The cost of healthcare in general is a debilitating, pre-existing condition for Americans. But the high prices of prescription drugs usually stand out as a pain point. While there are many insidious reasons why Americans pay more—often far more—for their medicines than people in peer countries, exploitation of the US patent system is an obvious one.

A study published Monday in JAMA highlights just how much patent exploitation has grown since 1990. In that time, researchers found the number of patents on small-molecule drugs have more than tripled, going from an average of 2.1 patents per drug approved in 1990 to 6.9 for those approved in 2019.

Most of the growth was in “nonprimary” patents—patents that generally aren’t related to a drug’s active ingredient, but are instead for things like minor tweaks to a drug’s non-active ingredients, updates to the way the drug is used, or the design of specialty delivery devices, such as auto-injectors. Together, those extra patents on an individual drug can create what’s called a “patent thicket,” which delays the release of affordable generics on the market, keeping drug prices higher for longer without actual clinical advancements.

The study—led by S. Sean Tu, an expert in drug and patent law at the University of Alabama—found that the increase in patents per drug extended the time in which a drug was patented from an average of two years in 1990 to an average of 6.1 years in 2019.

“Because patent protection typically determines how long brand-name firms can charge monopoly prices, the rapid growth of nonprimary patents may contribute to limited price competition that benefits patients and the health care system by helping avoid unnecessary spending,” Tu and colleagues write.

Patent overgrowth

For the study, Tu and colleagues used publicly available data to look at small-molecule drugs approved by the Food and Drug Administration and the patents filed on those drugs. (Other types of approved drugs, like biologics, are not systematically listed by the FDA in a publicly available database.) The researchers categorized the types of patents associated with each drug and how they affected the term in which the drug remained under patent. The researchers focused on drugs granted FDA approval between 1990 to 2019, giving a five-year follow-up period for patents. Still, this likely underestimates the current sizes of patent thickets, as patent activity is now extending up to nine years after FDA approval, the authors write.