Description

Drug repurposing also known as drug repositioning refers to the process of identifying new therapeutic uses for existing drugs. This approach has gained significant attention in the pharmaceutical and biomedical fields due to its potential to reduce the time, cost and risk associated with drug development. Unlike traditional drug discovery which can take over a decade and cost billions of dollars repurposing leverages the known safety profiles and pharmacokinetics of approved or investigational drugs to expedite the development process. Drug repurposing has led to discoveries including the use of sildenafil originally developed for angina for erectile dysfunction and pulmonary hypertension, and thalidomide infamous for its teratogenic effects for leprosy and multiple myeloma. This article the mechanisms methodologies applications, challenges and future directions of drug repurposing. Many diseases share underlying molecular pathways. Drugs targeting one pathway in a specific disease may be effective in another condition involving the same pathway. Anti-inflammatory drugs originally developed for autoimmune diseases are being explored for cancer treatment due to their role in modulating the tumor microenvironment.

Tumor

Drugs often interact with multiple molecular targets leading to off-target effects. These effects when carefully studied, can be harnessed for therapeutic purposes. Aspirin initially developed as an analgesic and anti-inflammatory is now widely used for its antiplatelet effects in cardiovascular disease prevention. Diseases with limited or no effective treatment options drive the search for repurposed drugs to address urgent therapeutic gaps. Chloroquine an antimalarial drug was repurposed during the pandemic due to its antiviral properties. Libraries of approved drugs are screened against new disease targets to identify potential therapeutic candidates. Drugs are tested in cellular or animal models to observe their effects on disease phenotypes without prior knowledge of the molecular target. Computational tools analyses large datasets including drug databases omics data and clinical records to identify potential drug-disease associations. Virtual simulations predict how well a drug binds to a new target guiding experimental validation. Examines drug interactions within biological networks to uncover new therapeutic applications. Adverse effects observed in clinical trials or post-marketing surveillance can provide clues for repurposing. The antihypertensive drug monoxide was repurposed for hair growth after patients reported unexpected hair regrowth. Retrospective analyses of patient data can reveal associations between drug use and reduced incidence of certain conditions. Statins primarily used for cholesterol management have shown potential in reducing cancer risk in some observational studies. Cancer is a prime area for drug repurposing due to its complex and heterogeneous nature.

Mutations

Orphan diseases which affect a small percentage of the population benefit significantly from drug repurposing due to the high cost and limited commercial interest in new drug development. Initially developed for specific mutations in cystic fibrosis is being tested for other rare genetic conditions. Drugs for cardiovascular conditions often have overlapping mechanisms with other metabolic disorders leading to repurposing opportunities. Safety and pharmacokinetic profiles are already established allowing faster transition to clinical trials. Drugs with known mechanisms of action and established efficacy are less likely to fail in new applications. Repurposed drugs can address urgent healthcare needs such as pandemics or emerging diseases. Leverages existing investments in drug discovery and development. Many repurposed drugs are offpatent leading to limited financial incentives for pharmaceutical companies. Developing new formulations or combinations to create market exclusivity. Regulatory frameworks for repurposed drugs vary across regions requiring extensive documentation and clinical validation. Navigating these processes can delay drug approval. Balancing the need for rapid deployment against rigorous testing can pose ethical dilemmas particularly during public health demergencies. Advances in genomics and proteomics enable the identification of patient subgroups most likely to benefit from repurposed drugs. Synergistic effects of repurposed drugs in combination with existing therapies to enhance efficacy.