High Standards for Patentable Diagnostic Tests in the Era of Personalized Medicine

Staff Writer

On March 20, 2012, the U.S. Supreme Court unanimously held that Prometheus Laboratory Inc.’s (“Prometheus”) diagnostic process to determine the appropriate level of thiopurine drugs for a patient is not patentable. Thiopurine drugs are used to treat autoimmune diseases. Because each person metabolizes thiopurine at different rates, physicians struggle to determine an appropriate therapeutic dose for a particular patient. Doses that are too high will cause toxic side effects, while doses that are too low will not be therapeutically effective. Prometheus patented a test for determining the precise correlations between how a patient metabolizes thiopruine and what is the appropriate dose for that patient. Although Mayo Clinic Rochester and Mayo Collaborative Services (“Mayo”) had previously used Prometheus’ test, in 2004 it announced an intention to use and sell its own test, which would be similar to the Prometheus test, but with higher metabolite levels. Prometheus sued Mayo for patent infringement. The District Court found that Mayo’s test infringed upon Prometheus’ patents but held that the process claimed in the patents was simply “natural laws or natural phenomena” and thus not patentable. No. 04cv1200 JA, 2008 WL 878910 (S.D. Cal. 28 Mar., 2008). The Federal Circuit Court of Appeals reversed based on a finding that the process was patentable eligible under the “machine or transformation test.” 581 F.3d 1336, 1342-43. Mayo appealed the case to the U.S. Supreme Court, who remanded it to the Federal Circuit Court to apply its holding in Bilski v. Kappos, 561 U. S. ___, that the “machine or transformative test is not a dispositive test of patent eligibility. The Federal Circuit reaffirmed their holding that Prometheus’ processes were patentable.
Mayo appealed again and the U.S. Supreme Court unanimously reversed the Federal Circuit in holding the process not patent eligible. The Court began by noting that the “‘laws of nature, natural phenomena, and abstract ideas’ are not patentable subject matter under §101 of the Patent Act, Diamond v. Diehr, 450 U. S. 175, 185, (1981), [but] ‘an application of a law of nature . . . to a known structure or process may [deserve] patent protection.’” Mayo Collaborative Services, DBA Mayo Medical Laboratories, Et al., Petitioners v. Prometheus Laboratories, Inc., 566 U. S. ____ (2012).
The Court found that Prometheus’ claim was akin to Parker v. Flook, 437 U. S. 584, 594 (1978). In Flook, the Court held that the chemical processes at issue were “well known” such that “there was no ‘inventive concept’ in the claimed application of the formula” as the additional steps did not integrate the natural processes into a particular application. Like Flook, Prometheus’ claim is not patent eligible because the process of analyzing how a body metabolizes thioprine is well know in the scientific field and Prometheus was simply directing the test to physicians for use while treating patients
The Court further held that the specific Prometheus test process adds nothing to the natural laws underlying the test. To allow the Prometheus’ correlation test to be patented may prevent future discovery that may result in more refined thioprine treatment models.
The Court was unconvinced by Prometheus’ argument that barring patents such as its own will discourage companies from exploring “new diagnostic laws of nature.” This case reaffirms legal precedent that natural laws, no matter how narrow, may not be patented. However, in the era of personalized medicine where discovering specific natural laws can transform individual medical treatments, the case has critical implications for how biomedical and pharmaceutical companies draft patent applications for diagnostic tests. No longer is it sufficient to simply discover new, narrow laws of nature and then create a process of applying this to medical treatment. Rather, scientists will have to integrate the law holistically into a specific application in a manner that actually contributes something meaningfully novel.

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