The Supreme Court Further Defines the Scope of Patentable Subject Matter

March 30, 2012

Following its decision in Bilski1, on March 20, 2012, a unanimous (9-0) Supreme Court handed down its decision in Mayo v. Prometheus2-the Court’s second opinion on patentable subject matter in less than two years.  The Court in Mayo held that the claimed method for optimizing therapeutic efficiency for the treatment of an immune-mediated gastrointestinal disorder is not eligible for patent protection.

Prometheus is the sole and exclusive licensee of U.S. Patent Nos. 6,355,623 and 6,680,302, which claim methods for determining the optimal dosage of thiopurine drugs used to treat immune-mediated gastrointestinal disorders, and marketed a PROMETHEUS Thiopurine Metabolites test that used the technology covered by the patents-in-suit. 

Procedural History

Mayo initially purchased and used Prometheus’s test, but later announced that it intended to use and sell its own test.  Prometheus thereafter sued Mayo in the U.S. district court in California.  The district court granted Mayo’s motion for summary judgment of invalidity under 35 U.S.C. §101, finding that the claimed methods do not recite patent-eligible subject matter. 

Prometheus appealed, and the Federal Circuit reversed and “upheld the asserted claims’ validity under … the machine-or-transformation test.”3  Mayo then took its appeal to the Supreme Court.  The Court granted Mayo’s petition for certiorari, vacated the judgment, and remanded the case for consideration in light of Bilski.  On remand, the Federal Circuit reaffirmed its earlier decision.4  Mayo again filed a petition for certiorari, which was granted. 

At the Federal Circuit, Mayo had argued that the asserted claims are nearly identical to the claims in LabCorp v. Metabolite5 and are thus unpatentable laws of nature.  In LabCorp, the Supreme Court initially granted a writ of certiorari, and later dismissed it as improvidently granted.  Justice Breyer, with whom Justices Stevens and Souter joined, filed a dissenting opinion, stating that a correlation between homocysteine and vitamin deficiency is an unpatentable natural phenomenon.6  The Federal Circuit concluded, however, that the dissent is not controlling law and the claims at issue are different than those presented in LabCorp.

The Court’s Decision in Mayo

In the Mayo decision, authored by Justice Breyer, the Supreme Court first established that “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” are laws of nature7.  The Court then turned to the question of whether “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.”8  As in Bilski, the analysis of the Court “rests upon an examination of the particular claims … in light of the Court’s precedents.”9  The Court reiterated that “[i]f 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.”10  Using that standard, the Court concluded that the asserted claims do not recite patent-eligible processes. 

The Supreme Court used claim 1 of U.S. 6,355,623 as a representative claim.  Claim 1 reads:

  1. A method of optimizing therapeutic efficacy for treatment of an immune-mediated gastrointestinal disorder, comprising:
    (a) administering a drug providing 6-thioguanine to a subject having said immune-mediated gastrointestinal disorder; and
    (b) determining the level of 6-thioguanine in said subject having said immune-mediated gastrointestinal disorder,
    wherein the level of 6-thioguanine less than about 230 pmol per 8x108 red blood cells indicates a need to increase the amount of said drug subsequently administered to said subject and
    wherein the level of 6-thioguanine greater than about 400 pmol per 8x108 red blood cells indicates a need to decrease the amount of said drug subsequently administered to said subject.

The Court concluded that the administering step, the determining step, and the wherein clauses were not “sufficient to transform the nature of the claim.”11  Specifically, the Court reasoned that doctors-the audience of the administering step-used the thiopurine drugs to treat patients long before anyone asserted these claims; the wherein clauses only tell the doctors about the laws-the correlations between the metabolite levels and likely harm or ineffectiveness; the methods of determining metabolite levels were well known in the art; and the combination of these three steps added nothing patentable to laws of nature.

The Supreme Court conducted a further analysis by comparing this case with two of its precedents-Diehr12 and Flook13.  The Court stated that claim 1 “presents a case for patentability that is weaker than the (patent-eligible) claim in Diehr and no stronger than the (unpatentable) claim in Flook.”14  The steps and wherein clauses of claim 1 “add nothing specific to the laws of nature other than what is well-understood, routine, conventional activity, previously engaged in by those in the field.”15  The Supreme Court repeatedly described the steps recited in the asserted claims as “conventional.”


The Mayo decision reiterates that patent claims directed to laws of nature are not patentable absent the inclusion of patent-eligible subject matter.  The Mayo decision will likely have important consequences for biotechnology and pharmaceutical patent applications, particularly where claims are drafted to encompass a natural process, a correlation, or laws of nature.  As in Bilski, the Court again declined to define what constitutes a patentable process.  Instead, the Court invited patent applicants to look to “the guideposts in Benson, Flook, and Diehr.”16  In addition, while “recognize[ing] that, in evaluating the significance of additional steps, the §101 patent-eligibility inquiry and, say, the §102 novelty inquiry might sometimes overlap,” the Court stated that a §101 inquiry cannot be substituted by an inquiry under §§102, 103, and 112.

1Bilski v. Kappos, 130 S. Ct. 3218, 561 US __, 177 L. Ed. 2d 792 (2010).
2Mayo v. Prometheus, 566 U.S. ______ (2012).
3Prometheus v. Mayo, 581 F.3d 1336, 1352 (Fed. Cir. 2009).
4Prometheus v. Mayo, 628 F.3d 1347 (Fed. Cir. 2010).
5LabCorp v. Metabolite, 548 U.S. 124 (2006).
6LabCorp v. Metabolite, 548 U.S. 124, 138 (2006).
7Mayo v. Prometheus, 566 U.S. ______ (2012).  Slip Opinion at 8.
8Mayo v. Prometheus, 566 U.S. ______ (2012).  Slip Opinion at 8, emphasis in original.
9Mayo v. Prometheus, 566 U.S. ______ (2012).  Slip Opinion at 3.
10Mayo v. Prometheus, 566 U.S. ______ (2012).  Slip Opinion at 8-9.
11Mayo v. Prometheus, 566 U.S. ______ (2012).  Slip Opinion at 9.
12Diamond v. Diehr, 450 U.S. 175 (1981).
13Parker v. Flook, 437 U.S. 584 (1978).
14Mayo v. Prometheus, 566 U.S. ______ (2012).  Slip Opinion at 13.
16Bilski v. Kappos, 130 S. Ct. 3218, 3231 (2010).
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