Drug repositioning

Drug repositioning (also known as drug repurposing, drug reprofiling or therapeutic switching) is the process of identifying new uses for approved or investigational drugs that are outside the scope of the original medical indication.

Overview

Drug repositioning is a strategy for identifying new uses for drugs that are already on the market, bypassing the time and cost associated with traditional drug discovery. This approach can be particularly beneficial in the treatment of rare or orphan diseases, where the potential market may not be large enough to justify the cost of developing a new drug from scratch.

Process

The process of drug repositioning can be divided into two main approaches: serendipitous discovery and systematic screening.

Serendipitous discovery is when a new therapeutic use for a drug is discovered by chance. This often occurs during clinical trials for a different indication, or during post-marketing surveillance when unexpected benefits are reported by patients or healthcare professionals.

Systematic screening involves testing a library of approved drugs against a range of diseases in a high-throughput manner. This can be done in vitro using cell-based assays, or in vivo using animal models of disease.

Examples

One of the most famous examples of drug repositioning is the case of sildenafil (Viagra). Originally developed by Pfizer for the treatment of angina and hypertension, it was found during clinical trials to have a notable side effect of inducing erections, and was subsequently repositioned for the treatment of erectile dysfunction.

Another example is thalidomide, which was originally marketed in the 1950s as a sedative and antiemetic for morning sickness, but was withdrawn from the market due to its teratogenic effects. It was later repositioned for the treatment of multiple myeloma and leprosy after its anti-inflammatory and immunomodulatory effects were discovered.

Challenges and opportunities

While drug repositioning offers a potentially faster and cheaper route to drug development, it is not without its challenges. These include regulatory issues, intellectual property concerns, and the need for further clinical trials to validate the new indication.

However, the opportunities presented by drug repositioning are significant. By leveraging existing data and knowledge, drug repositioning can reduce the risk, cost and time associated with bringing a new drug to market. Furthermore, it can provide new treatment options for patients, particularly those with rare or orphan diseases for which there are currently limited therapies available.

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