In advance of the U.S. Supreme Court’s review of In re Bilski, the Federal Circuit recently held in Prometheus Laboratories, Inc. v. Mayo Collaborative Services that patent claims directed to medical treatment and diagnostic methods were patentable subject matter because they transformed the human body by the administration of a drug and further transformed the drug itself during analytical tests used to determine the drug’s concentration in the body, and these transformations were central to the purpose of the claimed method. No. 08-1403, 2009 WL 2950232, at *8 (Fed. Cir. Sept. 16, 2009). This decision provides guidance on how the Bilski machine-or-transformation test applies to medical treatment and diagnostic method claims. The expected Supreme Court decision in Bilski, however, could affect how the Bilski test is applied and thus impact whether such claims are ultimately patentable.

The method claims at issue in Prometheus were directed to optimizing a patient’s dosage level of thiopurine drugs used to treat certain autoimmune diseases. Id., at *1-2. The body breaks down thiopurine drugs into various metabolites that have both useful and potentially toxic effects in the body. Id., at *1. Patients on thiopurine treatment regimes are carefully monitored and their thiopurine dosage is adjusted to maximize the therapeutic effect of the drug while minimizing its toxic side effects. Id. Prometheus’s patent claims were directed to a specific three step optimization process. Id., at *1-2. First, a dose of thiopurine is administered to a patient who has an autoimmune disease. Id. Second, a physician determines the level of thiopurine in the patient’s body. Id. Third, based on the amount of thiopurine detected, the doctor receives a warning message indicating whether the dosage should be increased or decreased. Id.

The trial court granted summary judgment of invalidity under 35 U.S.C. § 101 to defendant Mayo because it found that the Prometheus’s method claims were directed to unpatentable correlations between certain thiopurine drug levels, therapeutic efficacy, and toxicity. Id., at *3. The trial court based its decision on three findings. First, the trial court concluded that the first two method steps, the administering and determining steps, were merely non-patentable data-gathering steps required for any use of the thiopurine drug level correlations, and the third step was merely a non-patentable mental step that did not require any change in the dosage but merely warned the doctor. Id. The court found the drug levels themselves, not the warning message, advised the doctor to adjust the dosage. Id. Second, the trial court found that the correlations were “natural phenomena and not patentable inventions because the correlations resulted from a natural body process.” Id. Third, the trial court determined that because the claims cover the correlations themselves, the claims wholly preempt the correlations, which are a fundamental principle, and therefore the claims are not patentable. Id.

On appeal, the Federal Circuit applied its own Bilski machine-or-transformation test and reversed. Id. (citing In re Bilski, 545 F.3d 943, 961-62 (Fed. Cir. 2008)). Under Bilski, a method is patent-eligible if “ ‘(1) it is tied to a particular machine or apparatus, or (2) it transforms a particular article into a different state or thing.’ ” Id. (quoting Bilski, 545 F.3d at 953). Further, the use of a specific machine or transformation of an article (i.e., any composition of matter, such as a drug) must be central to the purpose of the claims; it cannot be “ ‘insignificant extra-solution activity.’ ” Id. (quoting Bilski, 545 F.3d at 961-62).

Turning to Prometheus’s claims, the Federal Circuit found the claimed treatment and diagnostic method patentable because it transformed (1) the human body by administration of a drug and (2) the bodily sample itself by using purification and analytical tests to determine the drug metabolite’s concentration in the body. Id., at *8. Indeed, the court found that methods of treatment are “always transformative when a defined group of drugs is administered to the body to ameliorate the effects of an undesired condition.” Id. Because the claims were transformative, the Federal Circuit did not address the machine branch of the Bilski test. Id.

The appeals court then specifically rejected each of the trial court’s unpatentability findings. Id., at *8–12. First, the Federal Circuit rejected the trial court’s conclusion that the administering and determining steps were merely data-gathering steps. Id., at *9–10. Rather, the court found that the steps were significant parts of “treatment regimes for various diseases using thiopurine drugs.” Id., at *10.

Second, the Federal Circuit found that the claims were not directed to natural processes. Id., at *8. For the administering step, the court found that “[t]he fact that the change of the administered drug into its metabolites relies on natural processes does not disqualify the administering step from the realm of patentability.” Id. “[E]very transformation of physical matter can be described as occurring according to natural processes and natural law.” Id. Medical treatment, however, is not a natural process, and when this process results in “ ‘a chemical or physical transformation of physical objects or substances [it] is patent-eligible subject matter.’ ” Id. (quoting Bilski, 545 F.3d at 962). For the determining step, which involves various purifications and analytic tests used to determined the level of thiopurine metabolites in a sample, the court found this is also transformative and central to the claimed methods. Id., at *9.

Third, with regard to the final warning step, the Federal Circuit agreed with the trial court that this was a mental step, but concluded this fact alone does not negate the transformative nature of the administering and determining steps. Id., at *10. The court stated that “[a]lthough a physician is not required to make any upward or downward adjustment in dosage during the ‘warning’ step, the prior steps provide useful information for possible dosage adjustments to the method of treatment using thopurine drugs for a particular subject.” Id., at *11. The presence of this mental step did not defeat patentability. Id., at *10–11. Finally, because the administering and determining steps were transformative, the appellate court also rejected the trial court’s finding that the claims covered the correlations between thiopurine drug levels, therapeutic efficacy, and toxicity. Id., *11. Therefore it found that “the claims do not preempt natural processes; they utilize them in a series of specific steps.” Id. “Regardless, because the claims meet the machine-or-transformation test, they do not preempt a fundamental principle.” Id.

Legal observers must wait to see whether the Supreme Court’s ruling in Bilski, a case addressing the patentability of business method claims with oral argument scheduled for November 9, 2009, will provide any corresponding support for the Federal Circuit’s determination of what constitutes patentable subject matter.