After Mayo, Is Patent Law More Restrictive In US Than Europe?

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The United States is known for taking an unusually expansive approach towards patentable subject matter. Compared with Western Europe, for instance, the US has been far readier to grant patents on business methods, medical diagnostic processes, and human genes.

America’s leniency, however, may be ending. In the last decade, the nation’s courts significantly cut back on the types of inventions that can be patented. And the US Supreme Court’s 20 March ruling in Mayo Collaborative Services v. Prometheus Labs., Inc. [pdf] restricts patentability still further. The decision could bar patents on many medical diagnostic methods, personalized medical treatments, and human genes. Depending on how the ruling is interpreted, America’s standard of patentability could become, in some important ways, even stricter than Europe’s.

US law, like that of nations around the world, declares that natural phenomena and laws of nature are not patentable subject matter. No one can patent e=mc2, for instance.

Inventions that apply natural laws or natural phenomena are, however, patentable. One can thus patent a process for turning uncured rubber into moulded rubber products, even though the process uses a law of nature to determine when to open the mould.

But if an invention uses only “well-understood, routine, conventional” acts in order to apply a law of nature, that is basically an attempt to patent the underlying law of nature – and the invention is unpatentable subject matter, the US Supreme Court unanimously held in Mayo. The court applied this reasoning to strike down a patent on a process for using thiopurine in personalized medical treatments.

Thiopurine is known to be an effective treatment for autoimmune diseases, but people vary significantly in their ability to metabolize it. The same dose of thiopurine affects different people differently. As a result, doctors have trouble predicting how much of the drug to administer any specific patient. They know that if the dose is too low, it will be ineffective, and if the dose is too high, the patient can suffer harmful side effects.

The invention at issue in Mayo was a simple process for determining thiopurine dosage: administer thiopurine, then determine the level of thiopurine metabolites in the patient’s blood, and adjust the dosage if the metabolite level is too high or too low. The Supreme Court found that the relationship between the amount of thiopurine metabolites and the effect of thiopurine was simply a law of nature.

The remaining parts of the invention – administering the drug and determining the level of drug metabolites in a blood sample – were just “well-understood, routine, conventional activity already engaged in by the scientific community,” and this was not “sufficient to transform unpatentable natural correlations into patentable applications,” the court held.

Mayo’s ramifications could be far-reaching. The decision could be “a big step towards restricting the scope of patentable subject matter,” said Prof. Rebecca Eisenberg of the University of Michigan Law School.

It could prohibit patents on many other personalized medical treatments. If so, this would bring the US more in line with Europe – which forbids patents on medical treatment.

The ruling also “has the potential to invalidate a large number of diagnostic patents,” said Ned Israelsen, a partner in Knobbe Martens, Olson & Bear. That could put the US in the unusual position of denying legal protection to some inventions – in vitro diagnostic methods – that other countries are willing to patent. “In vitro diagnostics are generally patentable in Europe [and] Japan,” noted Michael Gollin, a partner in Venable.

Mayo may also undermine gene patents. Less than a week after the Supreme Court issued its decision in Mayo, the court vacated a controversial ruling [pdf] that isolated human genes are patentable subject matter and remanded [pdf] the case “for further consideration in light of Mayo.”

The gene patent case, Association for Molecular Pathology v. Myriad Genetics, now goes back to the Federal Circuit (often called the nation’s patent court”). Isolated DNA has been patentable for decades in the US, and many experts expect the Federal Circuit will reaffirm its prior ruling that isolated genes are patentable.

Some experts, however, are not so sure. Prof. Dennis Crouch of the University of Missouri Law School noted on his blog that “Following Mayo, the court could logically find that the information in the DNA represents a law of nature, that the DNA itself is a natural phenomenon, that the isolation of the DNA simply employs an isolation process already well known and expected at the time of the invention, and ultimately that the isolated DNA is unpatentable because it effectively claims a law of nature or natural phenomenon.”

If the US courts rule isolated genes are not patentable subject matter, America’s standard of patentability in this area will be stricter than Europe’s. The European Patent Organization, which has 38 member states, follows the EU’s Biotech Directive, which states that “biological material which is isolated from its natural environment” may be patentable “even if it previously occurred in nature.”

Steven Seidenberg is a freelance reporter and attorney who has been covering intellectual property developments in the US for more than 15 years. He is based in the greater New York City area and may be reached at

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