The Supreme Court Reduces Patent Protection for Medical Diagnosis and Analysis

Life Sciences Alert



On March 20, 2012, the U.S. Supreme Court released its long-awaited decision in the case of Mayo Collaborative Services v. Prometheus Laboratories, Inc. slip. op., Case No. 10-1150 (March 20, 2012). This decision resolves a patent infringement case in which Prometheus Laboratories, Inc. (“Prometheus”) alleged that Mayo Collaborative Services (“Mayo”) infringed patents for a method of correcting an overdose or an under-dose of a thiopurine drug. The U.S. Supreme Court unanimously held that Prometheus’ method is not patent-eligible.

Thiopurine drugs are used to treat autoimmune diseases, but their safety and efficacy depend in large part upon each individual patient’s ability to process and metabolize the drugs. Individual patients vary widely in terms of their reaction to a given dosage of thiopurine drugs. Consequently, it is very difficult to determine a safe and effective dose of thiopurine drugs for any given patient. It has long been known that the variability of an individual’s response to the drugs is partially due to the fact that different patients process them at different rates. When a thiopurine drug is processed by a patient’s body, a chemical product known as a “metabolite” is created from the drug. It was also known that the concentrations of two particular metabolites are each related to the proper dose of thiopurine drugs. However, this relationship was not understood with any precision, and consequently it could not be practically used to hone dosages for the individual.

Scientists working at the Hopital-Sainte-Justine in Montreal discovered the precise limits for these metabolites in the blood within which thiopurine drugs are both effective and safe. With this knowledge, the Hopital-Sainte-Justine patented a “method of optimizing therapeutic efficacy” for treating disease with thiopurine drugs. In simplified form, the patented method involves:

  1. administering a thiopurine drug;
  2. determining the level of the certain metabolites in the patient’s blood; and
  3. either increasing or decreasing the patient’s dosage of the thiopurine drug if the level of such metabolites is outside of the critical range.

Prometheus is the exclusive licensee of the patents in the United States. Mayo initially sub-licensed the test from Prometheus, but Mayo started using the test without a license, and Prometheus sued for patent infringement.

The Litigation
The case was brought in federal district court; the district court decided that the patents were invalid, because they claimed a “natural phenomenon or law of nature” which is prohibited under the U.S. Supreme Court decision Diamond v. Diehr, 450 U.S. 175, 185 (1981). On appeal, the U.S. Court of Appeals for the Federal Circuit reversed the district court’s decision. The Federal Circuit held that the patents did not cover a natural phenomenon or a law of nature because the patents require tangible steps: administering medication to a patient (which is then chemically transformed to a metabolite) and determining the concentration of the metabolite in the patient. Consequently the Federal Circuit found the patents to be valid.

The Supreme Court’s Decision
The U.S. Supreme Court reversed the Federal Circuit, and in doing so significantly limited the types of methods that are eligible to be patented. The Supreme Court decided that the patented method is a “natural phenomenon or law of nature,” and thus cannot be patented. The tangible steps recognized by the Federal Circuit were deemed by the Supreme Court to be too insignificant to render the method eligible for a patent. The Court found that every step in the method was already well known, except the step of acknowledging whether the patient’s metabolite levels are within the desired range. Because the correlation of metabolites with thiopurine drug activity alone would be considered a natural phenomenon or law of nature, the Court held that merely adding well-known steps to the understanding of this correlation was not sufficient. The Court summarized its position 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.”

The Impact on Diagnostic and Analytical Patents
This decision significantly reduces the ability of an inventor to patent a method of diagnosis or analysis in the United States. Furthermore, this decision is not necessarily limited to medical inventions, but any invention that includes a logical step, or application of a natural correlation. However, it is important to note that this decision does not affect the patentability of new devices or new chemicals that are useful in diagnosis or analysis; only the methods themselves are affected.

Any owner or licensee of the rights to such an invention (including but not limited to inventions that are under development, and inventions subject to pending and issued patent applications) should immediately analyze whether such inventions will be impacted by this decision. If a non-public invention (including an invention that is the subject of an unpublished patent application) would now be unpatentable under the Prometheus decision, serious consideration should be given to protecting the invention as a trade secret, even if it means abandoning pending patent applications in the United States or other countries.

This decision likely invalidates thousands of issued patents. Owners and licensees of patents that cover analytical or diagnostic methods should immediately evaluate such patents to determine their validity under Prometheus. If one or more claims are invalid, it may be possible to modify them to restore their validity by means of a reissue proceeding or the newly-enacted supplemental examination process.

Given the courts’ contracting notions of what may be patented, and their progressively higher standards for upholding patents once issued, trade secret protection is an increasingly attractive option for protecting investments in new inventions. Going forward, it is advisable to take measures under applicable state trade secret laws to ensure that this avenue of protection remains available.