Supreme Court Decision A Kick In The Gut For Prometheus Labs

The Supreme Court handed down its unanimous decision in the case of Mayo Collaborative Services v. Prometheus Laboratories, Inc. yesterday, finding Prometheus’ patents for a method of administering a drug used to treat gastrointestinal disorders invalid for being directed at unpatetnable subject matter. Prometheus marketed a diagnostic test to Mayo and others that took advantage of a correlation between the administered dose of the drug and the level of certain metabolites that form in the patient’s bloodstream as a result. The test was used by treating physicians to determine if the administered dose was too low to be effective or too high so as to risk negative side effects. Mayo Collaborative Services, a division of the Mayo Clinic, subsequently developed a similar test based on the dose-metabolite correlation and ceased using Prometheus’, at which point Prometheus sued for patent infringement.

It has long been a tenet of patent law that laws of nature are not eligible for patent protection and the classic examples of Newton’s “law of gravity” and Einstein’s “E=mc2” being patent ineligible were reassuringly cited by the Court in this regard. However, an application of a law of nature may be patent eligible within the context of specific structure or process, and Prometheus argued that its patented method which included the additional steps of administering the drug to the patient and determining the patient’s blood metabolite level was such a specific process so as to render the claims patent eligible. The unanimous nature of the decision suggests that the Court had little difficulty finding the dose-metabolite correlation to be a law of nature. The Court stated, “[t]he relation is a consequence of the ways in which thiopurine compounds are metabolized by the body—entirely natural processes.” The additional steps, the Court found, were simply “drafting efforts” designed to monopolize the naturally occurring correlation and that failed to provide any practical assurance that the claimed process is a genuine applications of that correlation. “[S]imply appending conventional steps, specified at a high level of generality, to laws of nature, natural phenomena, and abstract ideas cannot make those laws, phenomena, and ideas patentable.” Consequently, the claims were not directed to patentable subject matter and were invalid. 

For the curious, claim 1 of Prometheus’ U.S. Patent No. 6,355,623 which the Court took as exemplary of the method, reads:

A method of optimizing therapeutic efficacy for treatment of an immune-mediated 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 about 230 pmol per 8×108 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 about 400 pmol per 8×108 red blood cells indicates a need to decrease the amount of said drug subsequently ad ministered to said subject.