About 32% of Small-Molecule Drugs Later Gain a Second Approved Use
Aspirin for hearts, a gout drug for hearts, and an asthma drug for food allergies show how common second acts are.
The Works in Progress Newsletter · Are miracle drugs hiding in plain sight?About 32% of small-molecule drugs approved by the U.S. Food and Drug Administration between 1997 and 2020 later won approval to treat another condition. Small-molecule drugs are small chemicals, not hormones, peptides, vaccines, or antibodies, and they tend to travel widely and reach many parts of the body.
That second act is often surprising. Aspirin had been in use for more than a century before researchers confirmed during the 1980s that it also helped treat cardiovascular disease. Colchicine, an ancient medicine for gout, a painful joint condition, was later found to help heart disease. And omalizumab, first sold for asthma, turned out to help treat food allergies.
The share could grow if the clock runs for another couple of decades, since drugs from that batch will have more time to gain new uses. The formal count also understates reuse, because American doctors can legally prescribe a drug for another condition without waiting for regulators to approve the new use.
Questions people ask
What exactly is a small molecule drug?
A small molecule drug is a simple chemical compound, usually taken as a pill, that is tiny enough to move through the gut and blood and reach many tissues. That is different from larger medicines like vaccines, insulin and other hormones, and antibodies made in living cells. Because they travel widely, small molecules are more likely to affect more than one part of the body.
If a drug already exists, why does it need a second approval?
A doctor can prescribe an approved drug off label, meaning for a condition not listed on its official label, if the doctor judges it may help. That happens often once early evidence appears. Formal FDA approval for the second use still matters, because it usually requires stronger trial evidence and lets the maker advertise the new use.
Why would a drug made for one disease work for another?
Many drugs touch targets found in more than one organ, and different diseases can share the same biological pathway. An asthma drug that calms an overactive immune response, for example, can also calm a food allergy. Sometimes the link is indirect, since treating one problem like obesity also lowers the risk of heart disease and related conditions.