On March 20, 2012, the U.S. Supreme Court decided Mayo Collaborative Services v. Prometheus Laboratories, Inc., No. 10-1150, holding that two patents that relied on a law of nature to assess the correct dosage of certain drugs did not claim subject matter that was eligible for patenting because laws of nature cannot be patented, and the steps added by the claims consisted only of well-understood, routine, conventional activity.
Prometheus Laboratories is the exclusive licensee of two patents concerning the use of thiopurine drugs to treat autoimmune diseases. The patents set forth processes for optimizing the therapeutic efficacy of a drug, based on natural correlations between metabolite levels produced by the drugs and efficacy. The claimed processes consist wholly of three steps: administering the drug, determining the level of metabolites produced by the drug, and assessing whether to adjust the dosage of the drug in response. Mayo Collaborative Services initially purchased diagnostic tests based on the Prometheus patents, but later announced plans to sell and market its own test. Prometheus sued Mayo for patent infringement. The district court found that the Mayo test infringed the Prometheus patent, but nevertheless granted summary judgment for Mayo on the ground that the processes claimed by the patent effectively claimed natural laws or phenomena that were not patent eligible. The Federal Circuit reversed, holding that the processes were patentable under the "machine or transformation test," and later reaffirmed that decision after the Supreme Court vacated the original decision remanded for reconsideration in light of its decision in Bilski v. Kappos, 130 S.Ct. 3218 (2010).
The Supreme Court unanimously reversed the Federal Circuit, holding that the Prometheus process is not patent eligible. Section 101 of the Patent Act extends patent protection to "any new and useful process." 35 U.S.C. § 101. But the Supreme Court has long held that this provision contains an implicit exception that precludes the patenting of laws of nature, natural phenomena, or abstract ideas. The Prometheus process, held the Court, was founded on a law of nature—namely, the natural correlation between concentrations of certain metabolites in the blood and the likelihood that a dosage of a certain drug will prove ineffective or cause harm.
The question of patent eligibility, therefore, was whether "the patent claims add enough to their statements of the correlations to allow the processes they describe to qualify as patent-eligible process that apply natural laws?" The Court held that they did not. Qualifying steps must contain "features that provide practical assurance that the process is more than a drafting effort designed to monopolize the law of nature itself." Here, the three steps claimed by the patents consisted solely of "well-understood, routine, conventional activity already engaged in by the scientific community." They added nothing of value to the law of nature itself, and hence did not make the process patent eligible.
The Court noted that the patents here raise the very concern that the Court has relied on in barring the patenting of natural laws or phenomena: that rewarding broad patents that preempt a law of nature will inhibit future innovation. Moreover, in this particular situation, awarding such a broad patent would place restrictions on doctors' decisions based on the underlying knowledge of the natural law or phenomenon and thus inhibit the development of more refined treatment recommendations that may combine the natural phenomenon observed here with future discoveries.
Justice Breyer delivered the decision for a unanimous Court.