In its latest case on patent eligibility, Mayo Collaborative Services v. Prometheus Laboratories the Court reiterated that laws of nature are not patent eligible, gave little guidance as to what it meant by “law of nature” other than that the Court was concerned about claims that were too broad and referred us to its prior decisions, especially Diamond v. Diehr again for guidance.

A typical claim (claim 1 of US 6,355,623) in Prometheus’s patent reads:

1. A method of optimizing therapeutic efficacy for treatment of an immune-mediated gastrointestinal disorder, comprising:

(a) administering a drug providing 6-thioguanine to a subject having said immune-mediated gastrointestinal disorder; and

(b) determining the level of 6-thioguanine in said subject having said immune-mediated gastrointestinal disorder,

wherein the level of 6-thioguanine less than about 230 pmol per 8 x108 red blood cells indicates a need to increase the amount of said drug subsequently administered to said subject and

wherein the level of 6-thioguanine greater than about 400 pmol per 8.x 108 red blood cells indicates a need to decrease the amount of said drug subsequently administered to said subject.

The Supreme Court in a unanimous opinion written by Justice Breyer saw the claim as comprising a law of nature in the form of “relationships between concentrations of certain metabolites in the blood and the likelihood that a dosage of thiopurine drug will prove ineffective or cause harm”. The other elements of the claim were regarded as “routine conventional activity already engaged in by the scientific community and these steps when viewed as a whole add nothing significant beyond the sum of their parts taken separately”.

Breyer J noted:

If a law of nature is not patentable, then neither is a process reciting a law of nature, unless that process has additional features that provide practical assurance that the process is more than a drafting effort designed to monopolize the law of nature itself. A patent, for example, could not simply recite a law of nature and then add the instruction “apply the law.”

Breyer J distinguished the present case from Diamond v. Diehr (a case where the Supreme Court had held that use of the Arrhenius equation to control a method for curing rubber was patentable even though the Arrehenius equation itself was not) as follows:

The Court pointed out that the basic mathematical equation, like a law of nature, was not patentable. But it found the overall process patent eligible because of the way the additional steps of the process integrated the equation into the process as a whole. Those steps included“installing rubber in a press, closing the mold, constantly determining the temperature of the mold, constantly re-calculating the appropriate cure time through the use of the formula and a digital computer, and automatically opening the press at the proper time.” It nowhere suggested that all these steps, or at least the combination of those steps, were in context obvious, already in use, or purely conventional.

This is true. In Diehr, the Court never commented on whether the extra steps were obvious or not. What it did say was

In determining the eligibility of respondents’ claimed process for patent protection under§101, their claims must be considered as a whole. It is inappropriate to dissect claims into old and new elements and then ignore the presence of the old elements in the analysis.

The Court has, however, been consistent in holding that “insignificant post-solution activity will not transform an unpatentable principle (or law of nature) into a patentable process”.

The Mayo decision therefore poses two problems: 1) what is a law of nature and 2) if a method utilizes a law of nature when does insignificant post solution activity become patent eligibility-creating non-conventional activity.

Having regard to the first point, reading the term “law of nature” as broadly as Breyer J. did in the present case, seems to lead to the conclusion that almost all method inventions (apart from business methods which have their own problems) fall within the definition. It is natural for chemicals to react when put together. It is natural for electrons to flow through a conductor. What Breyer J.’s opinion fails to recognize is that it is not natural to choose which chemicals to react or through what particular conductors electrons should be caused to flow, or dare one say it, what particular metabolites to monitor when seeking to adjust dosages of thipurines to give to a patient.

Under the Breyer analysis, this question of selection will apparently have to be addressed when considering whether other steps set out in a claim are conventional or not. At first glance, it would seem that Breyer J.’s opinion leaves little room for this. However, apparently realizing the problems that a broad interpretation of the decision would cause, he goes on to state:

We need not, and do not, now decide whether were the steps at issue here less conventional, these features of the claims would prove sufficient to invalidate them. For here, as we have said, the steps add nothing of significance to the natural laws themselves. Unlike, say, a typical patent on a new drug or a new way of using an existing drug, the patent claims do not confine their reach to particular applications of those laws.

So, had the claim been written as a method of treating an immune-mediated gastrointestinal disorder with a thiopurine and adjusting the dose in accordance with the results of a determination of 6-thioguanine levels in the blood, would the Supreme Court have come to a different conclusion? Who can say? But it is probably worth a try. Otherwise, there would seem to be a problem in securing patent protection for new methods of diagnosis.

What the Supreme Court has made clear, however, both in Bilski and Mayo is its concern that broad patent claims may impeded future research. The issue is not new. Section 2 of the 1793 Act specifically dealt with it by pointing out that the inventor of an improvement patent could not use that improvement without the consent of the owner of the dominant patent. The issue is, however, one that keeps on coming up. Indeed the Federal Circuit’s approach to written description and the need for the specification to show “possession” of the invention as set out in Ariad Pharmaceuticals, Inc et. al v. Eli Lilly and Co. can be seen as an example of the same concern. In Mayo, Breyer J. expresses the concern as follows:

there is a danger that the grant of patents that tie up their use will inhibit future innovation premised upon them, a danger that becomes acute when a patented process amounts to no more than an instruction to “apply the natural law,” or otherwise forecloses more future invention than the underlying discovery could reasonably justify.

This is a slippery slope. How does one determine what is “reasonably justified”? In England, Lord Hoffman adopted this approach in the House of Lord’s decision 1997 in Biogen v. Medeva. Ten years later he deliberately stepped down to the Court of Appeal to deliver the judgment in Lundbeck v. Generics to explain that this approach was not universally applicable.

If there is one conclusion that can be drawn from Bilski and Mayo, however, it is that the Supreme Court dislikes broad claims and not receiving any suitable cases under 35 USC 112 on which to express this, has taken the opportunity of cases under 35 USC 101 to do so. This is unfortunate since deciding a policy issue on the basis of an inappropriate part of the statute almost invariably leads to unforeseen consequences.