The Supreme Court unanimously ruled on Tuesday that medical tests that rely on correlations between drug dosages and treatment are not eligible for patent protection.
Writing for the court, Justice Stephen G. Breyer said natural laws may not be patented standing alone or in connection with processes that involve "well-understood, routine, conventional activity."
The natural law in question was the relationship between thiopurines, which are drugs used to treat gastrointestinal disorders, and metabolites in patients' blood. Relying on its research into that relationship, Prometheus Laboratories patented a method to help doctors find the dose that is large enough to work and small enough to cause no needless harm.
After a unit of the Mayo Clinic developed its own test using slightly different correlations, Prometheus sued for infringement of its two patents for its method. Mayo responded that Prometheus was seeking to protect an abstract idea based on natural phenomena that was not eligible to be patented.
In a statement, Prometheus said Tuesday's decision against it "will, in our view, encourage imitation, not innovation."
"Without the availability of patent protection," the statement went on, "future health care will suffer as companies may opt out of new research and development."
A lawyer for Mayo, James A. Rogers III, said the decision "is going to be a benefit for patient care, spur innovation in the field and allow access to good quality diagnostic tests."
In his opinion for the court in the case, Mayo Collaborative Services v. Prometheus Laboratories, No. 10-1150, Justice Breyer started with first principles.
"Einstein could not patent his celebrated law that E = mc2; nor could Newton have patented the law of gravity," he wrote.
The basis for Prometheus's invention, Justice Breyer said, was also a law of nature — "namely, relationships between concentrations of certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove ineffective or cause harm."
The question for the court was whether the use that Prometheus made of this relationship was eligible for patent protection. In general, Justice Breyer wrote, an inventor must do more than "recite a law of nature and then add the instruction 'apply the law.' "
"Einstein, we assume, could not have patented his famous law by claiming a process consisting of simply telling linear accelerator operators to refer to the law to determine how much energy an amount of mass has produced (or vice versa)," he wrote.
Justice Breyer said Prometheus had done essentially the same thing. The company's instructions, he wrote, "simply tell doctors to gather data from which they may draw an inference in light of the correlations."
In holding Prometheus's process ineligible for patent protection, the court struck a balance, Justice Breyer wrote.
"On the one hand, the promise of exclusive rights provides monetary incentives that lead to creation, invention and discovery," he wrote. "On the other hand, that very exclusivity can impede the flow of information that might permit, indeed spur, invention."
Justice Breyer rejected a proposed middle ground that had been offered by the federal government. It had urged the court to rule that the Prometheus method was eligible to be patented as an initial matter but could then probably be challenged as invalid because it was obvious and insufficiently novel.
Justice Breyer said that approach would make "a dead letter" of the exception to patent eligibility for laws of nature.
Just before the argument in the case in December, Prometheus told the court that it had been bought by Nestlé in July. Justice Breyer's wife owned stock in Nestlé, and that would have required his disqualification.
She sold the stock on the morning of the argument, allowing Justice Breyer to sit and to write the court's opinion in the case.
