In a unanimous decision, the U.S. Supreme Court ruled that a patent directed to adjusting a drug dosing regimen based on metabolite levels measured in the patient is not eligible for patent protection under 35 U.S.C. § 101 because it amounts to patenting a law of nature.

Prometheus Laboratories, Inc. is the exclusive licensee of the patents at issue, which protected a method for determining the proper dose of thiopurine drugs to administer to an ulcerative colitis patient by measuring the levels of a particular thiopurine metabolite. Mayo Clinic and Mayo Collaborative Services began using and selling its own test which, although slightly different, was still found at the district court level to infringe Prometheus’s patents. In defense, Mayo asserted that the patents were invalid for being directed to unpatentable subject matter. The district court agreed with Mayo and found that the patents claimed a law of nature and were therefore ineligible for patent protection. On appeal, the U.S. Court of Appeals for the Federal Circuit reversed and found that the patent involved a transformation (drug being converted to metabolite) and that the scope of protection was narrowly defined to a particular area such that it did not preempt all use of the natural process. The Supreme Court disagreed.

Article authored by McAfee & Taft Attorney: Matt Gibson.