By: Robert R. Sachs, Jennifer R. Bush

In March 2012, the Supreme Court ruled, in Mayo Collaborative Services v. Prometheus Laboratories, Inc., 566 U.S. ___ (2012), that a patent claim on a method of determining whether a given dose of a particular type of medication was safe and effective was a “law of nature” and thus invalid. In the following two-part series, we will show that the Court’s characterization of Prometheus' patent as nothing more than a law of nature does not withstand critical analysis. 

Prometheus Labs is the exclusive licensee of U.S. patents 6,355,623 and 6,680,302. The patents deal with a protocol to determine the safe and effective dosage for thiopurines, which are medications that treat autoimmune diseases such as Crohn’s disease and ulcerative colitis. These medications metabolize in the patient’s body into 6-thioguanine (“6-TG”). The different rates at which the medications metabolize make it difficult for physicians to determine whether a given dose is too high (and thus toxic) or too low (and thus ineffective). The Prometheus patents’ claims identify the range for safe and effective dosages as those which result in a concentration of 6-TG between about 230 pmol and about 400 pmol per 8×108 RBC red blood cells (“RBC”). The patents claim no underlying biological process that accounts for the differences in metabolization.

The Supreme Court ruled that Prometheus’ claims were not eligible for patent protection, holding that Prometheus did nothing more than identify a law of nature. However, The Court’s analysis of the claim as a law of nature is based on a superficial understanding of the scientific status of laws of nature.


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