The repurposing of drugs has been going on for a long time. Repurposing is the term used for using a drug for a different condition than what it was originally intended. Drug companies are pleased when they can find another use for an approved medication, the reasons are 1.) the drug has already been tested in humans 2.) the adverse reactions are well known 3.) the manufacturing process has been worked out 4.) and the dosing has been established. This saves the drug company hundreds of millions of dollars and can add an additional drug to treat a particular condition.
Here are some drugs that have been repurposed. One of the oldest of repurposed drugs is aspirin. It was brought to market in 1899 by Bayer Pharmaceutical Co. as a pain reliever (analgesic). In the 1980s it was starting to be used at low doses to prevent cardiovascular events because it was found to prevent platelet aggregation (clotting) and it is still used widely for this effect. However, aspirin is being repurposed again in oncology. It has been found that taking a daily dose of aspirin for at least 5 years can prevent many cancers, and in particular colorectal cancer.
Thalidomide is another interesting drug that has been repurposed. It was originally developed to treat nausea in pregnant women, but was banned in 1962 because it caused birth defects. However, it was shown that thalidomide had a dramatic effect in reducing an autoimmune complication of leprosy. In 1998 the Celgene Co. brought thalidomide back as an orphan drug to treat the rare disease, though with severe measures to prevent exposure to pregnant women. Much like aspirin thalidomide is being repurposed again in the field on oncology. It has shown efficacy against tumors leading to a place as a first-line treatment for multiple myeloma.
The famous drug sildenafil (Viagra) is an example of a repurposing of a drug before it reached the market. Sildenafil was being studied by Pfizer in 1985 as a potential antihypertensive medication. During the trials it was noticed that it had a noticeable effect in erectile dysfunction (ED). Pfizer changed the indication for sildenafil to ED and in 1998 brought the drug to market with an excess of 2 billion dollars in annual sales. Because of the antihypertensive effect of sildenafil, it is being repurposed again for use in pulmonary
hypertension, which is a potentially fatal increase of blood pressure between the heart and the lungs.
In 1819 dimethyl fumarate was synthesized and was used as a mold inhibitor to protect leather. It was brought to market in 1994 in Germany to treat psoriasis under the brand name of Fumaderm. Biogen repurposed this drug again to treat multiple sclerosis (MS) in 2013 as the drug Tecfidera.
A main focus of this approach is on Alzheimer’s Disease (AD). There have not been many drugs brought to market in almost 20 years to treat this disease. There are many clinical trials using the repurposing approach to find drugs to treat AD. Some of the drugs being looked at for AD are methylene blue, levetiracetam, cannabinoids, lithium, and insulins, among others.
Repurposing or repositioning of drugs will always be a fruitful method of drug discovery and we hope it continues.
Prosper and be in health.
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