American Association for Clinical Chemistry
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May 2011 Clinical Laboratory News: Patentability of Diagnostic Method Claims

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May 2011: Volume 37, Number 5


Patentability of Diagnostic Method Claims
New Court Ruling is Good News for Manufacturers, but for How Long?

By Brian S. Sun, Esq.

The medical diagnostics field scored a key victory on December 17, 2010 when the U.S. Court of Appeals for the Federal Circuit reaffirmed its prior holding in Prometheus Laboratories, Inc. v. Mayo Collaborative Services, (“Prometheus II”), finding in favor of patent eligibility of diagnostic applications based on what is known as the “machine or transformation” test.

Patents protect inventors from having their inventions copied by other parties. For example, when a company creates a new diagnostic assay, it attempts to protect its invention by asserting certain claims in a patent filing. But a fundamental question being argued today in U.S. Courts is what can and cannot be protected under existing patent law.

One patent lawsuit in particular—Prometheus Laboratories, Inc. v. Mayo Collaborative Services—has been closely watched by diagnostic manufacturers. Prometheus, a specialty pharmaceutical company, holds a method of treatment patent for administering and monitoring thiopurine, a drug used to treat inflammatory bowel diseases. To maintain therapeutic levels of the drug, clinicians monitor patients for thiopurine metabolites and adjust the drug dosage accordingly. Prometheus’s patent included claims for administering the drug, as well as determining levels of its metabolites.

In March 2008, a District Court decided that Prometheus’s method of treatment claims were not patentable, characterizing the administration and determination steps as merely necessary data-gathering steps. But the Federal Circuit disagreed, holding that the steps could be patented so long as the machine or transformation test is met, which considers whether a machine or a procedure specifically designed to carry out a process transforms an entity from one thing to another. After a short trip to the Supreme Court, where the Federal Circuit’s decision was vacated and remanded for reconsideration, the Federal Circuit reaffirmed its prior ruling, finding that steps of administering and determining metabolite levels are in fact “transformative.”

The Machine or Transformation Test

What is especially noteworthy about the Prometheus II ruling is that the Federal Circuit Court applied the machine or transformation test and decided that administering a drug like thiopurine is transformative of the human body, regardless of the fact that the transformation occurs according to natural biological processes. Furthermore, in addressing claims that only contain a determining step, the Court also found them to be transformative because “some form of manipulation” is necessary to extract drug metabolites from a subject, such as high pressure liquid chromatography, the method used to analyze the thiopurine metabolites. This is good news for medical diagnostics claims, which usually feature some sort of separation and/or manipulation of chemical species.

The Impact of This Ruling

The decision in Prometheus II is important for several reasons. First, the Court established a distinction between claims that are directed to natural phenomena and claims that are directed to applications of naturally occurring phenomena, such as providing a “determining” step to identify a correlation. In particular, the Court cited In re Grams, a prior case that involved determining correlations of an abnormality by using an algorithm, stating that performance of diagnostic tests on individuals are transformative.

Based on the Court’s decision, it also appears that the machine or transformation test is fulfilled so long as there is a determining step involving some form of chemical or biological manipulation. In support of this distinction, the Court credited Prometheus’s expert, who testified that “at the end of the process, the human blood sample is no longer human blood.”

Another critical point the Court addresses in its decision is the question of “mental steps” in claims, and whether such steps in combination with transformative steps confer patent eligibility. At issue were two final “wherein” clauses in the claims that described “mental processes used to determine the need to change the dosage levels of the drugs.” In what is another favorable outcome for medical diagnostics, the Court held that mental steps, while patent ineligible per se, do not “negate the transformative nature of prior steps.” What this means is that patent claims must be evaluated as a whole, and the fact that mental steps are recited in part of the claims cannot be used to exclude them from patent eligibility.

Foreshadowing for Myriad?

Another case involving diagnostics that was appealed to the Supreme Court and subsequently sent back to the Federal Circuit is the Myriad Genetics case. Centered on patents covering breast cancer genes and diagnostic tests for identifying mutations in the genes, Myriad will be a landmark case in determining the patent eligibility of so-called gene patents. The key issue in this case that pertains to diagnostics is whether the method claims for extracting and analyzing a subject’s DNA sequences meet the machine or transformation test.

Although the recent ruling in Prometheus II is more or less a reiteration of the previous ruling in this case, the Court’s rationale offers some intriguing insight as to how the Court might decide in the controversial Myriad case. Given the broad interpretation applied to the “machine or transformation” test in Prometheus II, and in view of the narrow interpretation of the machine or transformation test applied at the District Court level, it seems likely that the Federal Circuit will conclude that Myriad’s diagnostic claims are patent eligible. Furthermore, the Court’s interest in identifying the essence of a claimed invention suggests that Myriad’s claims may be found to be patentable based on a public policy rationale. Such a decision will be vital for establishing eligibility of gene patents in the future.

What’s Next?

While the ruling in the Prometheus II case is good news for medical diagnostic companies, the current elation might soon change. The case will almost certainly be appealed to the Supreme Court, where the Court might tighten the reins on patent eligibility of diagnostic claims. The medical diagnostic industry, while enjoying the benefits of the ruling in Prometheus II, should continue to stay tuned for the ultimate verdict, which the Supreme Court could issue as soon as 2012.


Brian Sun is an associate patent attorney at the Nath Law Group, Carlsbad, Calif. Email: bsun@nathlaw.com