WASHINGTON, March 20 (Reuters) - The U.S. Supreme Court ruled on Tuesday that Prometheus Laboratories could not patent a diagnostic method to observe changes in a patient's body to determine the best drug dosage for certain diseases, a decision that may affect the future of personalized medicine.
The justices unanimously overturned a ruling by a U.S. appeals court allowing the patent for Nestle SA unit Prometheus for using synthetic thiopurine compounds to treat gastrointestinal disorders such as Crohn's disease and other auto-immune illnesses.
Doctors are told to monitor patients taking the compounds for certain metabolites in red blood cells, with the goal of hitting certain levels to ensure the best treatment with the fewest side effects. Prometheus markets a diagnostic test that uses the technology covered by the two patents.
A unit of the Mayo Clinic, based in Rochester, Minnesota, argued that the method used to determine dosage was akin to a natural phenomenon and thus not eligible to be patented.
The fight began in 2004, when Mayo, which had been a Prometheus customer, said it would begin using its own version of the $260 test. Prometheus sued for patent infringement, and Mayo's test has never come to market.
Mayo won the first round when a district court invalidated the patents. But the U.S. Court of Appeals for the Federal Circuit, which hears patent appeals, twice held that Mayo was wrong and ruled that the method Prometheus came up with was a "transformation" that could be patented.
The Supreme Court's opinion, written by Justice Stephen Breyer, concluded that Prometheus' process was not patent-eligible.
"Our conclusion rests upon an examination of the particular claims before us in light of the court's precedents," Breyer wrote in the 24-page opinion. "We conclude that the patent claims at issue here effectively claim the underlying laws of nature themselves. The claims are consequently invalid."
The case had been closely watched because it could affect the burgeoning personalized medicine field, which involves determining whether a patient is genetically susceptible to a disease and would best respond to certain treatments.
The American Medical Association and 10 other medical groups supported Mayo, while trade groups for the drug and biotechnology industries supported Prometheus.
The Supreme Court case is Mayo Collaborative Services v. Prometheus Laboratories, No. 10-1150.