The recent US Supreme Court decision in Prometheus Labs impacts the patentability of medical diagnostic method claims specifically and, more generally, any method claim relying on a correlation based on a law of nature. In a unanimous ruling, the Supreme Court held that Prometheus' process for determining the proper dosage of thiopurine drugs to treat autoimmune diseases is not patentable subject matter under 35 U.S.C. § 101. Mayo Collaborative Servs. v. Prometheus Labs., Inc., No. 2008-1403, slip. op. (Fed. Cir. Dec. 17, 2010), rev'd, 566 U.S. __ (2012).
The claims at issue had a general format as follows: a method of optimizing therapeutic efficacy for treatment of a disease comprising (a) administering a drug to a subject and (b) determining the level of a metabolite in the subject, wherein a metabolite level less than X indicates a need to increase the amount of drug and a metabolite level greater than Y indicates a need to decrease the amount of drug subsequently administered to the subject (see generally Slip op. at p. 5-6).
The Supreme Court noted that, in Prometheus Labs, (i) the particular drug/disease treatment protocol was already known when the patent application was filed (see Slip op. at p. 9); (ii) the metabolite/disease correlation was already known when the patent application was filed, but the precise levels of X and Y were not known (see Slip op. at p. 4-5; but see p. 21-22); (iii) the "determining" step was broad and not limited to any particular "non-conventional" process (see Slip op. at p. 10, 13, 18, 19); and (iv) the claims did not actually require any subsequent step after determining level of metabolite (i.e., "indicates a need" is at most a suggestion, not an action) (see Slip op. at p. 9, 13).
The Supreme Court characterized the claims at issue as "covering processes that help doctors who use thiopurine drugs to treat patients with autoimmune diseases determine whether a given dosage level is too low or too high." Slip op. at 3. Those claims were summarized as "three steps simply tell[ing] doctors to gather data from which they may draw an inference in light of the correlations" Slip op. at 10-11. The Court ultimately framed the question as "whether the claims do significantly more than simply describe these natural relations [and] 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[?]" Slip op. at 8 (emphasis in original). The Supreme Court answered this with a "no".
In finding that the claims were not patent-eligible, the Court held that the claimed processes have [not] "transformed these unpatentable natural laws into patent-eligible applications" and were thus invalid. Slip op. at 3. This case affirms the principle that "laws of nature, natural phenomena and abstract ideas are not patentable." To be covered by a patent, "an application of a law of nature... must do more than simply state the law of nature while adding the words 'apply it.' It must limit its reach to a particular, inventive application of the law." Slip op. at 1. The instructions for those who administer doses of thiopurine drugs claimed by the Prometheus patents add "nothing specific to the laws of nature other than what is well-understood, routine, conventional activity, previously engaged in by those in the field" and are not patentable. Slip op. at 13.
Despite the clear affirmation that laws of nature are not patentable, the Court provides little guidance as to what makes a method implementing a law of nature (e.g., a medical diagnostic method) patentable or non-patentable. While Prometheus Labs appears not to affect patents covering new drugs and their use or new uses of known drugs (see Slip Op. at p. 18), there is now a grey area concerning process claims that relate to laws of nature. Specifically, it is unclear what additional element or limitation is enough to overcome well-understood, routine, conventional activities related to laws of nature. Until it is better understood how the Federal Circuit and the U.S. Patent and Trademark Office will implement Prometheus Labs (or an Act of Congress intervenes), it is recommended to exercise increased caution in the filing and prosecution of diagnostic method claims, especially where one or more of the four factors in Prometheus Labs described above may apply. In crafting or re-crafting diagnostic method claims to enhance their patentability, it may be helpful to recite particular "determining" procedures (especially where such procedures are "non-conventional") and to avoid the "wherein ... indicates a need" pitfall by reciting an actual post-determining action step.
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