In a unanimous decision on March 20, 2012, the Supreme Court struck down patent claims for a diagnostic method, ruling that the claims are too closely tied to a law of nature. Specifically, in Mayo Collaborative Services v. Prometheus Laboratories, Inc., the Court invalidated patent claims directed to a diagnostic method employing a blood test to determine appropriate dosage of a thiopurine drug, used in the treatment of autoimmune diseases.

Prometheus started as a typical infringement case. Prometheus, the exclusive licensee of the patents, asserted them against a former licensee for selling a diagnostic kit allegedly covered by the patent claims. The trial court held that the patents were invalid because directed to subject matter that is not eligible to be patented, namely, natural laws or natural phenomena. The Federal Circuit reversed in a decision we reported here, and the Supreme Court granted review.

In Prometheus, the patent claimed an inventive discovery in the observation that when blood levels of a particular metabolite of an administered thiopurine drug fall outside a specific range, the dosage of the drug will be either ineffective (when too little has been administered) or harmful (when too much has been administered). The patent claims, like other medical diagnostic claims, included a measuring step (e.g., measuring the level of 6-thioguanine in the blood of a subject) and an inferential step (i.e., if the level is outside the desired range, the drug dosage is either too low or too high).

The claims added a step often lacking in medical diagnostic claims, that of administering thiopurine to the subject. It was this administering step along with the measuring step that led the Federal Circuit to hold that the claims inPrometheus were “transformative” of a law of nature, and thus patent-eligible subject matter under the Supreme Court’s Bilski opinion, which we reported here.

In a decision authored by Justice Breyer, the Supreme Court overturned the Federal Circuit, and held that the Prometheus claims were not transformative of the underlying laws of nature and were therefore not patentable subject matter:

While it takes a human action (the administration of a thiopurine drug) to trigger a manifestation of this relation in a particular person, the relation itself exists in principle apart from any human action. The relation is a consequence of the ways in which thiopurine compounds are metabolized by the body—entirely natural processes. And so a patent that simply describes that relation sets forth a natural law.

In the Court’s view, the administering step in the Prometheus claims was not transformative because the “administering” step simply refers to doctors who treat patients with thiopurine. The measuring step was also given no weight because it merely tells doctors to “engage in well-understood, routine, conventional activity previously engaged in by scientists who work in the field.”

In summary, the Court stated:

[T]he claims inform a relevant audience about certain laws of nature; any additional steps consist of well understood, routine, conventional activity already engaged in by the scientific community; and those steps, when viewed as a whole, add nothing significant beyond the sum of their parts taken separately. For these reasons we believe that the steps are not sufficient to transform unpatentable natural correlations into patentable applications of those regularities.

Justice Breyer fears that allowing patents that tie up the use of laws of nature will foreclose future innovation derived from those laws.

Because the patents recite “relationships between concentrations of certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove ineffective or cause harm,” Justice Breyer says they recite “laws of nature.” In fact, the patent claims require administration of a man-made drug, an activity that manifestly does not occur in nature.

Put another way, the patent claims demonstrably do not cover “laws of nature” because they are limited to a method of determining dosage adjustment, not in the abstract, but for a man-made drug that is actually administered. The facile rhetoric of the opinion goes beyond what its facts require.

The friend-of-court brief filed by the Solicitor General of the United States (with participation of attorneys from the U.S. Patent and Trademark Office) had urged the Supreme Court to take a different view of patent-eligible subject matter, positing that patent eligibility should not be a major barrier to getting a patent once it is clear that the patent claims do not simply recite a law of nature per se.

The Solicitor General had, as summarized by the Court, argued on behalf of the United States that “other statutory provisions—those that insist that a claimed process be novel, 35 U. S. C. §102, that it not be ‘obvious in light of prior art,’ §103, and that it be ‘full[y], clear[ly], concise[ly], and exact[ly]’ described, §112—can perform this screening function. In particular, it argues that these claims likely fail for lack of novelty under §102.”

Justice Breyer rejected this approach, however, owing to a concern that it “would make the ‘law of nature’ exception to §101 patentability a dead letter.”

The approach taken by Prometheus tracks an obscure patent decision of the Court in 1948 written by Justice Douglas, Funk Bros. Seed Co. v. Kalo Inoculant Co, a case carefully distinguished by the Court in later decisions, and also cited with approval by Justice Breyer in Prometheus. The inventor in Funk Bros. “discovered that there are strains of each species of root-nodule bacteria which do not exert a mutually inhibitive effect on each other” and developed “a mixed culture of Rhizobia capable of inoculating the seeds of plants belonging to several cross-inoculation groups.”

Justice Douglas asserted that the discovery that certain strains of distinct species of bacteria can be mixed without a mutually inhibitory effect is “no more than the discovery of some of the handiwork of nature and hence is not patentable.” In other words, the discovery is not patent-eligible subject matter.

Having established the principle that the discovery is not patentable, Justice Douglas turned to the application of the discovery, and was unimpressed. “But however ingenious the discovery of that natural principle may have been, the application of it is hardly more than an advance in the packaging of the inoculants.” He pointed out that the bacteria in the mixture function in exactly the same way as bacteria always functioned, “quite independently of any effort of the patentee.”

In a final flourish, after snuffing the life out of the patent claims by characterizing them as based on an unpatentable discovery, Justice Douglas said that they were not directed to subject matter that was inventive as required by the 1941 Supreme Court decision in Cuno Engineering Corp. v. Automatic Devices Corp.

Breyer’s logic in Prometheus is similar: Associate a law of nature with a key aspect of the claims to exclude them from patentability, then find the remaining claim limitations to be conventional. Although the opinion did not actually reach the question whether the subject matter claimed is non-obvious (the criterion replacing the “inventive” requirement at the time of Cuno Engineering), the result in Prometheus is similar—invalid claims.

The flaw in this analysis is that, as the Federal Circuit observed in its landmark State Street decision, all inventions use science and engineering principles—laws of nature—for their implementation, but inventions typically apply these principles to achieve a practical effect. The practical effect in the patents in Prometheus is a determination whether there should be a change in drug dosage. Once a claim limitation is directed to the practical effect, the claim is no longer directed broadly to a law of nature.

Prometheus is not the first opinion in which Justice Breyer has spoken on the subject of diagnostic method claims, but it is the first time he brought a majority (and indeed all) of the Court’s justices along with him. In Laboratory Corp. of America Holdings v. Metabolite Laboratories Inc., a one-line decision from 2006, the Court’s majority dismissed the case to which it had granted review, but Justice Breyer, joined by Justices Stevens and Souter, wrote a lengthy dissent.

The diagnostic method claim in Lab. Corp. was similar to the claims presented inPrometheus, except that the claim lacked a step of administering a drug. The dissenters took the position that “the correlation between homocysteine and vitamin deficiency set forth in claim 13 is a ‘natural phenomenon’.” Furthermore: “Claim 13’s process instructs the user to (1) obtain test results and (2) think about them. Why should it matter if the test results themselves were obtained through an unpatented procedure that involved the transformation of blood?”

Expanding on this position, the dissenters proclaimed that “the process is no more than an instruction to read some numbers in light of medical knowledge.… And here, aside from the unpatented test, they [the steps of the claim] embody only the correlation between homocysteine and vitamin deficiency that the researchers uncovered. In my view, that correlation is an unpatentable ‘natural phenomenon,’ and I can find nothing in claim 13 that adds anything more of significance.”

The Lab. Corp. dissent suggested that the medical profession is being unfairly saddled with restrictions imposed by this patent, which, along with others, “may inhibit doctors from using their best medical judgment.” While in the minority inLab. Corp., Justice Breyer wrote for a unanimous court in Prometheus.

Because many diagnostic tests depend on a blood test followed by an analysis of the blood test results, patent claims directed to them will be likely targets of patent invalidity attacks after Prometheus. The decision also calls into question the patentability of the claims in Ass’n for Molecular Pathology v. US Patent and Trademark Office, a case decided last year by the Federal Circuit involving patent claims of Myriad Genetics. (We reported on that decision here.)

The Myriad patents include some method claims held patent-ineligible by the Federal Circuit, as well as composition-of-matter claims to isolated DNA and a single patent claim directed to a method for screening potential cancer therapeutics that the Federal Circuit held to be patent-eligible. On March 26, 2012 the Supreme Court remanded the case to the Federal Circuit for reconsideration in light of Prometheus.

Indeed, patent claims directed to methods of treatment—by extension of the rationale in Prometheus—might also be subject to attack. After all, a typical method-of-treatment claim has a fairly straightforward structure: “A method of alleviating the symptoms of disease A in a subject by administering a compound X to the subject in need thereof, so that the symptoms of the subject are alleviated as compared to a subject to which the compound X was not administered.”

Thus, method-of-treatment claims, like the Prometheus claims, contain an administering step without much more. One can expect an argument that a subject’s reaction to the administered compound, namely alleviation of disease symptoms, is a law of nature under Prometheus.

Although the Court has narrowed the scope of patent eligibility, Justice Breyer provides something of a tip for avoiding rejection or invalidation, based on patent ineligibility, with these words: “The question before us is whether the claims do significantly more than simply describe these natural relations. To put the matter more precisely, do the patent claims add enough to their statements of the correlations to allow the processes they describe to qualify as patent-eligible processes that apply natural laws?”

The problem with the Prometheus patent claims boils down to lack of sufficient structure in the claims. The claims required administration of a drug, then a blood test, then a greater-than, less-than analysis of the blood test results. That was not enough. The analysis step did not impress the Court because it viewed the observed correlation as a “rule of nature.” The drug administration step did not strike the Court as an additional claim element because the drug was already being administered in the prior art.

The day after the Prometheus decision, the Patent and Trademark Office issued preliminary guidelines for examiners. The guidelines, following the line of analysis above, instruct examiners as follows:

“Examiners must continue to ensure that claims, particularly process claims, are not directed to an exception to eligibility such that the claim amounts to a monopoly on the law of nature,natural phenomenon, or abstract idea itself. In addition, to be patent-eligible, a claim that includes an exception should include other elements or combination of elements such that, in practice, the claimed product or process amounts to significantly more than a law of nature, a natural phenomenon, or an abstract idea with conventional steps specified at a high level of generality appended thereto.” (emphasis in original).

If patent claims to such diagnostic tests do not include more claim limitations than those in the Prometheus patents, such claims risk being invalidated under Prometheus. Those seeking to obtain patent coverage for diagnostic tests are advised to develop tests that require more structure.

Instead of a simple blood test, it would be preferable to develop a dedicated machine, or a disposable device, on which blood is deposited, which then runs an analysis in some automated fashion and produces a user-readable output. Patent claims directed to such a machine or device would likely fare better than the patent claims in Prometheus because there is more structure and because the alleged “law of nature” has been harnessed to a machine or device.

There is an irony to this result. Does the Prometheus ruling in fact stimulate “future innovation” as imagined by the Court? If diagnostic companies experience greater difficulty in getting patent protection for their innovations, they will have corresponding difficulty in getting financing to commercialize their products. In truth, we can expect fewer innovative diagnostic tests.

Perhaps by making a more expensive diagnostic machine or device—as opposed to a diagnostic test—a company may have a chance of recouping its investment. The cost per test conducted on such a machine would likely be greater than the cost per test without a machine or device. So if innovative diagnostic tests are introduced, one may reasonably expect them to be more costly.

After the 1941 Supreme Court decision in Cuno Engineering interposed a “flash of creative genius” test for patentability, Congress amended the patent law to overrule the Supreme Court and introduced the standard of non-obviousness, which still applies today. If companies in the diagnostics business are sufficiently aroused by the decision in Prometheus, they may seek redress from Congress, which was energized to modernize U.S. patent law last year with passage of the America Invents Act. We expect to hear more on this issue.