Pharma Patent 'Thickets' Tripled Duration of Drug Exclusivity Since 1990, JAMA Study Finds

A study examining decades of U.S. drug approvals indicates that pharmaceutical manufacturers have sharply increased their reliance on secondary patents to extend commercial monopolies on brand-name medications. Published in JAMA and reported by Ars Technica (https://arstechnica.com/health/2026/09/to-keep-drug-prices-high-pharma-has-been-piling-up-the-patents/), the research outlines how drugmakers surround treatments with layers of auxiliary intellectual property, prolonging exclusivity periods without adding corresponding therapeutic advancements.

The investigation evaluated Food and Drug Administration approvals for small-molecule drugs between 1990 and 2019. Over that period, the average number of patents associated with each approved drug more than tripled, rising from 2.1 patents per medication in 1990 to 6.9 in 2019. Across the total sample of 1,981 approved small-molecule drugs, researchers identified 10,940 patent filings.

The surge in patent volume was driven almost entirely by "nonprimary" patents rather than discoveries tied to active ingredients. While primary patents changed little across the study window, nonprimary filings—which include minor modifications to inactive ingredients, alternative methods of use, and delivery mechanisms such as auto-injectors—comprised 84 percent of all patents identified across the approved drugs.

This accumulation of secondary intellectual property, known as a patent thicket, lengthened the duration of market protection. Led by S. Sean Tu, a professor of drug and patent law at the University of Alabama, the authors found that additional patents extended the average time a drug remained under patent protection from 2.0 years in 1990 to 6.1 years in 2019.

The lengthening exclusivity periods parallel broader increases in prescription spending. Citing a Peterson-KFF analysis, the report notes that inflation-adjusted per capita spending on prescription drugs in the United States grew from $291 in 1990 to $1,084 in 2019. A separate Commonwealth Fund analysis published earlier this year found U.S. per capita prescription drug spending was nearly double the average of peer high-income countries.

To compile the dataset, Tu's team tracked FDA public records for small-molecule drugs using a standardized five-year follow-up window after approval. Biologics were excluded because the FDA does not systematically catalog them in a public database. The authors noted that their findings likely underestimate current patent thicket sizes, as recent patenting activity frequently extends up to nine years post-approval. Although the study did not measure generic launch delays directly, the authors noted that industry arguments claiming add-on patents do not delay generics rely primarily on pre-2010 drug cohorts, which predated the recent surge in secondary patent filings.

To address patent proliferation, the authors recommended policy interventions including heightened review scrutiny at the U.S. Patent and Trademark Office, legislative limits on minor add-on patents, and judicial authority to require financial disgorgement from companies found to have abused the patent system.