On December 7, 2011, the U.S. Supreme Court heard arguments in Mayo Collaborative Services v. Prometheus Laboratories, Inc. involving whether certain types of medical methods are patent-eligible subject matter. The patents at issue claim methods for optimizing patient treatment in which the level of a certain drug metabolite is measured to identify a need to increase or decrease dosage levels. The district court ruled the claims were invalid, finding the inventors’ discovery was no more than “a natural body process . . . preexisting in the patient population.” The Federal Circuit reversed, holding the claims patent-eligible because they involve a physical transformation and thus are not merely an abstract idea or law of nature. The Supreme Court remanded the case to the Federal Circuit in light of its decision in Bilski v. Kappos, after which the Federal Circuit again ruled in favor of Prometheus.