Today’s Supreme Court Decision Threatens the Patentability of Diagnostic Test Methods

If your business is based on patented diagnostic test methods, you may want to pay attention today’s U.S. Supreme Court opinion in Mayo Collaborative Services v. Prometheus Laboratories, Inc.  In this case, the Court unanimously reversed the Federal Circuit Court of Appeals and held that patent claims directed to a method of determining whether dosage levels of thiopurine drugs used to treat autoimmune disease are ineffective or harmful are invalid.  The Court’s decision was not based on whether the patented method was sufficiently new (i.e., novel and non-obvious), but rather, whether the claims constitute “statutory subject matter.”  Under the Patent Statute, only certain categories of inventions may be patented, namely processes, machines, manufactures, or compositions of matter.  For a copy of the opinion, click here.

Under the Supreme Court’s recent decision in In re Bilski, claims process claims that are directed to “abstract ideas” are unpatentable subject matter.  In contrast, applications of abstract ideas are patentable subject matter.  The test is inherently subjective and provides little guidance to businesses that develop diagnostic test methods.  The Federal Circuit and the Supreme Court applied the same test to Prometheus’ claims and arrived at different conclusions.

The Prometheus patent claims were require the administration of thiopurine drugs to a subject and a determination of the level of the drugs in the subject. The claims recite that specific lower and higher threshold concentrations of thiopurine in the blood indicate a need to increase or decrease the administered dose, respectively.  Although the claims require administration and determination steps, the Supreme Court held that they improperly sought to cover a “natural law.” 

If anything, this decision adds more confusion and less predictability to statutory subject matter issues.  In particular, the Supreme Court repeatedly referred to the novelty of the individual features of the Prometheus claims other than those that recited the “natural law” in determining whether the claims constitute statutory subject matter.  Of course, quite apart from the issue of statutory subject matter, patent claims must be novel and non-obvious to be valid.  However, the Supreme Court disaggregated the Prometheus claims and considered whether their individual steps were novel to arrive at its ultimate holding.  On the other hand, the Federal Circuit did not engage in this analysis.  The steps of “administering” thiopurine drugs and “determining” their concentrations in a subject appear to be concrete and specific, i.e., not merely abstract.  The Federal Circuit stopped there and found the claims to constitute statutory subject matter.  In contrast, the Supreme Court looked at whether the “administering” and “determining” steps were independently novel:

[T]he ‘administering’ step simply refers to the relevant audience, namely doctors who treat patients with certain diseases with thiopurine drugs.  That audience is a pre-existing audience; doctors used thiopurine drugs to treat patients long before anyone asserted these claims.

Slip Opinion at 9.

[T]he ‘determining’ step tells the doctor to determine the level of the relevant metabolites in the blood, through whatever process the doctor or laboratory wishes to use.  As the patents state, methods for determining metabolite levels were well known in the art.

Slip Opinion at 10.

This analysis confusingly conflates the novelty and non-obviousness inquiries with the statutory subject matter inquiry. Notably, the Court relied on an earlier decision in Diamond v. Diehr to support its holding.  In Diehr the Court held that a method that used the Arrhenius equation in a rubber curing process was statutory.  The Prometheus Court said that the Diehr Court “nowhere suggested that all [the claimed] steps, were in context obvious, already in use, or purely conventional.” Slip Opinion at 12.  However, it is not clear that the Diehr Court attempted to determine whether the steps that made use of the Arrhenius equation were known.  Prometheus indicates that such determinations must be part of the statutory subject matter inquiry.

A close read of the Prometheus claims indicates that they might have fared better if they affirmatively required doctors to change thiopurine dosage levels to achieve the recommended blood concentrations of the drugs.  Instead, they merely recite that the threshold concentrations “indicate[] a need” to change the dosages.  However, the Court expressly declined to consider whether such changes to the clam language would have passed statutory subject matter muster.

The issue of statutory subject matter has plagued software companies for some time now.  However, as the Prometheus decision indicates, medical diagnostic method patent holders will now have to worry about whether their patents could survive a statutory subject matter challenge if they are litigated.