Health Law Case Brief: Mayo Collaborative Services v. Prometheus Laboratories, Inc.

By: Kristyn Bunce DeFilipp

On March 20, 2012, the Supreme Court unanimously held that patent claims that help doctors who use thiopurine drugs to treat patients with autoimmune diseases determine whether a given dosage is too low or too high were unpatentable pursuant to 35 U.S.C. § 101, because the claims set forth laws of nature rather than applications of those laws.

Respondent Prometheus is the sole licensee of two patents, U.S. Patent Nos. 6, 355,623 (‘623 patent) and 6,680,302 (‘302 patent).  The ‘623 and ‘302 patents address the use of thiopurine drugs, a group of antimetabolites, in the treatment of autoimmune diseases.  Thiopurine drugs cause metabolites to form in the patient’s bloodstream andbecause different people metabolize thiopurine at different rates, the same dose of a thiopurine drug affects different people differently.Medical research established that the levels of certain metabolites in a patient’s blood could indicate whether a thiopurine dose was too high (and possibly dangerous) or too low (and likely ineffective).  The ‘623 and ’302 patents embody certain research findings that specify the correlation between the particular metabolites and the preferred dosage with some precision.  Prometheus sells diagnostic tests that employ the processes described in the ‘623 and ‘302 patents.

The petitioners, Mayo Clinic Rochester and Mayo Collaborative Services (collectively Mayo), formerly bought and used Prometheus’ diagnostic tests.  In 2004, Mayo indicated that it had developed its own test, which it planned to use and sell.  Prometheus sued Mayo for patent infringement in the U.S. District Court for the Southern District of California.  The district court found that Mayo’s test infringed one claim of the ‘623 patent, but granted summary judgment in Mayo’s favor, finding that Prometheus’ patents claim natural laws or natural phenomena that are not patentable.

Prometheus appealed this decision to the Federal Circuit.  The Federal Circuit applied the “machine or transformation test” and found that two steps in the patent claims “transformed” the human body or the blood taken from it:  the patents specify steps of “administering” the thiopurine drug to the patient, and “determining” the metabolite level. [1]

Mayo filed a petition for certiorari to the Supreme Court, and it granted certiorari, vacated, and remanded the Federal Circuit’s decision in 2010, indicating that it should be reviewed in light of the Court’s decision in Bilski v. Kappos.[2]   The Federal Circuit considered the case again and came to the same conclusion:  the patents were valid.  Mayo filed a second petition for certiorari, which the Supreme Court granted.

Breyer wrote for a unanimous Court, first examining the patent claims for “additional features” beyond a law of nature, “that provide practical assurance that the process is more than a drafting effort designed to monopolize the law of nature itself.”[3]  The Court addressed the steps of the process that the Federal Circuit had held were enough to transform the claims into patentable material:  the “administering” step, the “determining” step, and the “wherein” step.[4]  The Court found that these steps simply indicate that the patent is directed to doctors who treat patients using thiopurine drugs, and that those doctors should use the natural law described in the patent when they are treating those patients and by measuring metabolites in their blood.  “The upshot is that the three steps simply tell doctors to gather data from which they may draw an inference in light of the correlations.”[5]  The Court found that these steps were not enough to transform the natural correlations into patentable applications.

In finding the claims unpatentable, the Court considered its most relevant precedent on patentable subject matter, Diehr[6] and Flook[7].  In Diehr, the process for molding raw, uncured rubber into cured, molded products was found to be patentable because, although it centered on a basic mathematical equation (which, like a natural corollary, is not patentable), it integrated that equation with additional steps into a process.  The patent in Flook described an improved system for updating alarm limits in the catalytic conversion of hydrocarbons, but it did not limit the claim to a particular application and so was found unpatentable.  The Court found that methods in the ‘623 and ‘302 patents were weaker than the claims in Diehr and no stronger than those in Flook.  Like the invention in Flook, the patents simply provided instructions in applying a law of nature that were already “well-understood, routine, conventional activity, previously engaged by those in the field.”[8]

The Court went on to describe other cases supporting its view that “simply appending conventional steps, specified at a high level of generality, to laws of nature, natural phenomena, and abstract ideas cannot make those laws, phenomena, and ideas patentable.”[9] This review included an English case that instructed users that hot air promotes ignition better than cold air, but did so by describing the implementation of the principle in an inventive way.[10]  Thus, the English court held the invention patentable.  The Court also considered Bilski, which described a mathematical formula that allowed users to hedge risks in investing (unpatentable), and Benson,[11] which rejected the patentability of implementing a mathematical principle on a physical machine in order to convert binary-coded decimal numbers into pure binary numbers.

The Court’s holding in Prometheus works to avoid an unwarranted monopoly on a law of nature, which could impede medical research by disallowing the development of more refined treatment methods that utilize the same law.  The Court quoted from the amicus brief of several medical associations, which argued that “if claims to exclusive rights over the body’s natural responses to illness and medical treatment are permitted to stand, the result will be a vast thicket of exclusive rights over the use of critical scientific data that must remain widely available if physicians are to provide sound medical care.”[12]  Even so, the Court recognized the arguments advanced by Prometheus and the amici that agreed with it, that the medical diagnostics field is driven by investments that are motivated by the exclusivity guaranteed by patent protection.

The Court’s decision does not shut the door on patents for medical diagnostics; rather, it sets another benchmark in the jurisprudence of patentable subject matter which inventors of diagnostic tools that make use of natural laws must aim to overcome.

Kristyn Bunce DeFilipp serves as an Associate in Foley Hoag’s Litigation and Labor and Employment departments.  Kristyn represents clients involved in complex litigation matters involving commercial contract disputes, intellectual property and other business disputes.  Her practice includes a focus on labor and employment issues in litigation.

Kristyn advises and represents corporations in all aspects of labor and employment law. She has experience in labor arbitrations involving unions, including disputes involving just cause termination and organizing campaigns.  Kristyn also defends clients against discrimination, harassment and wage and hour lawsuits. She represents companies in federal and state courts, before administrative agencies including the Massachusetts Commission Against Discrimination, and before the American Arbitration Association.  In addition, Kristyn drafts employment handbooks and policies in order to ensure that employers comply with both state and federal employment law statutes, and provides advice to clients on these topics.

Kristyn is also active in the firm’s pro bono program. Her pro bono practice is varied, and includes assistance with obtaining restraining orders for protection against abuse for victims of domestic violence; assistance to parents and students on special education matters; and pursuit of Chapter 7 and Chapter 13 bankruptcy relief for individual debtors.

Prior to joining Foley Hoag, Kristyn interned at Neighborhood Legal Services in Lynn, Massachusetts, where she assisted low-income clients with housing-related legal issues.


[1] See 581 F.3d 1336, 1345 (Fed. Cir. 2009)

[2] Bilski v. Kappos, 561 U.S. __ (2010)

[3] Prometheus, 566 U.S. __  (2012) (slip op. at 8-9).

[4] Id. at 9.

[5] Id. at 10-11.

[6] Diamond v. Diehr, 450 U.S. 175 (1981).

[7] Parker v. Flook, 437 U.S. 584 (1978).

[8] 566 U.S. __ (slip op. at 13).

[9]Id. at 14.

[10] Neilson v. Harford, Webster’s Patent Cases 295 (1841).

[11] Gottschalk v. Benson, 409 U.S. 63, 67 (1972).

[12] 566 U.S. at ___ (slip op. at 23) (quoting Brief for American College of Medical Genetics et. al. as Amici Curiae 7.)

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