Certiorari to the United States Court of Appeals for the Federal Circuit
Date of judgment: March 20, 2012
The patents in the present matter related to the use of thiopurine drugs in the treatment of autoimmune diseases, such as Crohn’s disease and ulcerative colitis. When a patient ingest a thiopurine compound, his body metabolize the drug, causing metabolites to form in his bloodstream. Because the way in which people metabolize thiopurine compounds varies, the same dose of a thiopurine drug affects different people differently, and it has been difficult for doctors to determine whether for a particular patient a given dose is too high, risking harmful side effects, or too low, and so likely ineffective.
At the time the discoveries embodied in the patents were made, scientists already understood that the levels in a patient’s blood of certain metabolites, including, in particular, 6-thioguanine and its nucleotides and 6-methyl-mercaptopurine, were correlated with the likelihood that a particular dosage of a thiopurine drug could cause harm or prove ineffective. But those in the field did not know the precise correlations between metabolite levels and likely harm or ineffectiveness. The patent claims at issue set forth processes embodying researchers’ findings that identified these correlations with some precision.
Respondent, Prometheus Laboratories, Inc, was the sole and exclusive licensee of the patents. It sold diagnostic tests that embodied the processes the patents describe. For some time petitioners, Mayo Clinic Rochester and Mayo Collaborative Services (Mayo), bought and used those tests. But in 2004 Mayo announced that it intended to begin using and selling its own test—a test using somewhat higher metabolite levels to determine toxicity. Prometheus then brought the present action claiming patent infringement. The District Court found that Mayo’s test infringed the patent. In interpreting the claim, the court accepted Prometheus’ view that the toxicity-risk level numbers in Mayo’s test and the claim were too similar to render the tests significantly different. The number Mayo used was too close to the number the claim used to matter given appropriate margins of error. The District Court also accepted Prometheus’ view that a doctor using Mayo’s test could violate the patent even if he did not actually alter his treatment decision in the light of the test.
But the District Court granted summary judgment in Mayo’s favor. The court reasoned that the patents effectively claimed natural laws or natural phenomena—namely the correlations between thiopurine metabolite levels and the toxicity and efficacy of thiopurine drug dosages—and so were not patentable. On appeal, the Federal Circuit reversed. It pointed out that in addition to these natural correlations, the claimed processes specify the steps of (1) “administering a thiopurine drug” to a patient and (2) “determining the resulting metabolite level.” These steps, it explained, involve the transformation of the human body or of blood taken from the body. Thus, the patents satisfied the Circuit’s “machine or transformation test,” which the court thought sufficient to “confine the patent monopoly within rather definite bounds,” thereby bringing the claims into compliance with §101.
Mayo filed a petition for certiorari. The Supreme Court granted the petition, vacated the judgment, and remanded the case for reconsideration in light of Bilski. On remand the Federal Circuit reaffirmed its earlier conclusion. It thought that the “machine-or-transformation test,” understood merely as an important and useful clue, nonetheless led to the clear and compelling conclusion that the claims do not encompass laws of nature or preempt natural correlations. Mayo again filed a petition for certiorari.
The Supreme Court observed that Prometheus’ patents set forth laws of nature—namely, relationships between concentrations of certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove ineffective or cause harm. While it take a human action (the administration of a thiopurine drug) to trigger a manifestation of this relation in a particular person, the relation itself exist in principle apart from any human action. The relation is a consequence of the ways in which thiopurine compounds are metabolized by the body—entirely natural processes. And so a patent that simply describes that relation sets forth a natural law. The question before the Court was whether the claims do significantly more than simply describe these natural relations. To put the matter more precisely, do the patent claims add enough to their statements of the correlations to allow the processes they describe to qualify as patent-eligible processes that apply natural laws? The Supreme Court answered it in negative and held that the patent claims effectively claimed underlying laws of nature themselves and thus the claims were held invalid.