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Mayo Collaborative Services v. Prometheus Laboratories

Supreme Court Strikes Down Medical Test Patent


The U.S. Supreme Court rejected a patent on a medical test that merely recognized naturally occurring phenomena. Ruling otherwise would have increased health care costs and limited incentives for real innovations in medical care.


Patents reward inventors by providing a fixed period of exclusivity during which they can be compensated for their research, innovation, and hard work by being the sole provider or licensor of the invention they have developed. However, under patent law not everything can be patented. While new tools for measurement or detection can be patented, laws of nature are not patentable. Science and engineering would grind to a halt if patents could be issued for “laws of nature” — for example, if merely observable occurrences could be patented, legal restrictions would prevent anyone from looking at the sun in order to figure out what time it is.

Mayo v. Prometheus presented a question of whether the discovery that certain drugs have specific correlations to medical conditions is patentable. In this case, the test involved measuring the level of a chemical in the body and is routinely used by doctors to test for the effects of thiopurine drugs for diseases such as leukemia, rheumatoid arthritis, and Crohn’s disease, and for organ transplants. If the patent was upheld, not only would these tests be more expensive, but medical testing and treatment could be delayed by perceived threats of patent violations when doctors simply use medical facts to diagnose and treat disease.

AARP’s brief, filed by attorneys with AARP Foundation Litigation, argued that it is outside of the letter and intent of patent law to allow patents for the scientific fact that there is a correlation between levels of a vitamin and levels of a chemical in the body. Patenting the linkage of a naturally occurring phenomenon would prevent doctors from merely thinking about medical facts necessary for sound medical treatment, and potentially even consumers could be held liable for patent infringement.

The Court agreed, writing unanimously that “If a law of nature is not patentable, then neither is a process reciting a law of nature, unless that process has additional features that provide practical assurance that the process is more than a drafting effort designed to monopolize the law of nature itself.” The Court reiterated its concern “that patent law not inhibit further discovery by improperly tying up the future use of laws of nature.”

What’s at Stake

As America’s population ages, the demand for health services (including frequent medical testing and screening) will increase. Upholding patent claims such as those in this case would significantly stifle competition, increase costs and, most important, impede progress in the medical diagnosis industry — not just in this situation (which in and of itself affects a vast number of people), but in cases of other medical diagnoses.

Case Status

Mayo Collaborative Services v. Prometheus Laboratories was decided by the U.S. Supreme Court.

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Find cases in which AFL has advocated in courts nationwide for the rights of older persons, and filed AARP’s amicus curiae (“friend of the court”) briefs that help courts decide precedent-setting cases. The cases within the drop-down categories below are in alphabetical order for ease of searching.

Strengthening Law and Policy through
Legal Advocacy

Our legal advocacy initiatives  - conducted by AARP Foundation Litigation (AFL) - reflect nearly 20 years of work in federal and state courts across the country. Through our efforts, we support the Foundation’s four impact areas: Tackling Senior Hunger, Paving the Way to Stable Income, assuring the adequacy and availability of Safe and Afffordable Housing and Reconnecting People to Families and Communities, and ensure that those 50 and older have a voice in the laws and policies that affect their daily lives.