Prometheus Laboratories receives a terminal diagnosis from the US Supreme Court

The United States Supreme Court found last week that the claims of Prometheus’ diagnostic method patents were invalid.  The Supreme Court’s decision reversed an earlier decision of the Court of Appeals for the Federal Circuit and in so doing has provided patent applicants and challengers with some guidance on when claims to unpatentable laws of nature might be transformed into patent eligible applications of those laws.  However, the case may call the validity of certain method claims, including diagnostic method claims, into question.  Those who have such claims should reconsider whether they are valid or could be strengthened by amendment.


Prometheus was the exclusive licensee of two patents which claimed a dosage calibration method for thiopurine drugs.  The method claims incorporated the natural relationship between concentrations of drug metabolites in the blood and the effect these concentrations have (ie if concentrations were too low, the drug would be ineffective; if concentrations were too high, the drug would exhibit toxic side effects).  The claims had three key features:

  • An “administering” step (which instructed a doctor to administer the drug to the patient);
  • A “determining” step (which instructed the doctor to measure the metabolite levels of the drug); and
  • A “wherein” step (which described the metabolite concentrations above which harmful side effects would occur, or below which the drug would be ineffective).

The decision of the Court of Appeals held that the method claims of Prometheus’ patents satisfied the “machine-or-transformation” test (as restated in the Supreme Court’s decision of In re Bilski).  The Court of Appeals found that the method claims claimed, in addition to the natural correlation of drug metabolites with toxicity and efficacy, specific treatment steps which were an explicit application of the natural correlation.

The Supreme Court’s decision

The Supreme Court’s unanimous decision held that the method claims were ineligible under section 101 of the Patent Act (35 USC § 101).  The Court noted that implicit in section 101 is the principle that laws of nature, natural phenomena and abstract ideas are not patentable but that the application of such laws (or phenomena or ideas) to a known structure or process may confer patent eligibility.

Despite this, the Supreme Court held that the method claims of Prometheus’ patents did not transform an unpatentable natural law – namely, the relationship between thiopurine metabolite levels and the toxicity or efficacy of thiopurine drug dosages – into a patent eligible application of that law since the additional steps in the claimed methods added “nothing of significance to the natural laws themselves”.  In delivering the Court’s opinion, Justice Breyer stated:

“…the claims inform a relevant audience about certain laws of nature; any additional steps consist of well understood, routine, conventional activity already engaged in by the scientific community; and those steps, when viewed as a whole, add nothing significant beyond the sum of their parts taken separately. For these reasons we believe that the steps are not sufficient to transform unpatentable natural correlations into patentable applications of those regularities.”

The decision demonstrates that the Supreme Court will strike down patents which claim laws of nature, even if they clear the machine-or-transformation test.  The case has been keenly watched by patentees in the United States and comes at an interesting time – it has already had an impact on the Myriad Genetics case, with the Supreme Court ruling this week that this case should return to the Court of Appeals to be reconsidered in light of the Prometheus Laboratories decision.

A copy of the Supreme Court’s decision, Mayo Collaborative Services v Prometheus Laboratories Inc, No 10-1150, can be found here.

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