Although long-anticipated, the Supreme Court's opinion in Bilski did not provide much in terms of “pellucid” teachings regarding the metes and bounds of patent-eligible subject matter. Against this backdrop, the Court decided last Tuesday to grant certiorari, vacate the Federal Circuit's decision below and remand to the appellate court two cases related to medical diagnostic claims: Prometheus Laboratories, Inc. v. Mayo Collaborative Services and Classen Immu-notherapies, Inc. v. Biogen Idec.1 On earlier appeal, the Federal Circuit decided that the claims in Prometheus were patent-eligible under the “machine-or-transformation” test,2 and that the claims in Classen were not.3 How the Federal Circuit decides these cases on remand, and whether its decision(s) change, will provide the first inklings of how the court will implement whatever insights the Bilski decision may provide.

The types of claims in these cases and the grounds for the Federal Circuit's disparate decisions may be informative. In Prometheus, the claims recited methods for determining whether treatment for immune-related gastrointestinal disorders needed adjustment, i.e. whether the amount of a drug administered to treat the disorder should be changed.4 The asserted claims of the patents-in-suit specifically relate to methods for identifying the administered drug, thiopurine, or metabolites thereof, in red blood cells of a patient.5 Claim 1 of one of the two patents-in-suit was cited in the Federal Circuit opinion as being representative...