Mayo Collaborative Services v. Prometheus Laboratories is the unanimous Supreme Court decision that resurrected § 101 as a meaningful patent-eligibility limit on natural laws and natural phenomena. Mayo gave the Federal Circuit and the USPTO the two-step framework that Alice Corp. v. CLS Bank (2014) would universalize two years later — making Mayo the often-overlooked but doctrinally essential ancestor of the modern § 101 motion.
Decided March 20, 2012, 566 U.S. 66.
Background
Prometheus Laboratories owned U.S. Patent Nos. 6,355,623 and 6,680,302, covering methods for optimizing dosage of thiopurine drugs (used to treat autoimmune disease and leukemia) by measuring the level of metabolites in a patient's blood. The claimed steps:
- Administer a thiopurine drug to a patient.
- Determine the metabolite level in the patient's blood.
- Wherein a metabolite level above a threshold indicates a need to decrease dose, and below another threshold indicates a need to increase dose.
Mayo developed and used a competing test. Prometheus sued for infringement. Mayo argued the patents were invalid under § 101 — the claimed correlation between metabolite level and dosing was simply a natural law.
The district court agreed with Mayo. The Federal Circuit reversed, holding that the "administer" and "determine" steps were sufficiently transformative.
The holding
The Supreme Court unanimously reversed the Federal Circuit, holding the claims invalid. Justice Breyer's opinion articulated a two-step inquiry:
[W]e must determine whether the claims at issue are directed to a patent-ineligible concept. If so, we then ask, what else is there in the claims before us? To answer that question, we consider the elements of each claim both individually and as an ordered combination to determine whether the additional elements transform the nature of the claim into a patent-eligible application.
Applied to Prometheus's claims:
- Step 1. The correlation between metabolite level and therapeutic efficacy is a natural law — the human body's metabolism of thiopurines is not a human invention.
- Step 2. The "administer" and "determine" steps were "well-understood, routine, conventional activity already engaged in by the scientific community." They added no inventive concept beyond the natural law itself.
Result: claims patent-ineligible under § 101.
Why Mayo matters more than people remember
Most defendant-side patent lawyers reach for Alice when filing a § 101 motion. But Alice itself adopted the framework directly from Mayo:
[I]n Mayo Collaborative Services v. Prometheus Laboratories, Inc., 566 U.S. 66 (2012), we set forth a framework for distinguishing patents that claim laws of nature, natural phenomena, and abstract ideas from those that claim patent-eligible applications of those concepts.
— Alice, 573 U.S. at 217.
In other words: Alice did not invent the two-step test. Mayo did. Alice extended it from natural laws to abstract ideas — but the doctrine, the "inventive concept" language, and the "well-understood, routine, conventional" gloss all come from Mayo.
Aftermath
After Mayo, the Federal Circuit and lower courts began invalidating life-sciences patents whose only inventive contribution was a natural-correlation discovery. The most-cited applications:
- Diagnostic methods. Claims to "measure X to detect disease Y" are particularly vulnerable. Ariosa Diagnostics v. Sequenom (Fed. Cir. 2015) invalidated a fetal-DNA detection patent under Mayo — over a memorable concurrence by Judge Dyk lamenting the result.
- Personalized-medicine patents. Claims tying treatment decisions to genetic markers face Mayo head-on.
- Software claims. Although Mayo itself is a natural-law case, two years later Alice extended the framework to abstract ideas — covering software and business-method patents. (And Bilski v. Kappos, decided two years before Mayo, had already opened the modern § 101 era by rejecting the Federal Circuit's machine-or-transformation rule as the sole test.)
Pharma and biotech industry groups have lobbied for a § 101 amendment to undo or soften Mayo. So far, no legislation has passed.
What it means for defendants
For most defendants, the operative case is Alice — the abstract-idea branch of the framework reaches software and business-method patents, which are the bulk of troll assertions. But two situations make Mayo itself the lead authority:
- Diagnostic / measurement / detection claims. If the patent's core teaching is "measure X to learn Y," Mayo applies directly.
- Natural-product or natural-correlation claims. Patents on isolated natural substances or on observed natural correlations are Mayo's home turf, post-Myriad (the BRCA case) and Mayo together.
Either way, the analytical structure is the same — name the natural law / abstract idea (Step 1), demonstrate that nothing else in the claim is inventive (Step 2). The doctrinal labels are different; the workflow is identical to an Alice motion.
For software patent assertions, Alice is your motion; cite Mayo as the source of the framework.
Bottom line
Mayo is the unsung Supreme Court case that revived § 101. The two-step test that defendants recite from memory — "directed to a patent-ineligible concept... contain an 'inventive concept'" — is Mayo's framework, not Alice's, and Alice says so explicitly. Any modern § 101 motion should cite both. (US Patent 8,069,073 was invalidated under § 101 in late 2014 — months after Alice but with reasoning rooted in Mayo's framework.)
Read the opinion: Mayo Collaborative Services v. Prometheus Laboratories, Inc., 566 U.S. 66 (2012).
This article is for general education and is not legal advice.