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Mayo v. Prometheus: A Facile, and Flawed, Approach to Patent Eligibility

Posted on Wednesday, Apr 4, 2012


A few weeks ago, the Supreme Court issued a decision in Mayo Collaborative Services v. Prometheus Laboratories that promises to significantly disrupt well-established (and investment-backed) expectations in the biotech industry.  Prometheus held patents that claimed methods for calibrating and optimizing the dosage of thiopurine drugs used to treat gastrointestinal and autoimmune diseases.  The methods involved the administration of the drug to the patient and subsequently determining the level of metabolites in the patient’s blood.  The claims identified levels at which the drug was therapeutically effective and above which it might be harmful.  The Supreme Court declared that the patent claims were invalid because they simply “purported to apply natural laws describing the relationships between the concentration in the blood of certain thiopurine metabolites and the likelihood that the drug dosage will be ineffective or induce harmful side-effects.”

Whether you agree or disagree with the ultimate decision, the reasoning is problematic both scientifically and legally.  From a scientific standpoint, what constitutes the effective dose of thiopurines for a particular individual is hardly a “law of nature” akin to the laws of thermodynamics, for instance.  It is, rather, a contingent, individually variable, and empirically determined statistical relationship.   It is also the kind of empirically discovered fact that has long been patentable:  it may be true that the correlation between thiopurine levels, therapeutic efficacy, and toxicity is a natural phenomenon, but so, too, is the fact that bacteria die in the presence of certain compounds, or that materials behave as semiconductors under certain conditions.  Virtually every useful technological advance involves the recognition and application of a natural phenomenon.

It’s this invocation of “law of nature” that makes the decision problematic from a legal standpoint as well.  The Court recognized that “all inventions at some level embody, use, reflect, rest upon, or apply laws of nature, natural phenomena, or abstract ideas.”  The label “law of nature” thus can be hung on many method patents to invalidate them, but the Court provides little concrete guidance for lower courts, lawyers, and businesses to know when to apply it.  We know that Prometheus’ method claims don’t satisfy the requirements of Section 101, but it’s not clear what diagnostic methods might be patent eligible.  The Court expressly declined to provide any guidance:  “We need not, and do not, now decide whether were the steps at issue here less conventional, these features of the claims would prove sufficient to invalidate them.”

The sky isn’t falling.  The Mayo v. Prometheus decision depends to a significant extent on the way that Prometheus’ claims were drafted, and I expect that skilled patent lawyers can write claims in a way that avoids the problems that Prometheus faced.  But the Court’s approach – applying a conclusory label like “law of nature” instead of applying a cogent analysis – is deeply flawed. Blogs