Drug repurposing involves identifying new therapeutic uses for existing medications. Also known as drug repositioning or reprofiling, this approach focuses on finding novel applications for compounds already approved or significantly investigated. This strategy leverages known drug properties to address different medical needs.
The Advantages of Drug Repurposing
Drug repurposing offers several benefits compared to traditional drug development. A primary advantage is reduced time to market. Since existing drugs have completed initial human safety testing, they can often bypass early-stage clinical trials, saving years in development.
This expedited process also leads to lower development costs. Traditional drug discovery is expensive, often costing billions and taking over a decade. Drug repurposing can reduce these costs significantly, sometimes by 50-60%, making it a more financially attractive option.
Another benefit is the known safety profile of repurposed drugs. These compounds have been extensively studied in humans, providing data on their pharmacology, dosage, and side effects. This pre-existing safety information lowers clinical trial risks and streamlines regulatory approval. The success rate for repurposed drugs is also higher than for novel drugs, with approximately 30% achieving approval compared to about 10% for new drug applications.
Methods of Identifying New Uses
Scientists employ various approaches to uncover new uses for existing drugs. Computational methods leverage big data, artificial intelligence, and bioinformatics to predict drug-disease relationships. These “in silico” techniques analyze biological, chemical, and clinical data to identify patterns and suggest new therapeutic indications.
Experimental approaches involve screening large libraries of existing compounds against different disease models. High-throughput screening allows researchers to rapidly test thousands of drugs for desired biological activity. This can involve cell-based assays or animal experiments to evaluate a drug’s efficacy.
Clinical observation and anecdotal evidence also play a role. Healthcare providers sometimes notice unexpected effects in patients treated with a drug for its original indication. These “off-label” uses provide initial clues for further investigation. Understanding a drug’s mechanism of action, or how it interacts with biological targets, can also suggest new therapeutic areas. If a drug affects a particular pathway or protein, researchers can explore other diseases involving the same pathway.
Impactful Examples of Repurposed Medicines
Many well-known medications have found new life through repurposing. Sildenafil, famously known as Viagra, was initially investigated by Pfizer as a treatment for angina, a type of chest pain, and high blood pressure. During clinical trials, researchers observed an unexpected side effect: improved erectile function, leading to its repurposing for erectile dysfunction. Sildenafil was later repurposed a second time in 2005 to treat pulmonary arterial hypertension, a condition involving high blood pressure in the lungs.
Thalidomide, a drug with a complex history, was originally marketed in the 1950s as a sedative and to treat morning sickness, but was later withdrawn due to severe birth defects. Despite its notorious past, thalidomide was successfully repurposed for treating multiple myeloma, a type of blood cancer, and certain complications of leprosy.
Aspirin, or acetylsalicylic acid, has been used as a pain reliever since 1899. In the 1980s, it was repurposed for cardiovascular disease prevention due to its ability to inhibit platelet aggregation. Low doses of aspirin are now commonly used to reduce the risk of heart attacks and strokes. Research also explores its potential in preventing certain cancers, such as colorectal cancer, owing to its anti-inflammatory effects.
Minoxidil, initially an oral medication for severe hypertension, was repurposed for hair loss treatment. The observation of hair growth as a side effect in patients taking minoxidil led to the development of a topical formulation for androgenetic alopecia. Metformin, a widely used drug for type 2 diabetes, is also being investigated for its potential anti-cancer properties, with research exploring its effects on various cancer types, including non-small cell lung cancer.