“More Than a Drafting Effort”: SCOTUS Strikes Down Prometheus Labs Patents

On March 20, the Supreme Court handed down their unanimous decision in the case of Mayo Collaborative Services v. Prometheus Laboratories, Inc. The Court struck down Prometheus’s patents stating that, regardless of the language in the claims, they were effectively patents on a law of nature which is not allowed. The Court added that any process which recites a law of nature must have other features and limitations that “provide practical assurance that the process is more than a drafting effort designed to monopolize the law of nature itself.”

The Prometheus patents covered the concept of adjusting the dosage of thiopurine drugs based on the level of metabolites in a patient’s blood. The patents on the thiopurine drugs involved have long since expired and the patents in question claim no specific method for measuring the metabolite level in a patient. The now invalidated claims had two steps. The first step was simply the administration of the drug. The second step was the measurement of the metabolite in the patient after the administration. The remainder of the claim describes the correlation. If the metabolite concentration is higher than a certain value, this “indicate[s] a need” to reduce the next dose and vice versa.

The Mayo Clinic used the thiopurine metabolites test developed by Prometheus until 2004 when it developed its own test. Prometheus sued Mayo in 2004, alleging that the patents covered more than just the particular test that Prometheus had developed. Prometheus argued that the patents covered the entire process in the claims without any restriction to a particular method of administration or measurement. In effect, this prevented anyone else from making use of the correlation between certain metabolite levels and drug dosages however the patents were allowed as applications of this correlation.

The district court held that patents were invalid under §101 because they claimed scientific correlations which were natural phenomena that resulted from natural body processes. However, the Federal Circuit overturned this ruling and upheld the validity of the patents. The Federal Circuit relied on the machine or transformation test in coming to its decision. Understanding that the machine or transformation test is only a “useful  and important clue, an investigative tool,” the Federal Circuit held that the steps in the claims comprised a method of treatment which was a proper application of a scientific principle. In addition, the Federal Circuit noted that the method of treatment claimed in the patents satisfied the transformation prong of the machine-or-transformation test. Prometheus Laboratories, Inc. v. Mayo Collaborative Services, 628 F.3d 1347, 1355-57 (Fed. Cir. 2010).

The Supreme Court started its analysis by noting that the relationship between the concentration of metabolite in a patient’s blood and the efficacy of another dosage of the thiopurine drug is a law of nature that is not patentable. The relationship itself is simply a consequence of how the metabolite interacts with one’s body in a way that is separate from any human action. Thus, to be patentable, the claims have to contain additional features that conclusively show that the process applies the law of nature.

Identifying three additional features in the Prometheus patents, the Court found them all to be insufficient to deem the process an application of a law of nature. The first feature, the administration step, was dismissed as only identifying the people interested in the correlation. Specifically, the people interested are doctors using thiopurine drugs and this group existed before these patents existed. The measuring step does not make this claim patentable because the methods of measuring metabolite levels are well known in the art. Telling doctors to engage in routine, well known activity does not make this process patentable. Lastly, the explanation of the correlation adds little to the actual application of the process and just describes the law of nature. At most, it suggests that doctors should consider the test results when deciding the next dosage of the drug.

Because the features in the Prometheus claims were simply drafting efforts rather than substantive additions, the Supreme Court struck down the patents. However, the Court did not shed much light on what exactly constitutes an additional feature that would demonstrate an application of a law of nature. Finding the three additional features in the Prometheus claims to be insufficient gives some guidance, but no other specific explanation was provided.


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