Prometheus Unbound: The Untethering of Laws of Nature and Patent Eligibility From Scientific Reality

Vol. 10 No. 1


Robert R. Sachs is a partner, and Jennifer R. Bush an associate, at Fenwick & West LLP.

In March 2012 the Supreme Court ruled, in Mayo Collaborative Servs. v. Prometheus Labs., 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. The Court’s characterization 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 to 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 that result in a concentration of 6-TG between about 230 pmol and 400 pmol per 8 × 108 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 is based on a superficial understanding of the scientific status of laws of nature.


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