I. Exclusionary principle of patentable subject matter

(i) The exclusionary principle

According to precedents established by the U.S. Supreme Court, there are three exceptions for patentable subject matter under U.S. Patent Act Section 101, namely, the laws of nature, natural phenomena, and abstract ideas. These three exceptions are not found in the US patent statute, but have long been held by the U.S. Supreme Court as an important exception implied in Section. This has been known as patentable subject matter exclusionary principle under the American patent law.

(ii) Legal basis for exclusionary principle of patentable subject matter

The U.S. Supreme Court made an interpretation in Diamond v.Chakrabarty that, “a new mineral discovered in the earth or a new plant found in the wild is not patentable subject matter. Likewise, Einstein could not patent his celebrated E=mc2; nor could Newton have patented the law of gravity. Such discoveries are manifestations of nature, free to all men and reserved exclusively to none.” It also made an essentially same interpretation in Funk Brothers Seed Co. v. Kalo Inoculant Co. that laws of nature, natural phenomena, and abstract ideas were the source of human knowledge and naturally belong to the whole human kind and therefore reserved exclusively to none.

In O’Reilly v. Morse, 56 How. 62 (1854), the Court ruled that the claims of Samuel Morse were non-patentable because it was too broad. U.S. Supreme Court interpreted that “since the claim of the patent involved in the case covers new method in the future, inventor in the future could not use such new method, nor the public have the benefit of it without the permission of this patentee.” It also expressed its concern in its trial of other cases. In Parker v. Flook, 437 U.S. 584 (1978), the Court ruled that the claimed method of the patent involved in the case was just “a formula to calculate the updated alarm limit” and its claims covered “post-solution applications of such a formula in a broad extent.” It held that the claims of the patent involved in Gottschalk v. Benson, 409 U.S. 63 (1972) was “so abstract and sweeping as to cover both known and unknown uses of such mathematical formula” and that “phenomena of nature, though just discovered, mental processes, and abstract intellectual concepts are not patentable, as they are the basic tools of scientific and technological work.” U.S. Supreme Court stated in Bilski v.Kappos that “allowing petitioners to patent risk hedging would preempt use of this approach in all fields, and would effectively grant a monopoly over an abstract idea.”

It can be seen from the above that although it may encourage people to continue to engage in the discovery of the laws of nature by way of granting patent to the laws of nature and others alike, it may also result in a risk that the patent granted to the laws of nature will limit the application of such laws and inhibit the future innovation based on such laws because such laws and principles are generally “basic tools of scientific and technological work.” Some scholars have made an analysis of patentable subject matter exclusionary principle from a perspective of economics. W. Landes and R. Posner make an explanation in their book, The Economic Structure of Intellectual Property Law, that the exclusion of basic truths from patent law reflects “both the enormous potential for rent seeking that would be created if property rights could be obtained in them and the enormous transaction costs that would be imposed on would-be users of those truths.”

In short, if patent were granted to the laws of nature, natural phenomena, and abstract ideas, these basic tools of scientific and technological work would be monopolized, and the possibility of their hindrance to innovation would be much higher than that of their furtherance. Therefore, in accordance with the purpose of patent law, the laws of nature, physical phenomena, abstract ideas and mathematic formula and laws and others alike should be excluded from the scope of patentable subject matter.

II. The Introduction of Mayo v. Prometheus

(i) The patents involved in the case

The patents involved in the case of Mayo were mainly related to the use of thiopurine drugs in the treatment of autoimmune diseases, such as Crohn’s disease and ulcerative colitis. When a patient ingests a thiopurine compound, his body metabolizes the drug, causing metabolites to form in his bloodstream. Because the way in which people metabolize thiopurine compounds varies, the same dose of thiopurine drug affects different people differently, and it has been difficult for doctors to determine whether for a particular patient a given dose is too high, risking harmful side effect, or too low, and so likely ineffective.

At the time the discoveries embodied in the patents were made, scientists have already understood that the levels in a patient’s blood of certain metabolites, including, in particular, 6-thioguanine and its nucleotides (6-TG) and 6-methyl-mercaptopurine(6-MMP), were correlated with the likelihood that a particular dosage of a thiopurine drug could cause harm or prove ineffective. But those in the field had not known the precise correlations between metabolite levels and likely harm or ineffectiveness. The patent claims at issue here set forth processes embodying researchers’ findings that identified these correlations with some precision.

More specifically, the patents-U.S. Patent No. 6,355,623 (623patent) and U.S. Patent No. 6,680,302(302patent)- embodied findings that concentrations in a patient’s blood of 6-TG or of 6-MMP metabolite beyond a certain level (400 and 7000 picomoles per 8x108 red blood cells, respectively) indicated that the dosage was likely too high for the patient, while concentrations in the blood of 6-TG metabolite lower than a certain level (about 230 picomoles per 8x108 red blood cells) indicated that the dosage was likely too low to be effective.

The patent claims sought to embody this research in a set of processes. Both U.S. Court of Appeals for the Federal Circuit and the U.S. Supreme Court took the claim 1 of the 623 Patent as a typical claim to analyze, which describes one of the claimed processes as follows: “A method of optimizing therapeutic efficacy for treatment of an immunemediated 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 230 pmol per 8x108 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 400 pmol per 8x108 red blood cells indicates a need to decrease the amount of said drug subsequently administered to said subject.”

(ii) The procedural posture

Prometheus Laboratories, Inc. (Prometheus), is the sole and exclusive licensee of U.S. Patent No. 6,355,623 (the ’623 patent) and U.S. Patent No. 6,680,302 (the ’302 patent). It sold diagnostic tests that embodied the processes the patents described. For some time, Mayo Clinic Rochester and Mayo Collaborative Services (Mayo), bought and used those tests. But in 2004 Mayo announced that it intended to begin using and selling its own test - a test using somewhat higher metabolite levels to determine toxicity (450 pmol per 8x108 for 6-TG and 5700 pmol per 8x108 for 6-MMP). Prometheus then brought this action claiming patent infringement.

The District Court found that Mayo’s test infringed claim 7 of the ’623 patent. In interpreting the claim, the court accepted Prometheus’ view that the toxicity-risk level numbers in Mayo’s test and the claim were too similar to render the tests significantly different. The court ruled that the number Mayo used (450) was too close to the number the claim used (400) to matter given appropriate margins of error. The District Court also accepted Prometheus’ view that a doctor using Mayo’s test could violate the patent even if he did not actually alter his treatment decision in the light of the test. In doing so, the court construed the claim’s language, “indicates a need to decrease” (or “to increase”), as not limited to instances in which the doctor actually decreases (or increases) the dosage level where the test results suggest that such an adjustment is advisable. Nonetheless the District Court ultimately granted summary judgment in Mayo’s favor. The court reasoned that the patents effectively claim natural laws or natural phenomena - namely the correlations between thiopurine metabolite levels and the toxicity and efficacy of thiopurine drug dosages - therefore are not patentable. Prometheus appealed to U.S. Court of Appeals for the Federal Circuit which reversed the judgment rendered by the District Court. The Appeal Court pointed out that in addition to these natural correlations, the claimed processes specify the steps of “administering a (thiopurine) drug” to a patient and “determining the resulting metabolite level.” These steps, it explained, involved the transformation of the human body or of blood taken from the body. Thus, the patents satisfied the standard of “machine or transformation test” set forth by U.S. Court of Appeals for the Federal Circuit in the past, which the court thought sufficient to “confine the patent monopoly within rather definite bounds,” thereby bringing the claims into compliance with §101 of U.S. Patent Act.

Mayo filed a petition to the U.S. Supreme Court for certiorari, which was granted. The Court vacated the judgment, and remanded the case for reconsideration in light of Bilski, which clarified that the “machine or transformation test” is not a definitive test of patent eligibility, but merely an important and useful clue. On remand, the Federal Circuit reaffirmed its earlier conclusion. It ruled that even if the “machine-or-transformation test” is understood merely as an important and useful clue, it can still lead to the “clear and compelling conclusion that the claims do not encompass laws of nature or preempt natural correlations.” Mayo again filed a petition for certiorari, which U.S. Supreme Court granted.

III. Detailed analysis of the claims of Mayo case

It is required that doctors should determine whether a particular dosage of a thiopurine drug is too high or too low for a particular patient with immune disorder. The claims of the patent involved in the case applied for the protection of the foresaid method used by doctors. It has been mentioned above that there are 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 and the claims of the patent involved in the case made a utilization of such laws of nature. Prometheus’ patents set forth laws of nature - namely, 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. Claim 1, for example, states that if the levels of 6-TG in the blood of a patient who has taken a dose of a thiopurine drug exceed about 400 pmol per 8x108 red blood cells, then the administered dose is likely to produce toxic side effects. 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. The question for further determination 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 patenteligible processes that apply natural laws?

(i) The addition of new contents has been a common practice

If the laws of nature are unpatentable, then the method which cited the laws of nature can not be patented neither, unless the method has some other contents which can help to ensure that the method not merely tries to monopolize the law of nature itself by drawing support from patent drafting skills. The claim involved in the case contains an “administering” step, a “determining” step, and a “wherein” step. These additional steps themselves are not natural laws but neither are they sufficient to transform the nature of the claim.

First, the “administering” step simply refers to the relevant audience, namely doctors who treat patients with certain diseases with thiopurine drugs and patients with such diseases. That audience is a pre-existing audience and doctors had used thiopurine drugs to treat patients suffering from autoimmune disorders long before anyone asserted these claims. In any event, the “prohibition against patenting abstract ideas ‘cannot be circumvented by attempting to limit the use of the formula to a particular technological environment.’”

Second, the “wherein” step simply tells a doctor about the relevant natural laws, at most adding a suggestion that he should take those laws into account when treating his patient. That is to say, these steps tell the relevant audience about the laws while trusting them to use those laws appropriately where they are relevant to their decision making, which is very much like Einstein telling linear accelerator operators about his basic law and then hoping them to use it when necessary.

Third, the “determining” step tells the doctor to determine the concentrations of the relevant metabolites in the blood, through whatever process the doctor or the laboratory wishes to use. As the patents stated, methods for determining metabolite levels were well known in the art. Indeed, scientists routinely measured metabo l i t e s as part of t h e i r investigations into the relationships between metabolite levels and efficacy and toxicity of thiopurine compounds. Thus, this step tells doctors to engage in well-understood, routine, conventional activity previously engaged in by scientists who work in the field. Purely “conventional or obvious” “pre-solution activity” is normally not sufficient to transform an unpatentable law of nature into a patent-eligible application of such a law.

Last, to consider the three steps as an ordered combination adds nothing to the laws of nature that is not already present when the steps are considered separately. Such combination would no longer exist if these steps were examined individually. Anyone who wants to make use of these laws must first administer a thiopurine drug and measure the resulting metabolite concentrations of his patient, and so the combination amounts to nothing significantly more than an instruction to doctors to apply the applicable laws when treating their patients.

U.S. Court of Appeals for the Federal Circuit, in upholding the patent eligibility of the claims of the patent involved in the case, relied on the judgment rendered by U.S. Supreme Court in the past that “transformation and reduction of an article ‘to a different state or thing’ is the clue to the patentability of a process claim that does not include particular machines.” U.S. Court of Appeals for the Federal Circuit ruled that the claimed processes are eligible patent because they involve transforming the human body by administering a thiopurine drug and transforming the blood by analyzing it to determine metabolite levels.

The U.S. Supreme Court ruled as follows: The first of these transformations, however, is irrelevant. As we have pointed out, the “administering” step imply helps to pick out the group of individuals who are likely interested in applying the law of nature. And the second step could be satisfied without transforming the blood, should science develop a totally different system for determining metabolite levels that did not involve such a transformation. Regardless, in stating that the “machine-or-transformation” test is an “important and useful clue” to patentability, we have neither said nor implied that the test trumps the “law of nature” exclusion. That being so, the test fails here.

A conclusion can be drawn from the above analysis that the three steps stated by the claims involved in the case simply tell doctors to gather data from which they may draw an inference in light of the correlations. To put the matter more succinctly, the claims inform a relevant audience about certain laws of nature; any additional step consists of well-understood, routine, conventional activities 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, the steps are not sufficient to transform unpatentable natural correlations into patentable applications of those regularities.

(ii) The added contents are too broad

The laws of nature at issue here are narrow laws that may have limited applications, but the patent claims that embody them nonetheless implicate this concern. They tell a treating doctor to measure metabolite levels and to consider the resulting measurements in light of the statistical relationships they describe. In doing so, they tie up the doctor’s subsequent treatment decision whether that treatment does, or does not, change in light of the inference he has drawn using the correlations.

The “determining” step is set forth in too highly general language which covers all processes that make use of the correlations after measuring metabolites, including later discovered processes that measure metabolite levels in new ways. And they threaten to inhibit the development of more refined treatment recommendations that combine Prometheus’ correlations with later discovered features of metabolites, human physiology or individual patient characteristics.

As mentioned above, the steps included in the claims add nothing of significance to the natural laws themselves. That is to say, unlike atypical 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. The processes included in the patent claims are not eligible patent because they tie up too much future use of laws of nature.

IV. Exploration and Conclusion

American precedents require that patent should not be granted according to the interpretation based on the skills of patent drafter while turning blind eyes to those principles that patent shall not be granted to the laws of nature, and that no patent should be granted to method where the protection of its claims is so broad that it will monopolize the application of such laws of nature. For those method patents mainly relying on the use of the laws of nature, it is required to contain other elements or the combination of elements in order to ensure such method patent is not the laws of nature. The claims of the case of Mayo can not meet the above requirements. From a negative perspective, all other contents included in the claims are well-understood, routine, conventional activities previously engaged in by scientists in the field if the laws of nature are excluded from the operation steps. Meanwhile, if the court upholds such method to be granted a patent, the further application of such method would be limited, result in a risk of hampering the application of the laws of nature, and there would be a serious negative proportion between such risk and its promotion in scientific and technological advancement. From a positive perspective, all other contents would not transform claims into a practical and concrete application of the laws of nature after the exclusion of such laws from operation steps. Therefore, a comprehensive consideration will draw a conclusion that the claims involved in the case are unpatentable.

(Translated by Yuan Renhui)