Background
Hospital Sainte-Justine in Montreal discovered a natural correlation: patients metabolize thiopurine drugs (used to treat inflammatory bowel disease and autoimmune conditions) into metabolites at different rates, and the concentration of those metabolites in a patient’s blood predicts whether the dosage is too low (ineffective) or too high (toxic). Prometheus Laboratories licensed these patents and developed tests and protocols based on the correlations. U.S. Patent Nos. 6,355,623 and 6,680,302 claimed methods of optimizing thiopurine dosing by (1) administering the drug to a patient, (2) measuring the resulting metabolite concentration, and (3) determining whether the dosage should be adjusted.
Mayo Clinic developed its own thiopurine monitoring tests and Prometheus sued. The district court found the claims patent-ineligible as directed to natural phenomena — the natural correlations between metabolite levels and drug efficacy or toxicity. The Federal Circuit reversed, and Mayo petitioned the Supreme Court. The Supreme Court vacated and remanded for reconsideration in light of Bilski v. Kappos (2010). On remand, the Federal Circuit again held the claims patent-eligible.
The Court’s Holding
The Federal Circuit held that the Prometheus patents satisfied § 101. Applying the machine-or-transformation test, the court concluded that the claimed methods were transformative: administering a drug to a patient transforms the human body’s physical state (introducing the drug and resulting in metabolite production), and testing a blood sample to measure metabolite levels transforms the sample into a set of data. These physical transformations, the court reasoned, were sufficient to take the claims beyond mere abstract statements of a natural correlation.
The court acknowledged that the underlying discovery — the natural relationship between thiopurine metabolite levels and drug efficacy — was a natural phenomenon that no one could patent. But the claims, the court said, covered a specific, practical method that used that natural correlation in a real treatment context. The fact that the claims also recited a “determining” step — where a doctor decides whether to adjust the dose — was not sufficient to render the claims invalid, because that mental step was part of a larger, physical method.
Key Takeaways
- The Federal Circuit’s 2010 decision held that diagnostic methods combining physical steps (administering a drug, measuring metabolites) with a mental determination step satisfied § 101 under the machine-or-transformation test.
- A claim that incorporates a natural correlation as part of a larger, physically transformative method process may still satisfy § 101 even if the correlation itself is a natural phenomenon.
- The Supreme Court unanimously disagreed: in Mayo v. Prometheus (2012), it held the claims were directed to a natural law and that adding conventional steps did not make them patent-eligible — establishing the Mayo/Alice two-step framework.
- The Federal Circuit’s Prometheus decision is significant as a historical marker showing the pre-Mayo consensus on how § 101 applied to diagnostic method patents, before the Supreme Court established more demanding requirements.
Why It Matters
The Federal Circuit’s 2010 Prometheus decision and the Supreme Court’s 2012 reversal together constitute one of the most consequential sequences of events in modern patent law. The Supreme Court’s unanimous Mayo v. Prometheus opinion established that natural laws, natural phenomena, and abstract ideas cannot be patented merely by adding the instruction to “apply” them — even through conventional physical steps. This holding had immediate and devastating effects on the diagnostic testing industry, which had relied on the Federal Circuit’s more permissive approach to claim diagnostic methods based on natural correlations.
The tension between the Federal Circuit’s view (physical transformation plus natural correlation = patent-eligible) and the Supreme Court’s view (conventional steps plus natural law = patent-ineligible) created the doctrinal landscape that now governs personalized medicine, biomarker testing, and diagnostic method patents. Thousands of pending and granted patents had to be re-evaluated after Mayo, and the diagnostics industry restructured its patent strategies accordingly. The 2010 Federal Circuit Prometheus decision is the “before” in this story — understanding it is essential to understanding what the Supreme Court changed and why.