In Mayo Collaborative Services v. Prometheus Laboratories, Inc., 132 S. Ct. 1289 (2012) (No. 10-1150), the Supreme Court held a patent that claimed a method of measuring metabolites in the blood stream was invalid because it covered an unpatentable law of nature.  This decision reversed the holding of the Federal Circuit below.  

The patent claims at issue in this case are directed to a method of measuring metabolites in the human body to help determine the most effective dosage of thiopurine drugs used to treat autoimmune diseases.  Each patient’s body metabolizes the drugs differently, so doctors found it difficult to determine whether the dosage was too high or too low for each individual patient.  The patentee, Prometheus, identified a correlation between metabolite levels in the blood and the most effective dosage of the drugs in each patient, and developed a kit to determine if a patient’s metabolite levels were within the range Prometheus identified and claimed in the patent at issue.  Mayo developed its own diagnostic test and Prometheus sued Mayo for infringing its patent.

The District Court in the case granted summary judgment in Mayo’s favor, holding the patents invalid because they simply claim the correlations between thiopurine metabolite levels and the toxicity and efficacy of thiopurine drug dosages, which are natural phenomena.  The Federal Circuit reversed because it held the patent claims require the steps of administering a drug to a patient and determining the resultant metabolite level, which involve transformation of the drug in the human body or of blood taken from the body.  Therefore, the Federal Circuit held the patents satisfied the “machine or transformation test,” which it used as one way to determine that the patent claims were valid under § 101.

The Supreme Court held that the patents were directed to an unpatentable law of nature, the relationship between concentrations of certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove ineffective or cause harm.  The Court focused on the fact that it found the claims simply described a natural relationship, without including any patent-eligible processes that apply the relationship in a patentable way.  The Court pointed out that fundamental advancements in science that recognize important natural relationships, such as E=mc2, are unpatentable because it would stifle the ability of every other scientist to use that relationship in any way.  The Court analyzed each step in the patent claims and pointed out that even though there were some steps that were not laws of nature, those steps were already well-known in the art and therefore could not transform the claim into patent-eligible subject matter.  The step in the patent claim that was alleged to be new was the ideal range of metabolite levels in the blood stream.  

Notably, the Supreme Court did not cite Federal Circuit precedent in its opinion, but instead focused on its own precedent in Diehr and Flook.  The patent in Diehr was held valid by the Supreme Court because, even though it contained the use of a basic mathematical equation which was unpatentable, the equation was integrated into an overall process that was an inventive application of the formula.  The patent in Flook, on the other hand, was held invalid because it described a method for adjusting alarm limits which included only monitoring alarm limits using a mathematical algorithm to calculate new alarm limits and adjusting the system to the new alarm limits.  Since the use of the mathematical formula was not limited to a specific application, it was an invalid attempt to claim a simple algorithm.  The Court held the patents at issue in Mayo were in between Diehr and Flook, but more closely analogous to those in Flook, so the patents were invalid.  

The Court concluded that the patent claims at issue effectively claimed the underlying laws of nature themselves and the claims were consequently invalid under 35 U.S.C. § 101.