US Supreme Court Reigns In Patents on Therapeutic and Diagnostic Methods

On 20 March 2012, the US Supreme Court issued its much-anticipated opinion in the case of Mayo Collaborative Services v. Prometheus Laboraties, Inc. The Court has ruled unanimously (9-0) that Prometheus’ claimed method of optimising the administration of a drug by monitoring levels of a correlated metabolite in the patient’s bloodstream amounts to not ‘significantly more’ than a law of nature, and is therefore unpatentable.

The Nature of the Invention

The main claim in the Prometheus patent is directed to ‘a method of optimizing therapeutic efficacy for treatment of an immune-mediated gastrointestinal disorder’. The method involves administering a specified drug, and then determining the concentration of a correlated metabolite in the bloodstream. If the metabolite level is below a lower threshold, the rate of administration of the drug is subsequently increased. However, if the level is above an upper threshold, then the rate of administration is subsequently decreased.

The invention was therefore said to reside in identifying the appropriate range of metabolite concentration, i.e. the lower and upper threshold values. Other than this, the relationship between the drug administration and the metabolite concentration is a naturally-occurring process, and the administration and measurement techniques are well-known and routine.

In considering this, the Court stated that:

Beyond picking out the relevant audience, namely those who administer doses of thiopurine drugs, the claim simply tells doctors to: (1) measure (somehow) the current level of the relevant metabolite, (2) use particular (unpatentable) laws of nature (which the claim sets forth) to calculate the current toxicity/inefficacy limits, and (3) reconsider the drug dosage in light of the law. These instructions add nothing specific to the laws of nature other than what is well-understood, routine, conventional activity, previously engaged in by those in the field. And since they are steps that must be taken in order to apply the laws in question, the effect is simply to tell doctors to apply the law somehow when treating their patients.

In this, the Court clearly considered that the relevant threshold values formed part of the ‘natural law’, and thus could not provide the basis for a patentable invention.


This decision will be of concern to many companies working in the fields of medical therapy and diagnosis, including pharmaceutical and biotech companies working on personalised treatments and medications. In addition to the impact upon future US patent applications, the ruling may call into question many existing granted patents which rely on the use of routine treatment or testing steps. If interpreted too broadly, the decision could lead to the invalidation of a wide range of patents covering therapeutic and diagnostic products and methods, because at a fundamental level the action of all drugs on or in the body is a process following fixed natural laws.

The Court, however, appears to have recognised this risk, placing an important qualification on its decision:

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. For here, as we have said, the steps add nothing of significance to the natural laws themselves. Unlike, say, a typical patent on a new drug or a new way of using an existing drug, the patent claims do not confine their reach to particular applications of those laws. The presence here of the basic underlying concern that these patents tie up too much future use of laws of nature simply reinforces our conclusion that the processes described in the patents are not patent eligible, while eliminating any temptation to depart from case law precedent.

This qualification appears to provide a level of protection for many ‘conventional’ subsequent medical use and method of treatment claims.

The full opinion is available from the US Supreme Court website (PDF, 149 kB).