It's only natural
Supreme Court rejects patents on diagnostic test

Medical researchers are sometimes accused of playing God. But there's at least one place where they can't get away with that: in the patent arena. As the U.S. Supreme Court's recent decision in Mayo Collaborative Svcs. v. Prometheus Laboratories, Inc. reminds us, the laws of nature — as well as some processes that purport to apply them — aren't patentable.

3-step process

Prometheus Laboratories held an exclusive license on two patents that involve the use of thiopurine drugs to treat autoimmune diseases. When ingested by a patient, the body metabolizes the drugs, producing metabolites in the bloodstream.

Because patients metabolize the drugs differently, doctors had found it difficult to determine whether a particular patient's dose was too high (which could harm the patient) or too low (which would probably be ineffective). To identify correlations between metabolite levels and the likely harm or ineffectiveness with precision, the patents used a three-step process:

1. Administering, which instructs a doctor to administer the drug to the patient,
2. Determining, which instructs the doctor to measure the resulting metabolite levels in the patient's blood, and
3. Wherein, which describes the metabolite concentrations above which there's a likelihood of harmful side effects and below which it's likely the dosage is ineffective. This step also informs the doctor of the need to decrease or increase dosage.

Using the patented method, Prometheus sold a diagnostic test kit to doctors and hospitals to help them determine proper dosage levels of thiopurine. Mayo Collaborative Services initially bought and used the tests but eventually announced that it intended to sell and market its own, somewhat different, diagnostic test. Prometheus sued Mayo for infringement.

Back and forth

The district court found that Mayo's test infringed the patents but determined that the patents were invalid because they claimed unpatentable laws of nature — specifically, the correlations between metabolite levels and the toxicity and efficacy of thiopurine drugs. The Federal Circuit reversed, finding that the processes were patentable under the "machine or transformation test." The test requires either that the method in the claim be performed with a "machine" or that performance of the method transforms something in the tangible world.

But, after the Supreme Court ruled in Bilski v. Kappos that the machine or transformation test isn't the definitive test of patent eligibility, it remanded this case back to the Federal Circuit for reconsideration. The Federal Circuit reaffirmed its earlier conclusion, and Mayo appealed.

Entirely natural

The Supreme Court began its review by noting its longstanding position that, while laws of nature, natural phenomena and abstract ideas aren't patentable, "an application of a law of nature or mathematical formula to a known structure or process may well be deserving of patent protection." The Court, however, made clear that, to transform an unpatentable law of nature into a patent-eligible application of such a law, one must do more than simply state the law of nature while adding the words "apply it."

Here, the patents purported to apply natural laws describing the relationships between the concentration in the blood of certain thiopurine metabolites and the likelihood that the drug dosage will be ineffective or induce harmful side effects. While it takes a human action (the administration of a thiopurine drug) to trigger a manifestation of this relationship, the relationship is a consequence of the ways in which thiopurine compounds are metabolized by the body. That's an entirely natural process.

Court defines "patentable"

The Court was, therefore, tasked with determining whether the claimed processes transformed these unpatentable natural laws into patent-eligible applications of those laws. And its answer was no.

To be patentable, the Supreme Court explained, the claimed processes must have additional features that provide practical assurance that the processes are a genuine application of the natural laws, rather than a patent-drafting tactic intended to monopolize the law of nature itself. It found that the three steps set forth in the patent claims, while not themselves natural laws, were insufficient to transform unpatentable natural correlations into patentable applications of those correlations. The steps simply told doctors to gather data from which they might draw an inference in light of the correlations.

The Supreme Court concluded that the claims merely informed a relevant audience about certain laws of nature. Any additional steps consisted of well-understood, routine, conventional activity already engaged in by the scientific community. Those steps, when viewed as a whole, added nothing significant.

Wider implications

The Supreme Court's reasoning in this case could have wider implications. For example, it may also apply to the mathematical algorithms commonly used in software patents. But just how widely the application of Mayo will extend remains to be seen. •