and reduce the accumulation of tau protein, which abnormally builds up in Alzheimer's disease. In mouse experiments, sildenafil also improved cognitive function, possibly by increasing blood flow to the brain.

3. Riluzole
   Used to treat amyotrophic lateral sclerosis (ALS), riluzole has been shown to improve cognitive function and lower tau protein levels in animal studies.

Key Features and Next Steps

Among the three drugs, the shingles vaccine stands out because it requires no more than two doses and has a long-established safety record. Previous studies have shown that people who received this vaccine were about 16% less likely to develop dementia.

A large clinical trial of the shingles vaccine is planned in the UK, using the online PROTECT registry, where volunteers annually provide health and lifestyle data and participate in brain health studies.

Additional Candidates

Five other drugs were included in the shortlist, but were not prioritized. These include:

• Fingolimod (used for multiple sclerosis)
• Vortioxetine (for depression)
• Microlithium (for depression)
• Dasatinib (for leukemia)
• Cytisine (used in anesthesia)

The Need for Further Research

Large-scale clinical trials are necessary to confirm the effectiveness and safety of the selected drugs. Only after these studies are completed can conclusions be drawn about the appropriateness of using these treatments for Alzheimer's disease prevention or therapy.