July 2010 Clinical Laboratory News: Are Diagnostic Method Claims Patentable?

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July 2010: Volume 36, Number 7

Are Diagnostic Method Claims Patentable?
New Rulings Raise Old Questions

By Laurie A. Axford, Esq

U.S. patent laws are designed to prevent overreaching monopolies and to allow technological advancements, rather than stifling them. Therefore, to exclude as many competitors as possible from manufacturing or selling a similar invention, as well as turning their investment into a profit, companies try to write patent claims that give them broad patent protection. But when it comes to biological substances and processes, the question is: "Is it patentable?" The extent of the exclusions to patentable subject matter is not clear cut in the law. However, two recent court cases involving diagnostic methods have helped to further define these exclusions, and may provide some insights into where the line should be drawn.

Biomedical companies, like other high-tech firms, rely on the patentability of their inventions and the short monopolies that patents provide to justify the high costs of research and development. In order to be patentable, however, inventions must be useful, new, and non-obvious. Diagnostic methods are generally considered patentable processes, but their ultimate patentability depends on other factors that are less well defined in patent law.

One of the fundamental principles of U.S. patent law is that only certain subject matter is patentable (1). Recently, two court decisions related to the patentability of diagnostic claims has again opened debate on one of the most controversial principles in patent law today—whether things that exist in nature are patentable subject matter. This controversy centers on the contribution of an inventor, or the “hand of man,” and where the line should be drawn on patent claims for biological materials.

Take for example the discovery of a new species. Even though the species is “new,” the species itself is not patentable because it already exists in nature. However, genetic material is patentable under limited circumstances, even though it exists in nature. In this instance, the patent claims are limited to a form of the genetic material that involves human intervention, such as an isolated or cloned form.

When a company creates a new diagnostic assay, it attempts to protect its invention by filing for a patent. Most diagnostic patent claims state in the simplest sense, “A method of diagnosing disease X by measuring the amount of analyte Y in a patient’s sample, and comparing it to normal value Z, wherein if Y is greater than Z, the patient probably has disease X.” Usually, in order to establish patentability, the threshold question is whether the inventor is the first person to recognize the relationship between disease X and analyte Y. However, as the two recent cases below demonstrate, even if the invention is “new,” it must also constitute patentable subject matter.

Case One

Prometheus Laboratories, Inc., a specialty pharmaceutical company, holds exclusive license to a method patent for a treatment involving administration of the drug thiopurine, used to treat inflammatory bowel diseases, and detection of metabolites of the drug to determine if the dosage should be altered (2). Although this is a treatment patent, the step of detecting the metabolites is, in fact, a diagnostic method. In a lawsuit, Prometheus claimed that Mayo Clinic was infringing on its patent claims by conducting its own test for the metabolite (3). Mayo defended its use of the test on the basis that the patent claim was invalid, because it covered the result of what happened in the body naturally: formation of the drug's metabolites. Mayo's defense further asserted that determining the level of metabolites was nothing more than “data gathering.”

The district court sided with Prometheus, ruling that Mayo's test infringed one of the patent claims. When Mayo appealed this decision to the federal court, the judge held that the “determination step” was sufficient by itself to establish patentable subject matter, because the metabolites could not be detected upon inspection. In other words, it took the “hand of man” to combine them with a reagent to make them detectable. In the fall of 2009, Mayo petitioned the U.S. Supreme Court to hear its case challenging the patentability of Prometheus’ assay and is waiting to hear if the court will review it. If the court does, the ruling could change, thereby opening new issues in patent claims for manufacturers of diagnostic assays.

Let’s again review the model diagnostic claim to understand the implications of what a reversal of this ruling could mean. The Prometheus case held that if the analyte Y undergoes some sort of transformation before it is detected, then this is enough to establish patentable subject matter. This argument could be extended to say that any antigen-antibody or ligand-receptor reaction that takes place before the detection step might be sufficient to “transform” analyte Y—which could be the antigen, the antibody, the ligand, or the receptor—in such a way that keeps the claim outside of the boundaries of excluded subject matter.

Case Two

Myriad Genetics, a company focused on genetic testing, co-owns patents to genes associated with breast cancer and their diagnostic use (4,5). In a lawsuit brought by the American Civil Liberties Union on behalf of several organizations and patients against Myriad and the U.S. Patent and Trademark Office (6), a federal district court judge made a summary judgment in March 2009, ruling that the patents on the breast cancer genes were invalid because they were granted improperly. In his decision, the judge found the claims to be “unpatentable”, because they involved a “law of nature” and did not embody a patentable “transformation” of the DNA.

In addition to the claims related to the breast cancer genes, the other dispute in this case was whether the claims to a diagnostic analysis or comparison of a patient’s gene sequences were patentable. Myriad argued that, according to the Prometheus decision, you couldn’t analyze or compare the genes unless you “transformed” them in some way to make them comparable. However, the judge disagreed and said that the analysis and comparison steps were just data gathering and did not make the claims patentable.

Going back to our model diagnostic claim, let’s now look at the Myriad patent claims. Myriad’s claims covered methods for detecting gene Y by analyzing it or comparing it to normal gene Z to test for disease X. Since this description did not constitute a “transformation”, the court ruled that the claims were not patentable. Based on this interpretation, one might conclude that diagnostic methods based on identification of mutated genes must include steps that go beyond mere “data gathering”. This case will also continue in the courts, as Myriad has announced it intends to file an appeal within the federal circuit court.

Patents in the Future

Both of these cases highlight the nuances of establishing patentable subject matter in diagnostic method patents. Although they provide some guidance to inventors and lawyers on how to dodge the unpatentability bullet, it’s not so certain what direction that bullet will take in the future as these cases work their way through the appeal process. Until these cases are ultimately decided, patent applications should include a number of claims that vary in scope and recite different bullet proof.


  1. 35 U.S.C. §101 recites that “[w]hoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefore…”
  2. U.S. Patent No. 6,355,623.
  3. Prometheus Labs, Inc. v. Mayo Collaborative Servs., 581 F.3d 1336 (Fed. Cir. 2009).
  4. U. S. Patent No. 5,709,999.
  5. U. S. Patent No. 5,710,001.
  6. Association for Molecular Pathology [AMP] v. USPTO, Myriad Genetics, 2010 U.S. Dist. LEXIS 30629 (S.D.N.Y., March 29, 2010.)

Laurie A. Axford, Esq, is a partner at The Nath Law Group, in San Diego, Calif., and has been an AACC member for 20 years. Email: laxford@nathlaw.com

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